January 2014

Delhi
Ophthalmological
Society

Contents

5 Editorial Miscellaneous

Experts’ Corner 51 Prevention of Recurrence of Pterygium: S/C
Mitomycin–C Vs Topical Cyclosporine-A
11 Keratorefractive Surgeries Shakeen Singh, Ripan Wassan, B.B. Dhillon

57 Ocular Involvement in Epidemic Dropsy, a
Serious Concern
Theme: Refractive Surgery Sanjay Teotia

19 ReLEx SMILE-Smiling All the Way Evolution
Luci Kaweri, Ritika Sachdev,
Mahipal Sachdev 67 Evolution of Refractive Surgery
Femtosecond LASIK – Technology and
Machines Hemant Kamble
25 Srilathaa Gunasekaran, Namrata Sharma,
Rajesh Sinha, Tushar Agarwal, PG Corner
Jeewan S. Titiyal
Corneal Inlays: Resurgence of Intra-Corneal 71 Preoperative Workup for LASIK and Phakic
29 Lenses in Presbyopia Reversal IOL
VardhamanP.Kankariya,AlikiN.Limnopoulou, Vijay Kumar Sharma, Tarun Arora
George Kymionis, Sonia Yoo, Ioannis Pallikaris
Aspheric IOLs -Facts & Myth Monthly Meeting Corner
35 J.S. Bhalla, Ankur Singh
77 An Unusual Case of Choroidal Folds
Anisha Seth, Usha K. Raina, Gauri Bhushan,
Neha Goel, Meenakshi Thakar, B. Ghosh

81 An Atypical Motility Presentation

Diagnostics Shagun Sood

43 Topography for the Refractive Surgeon Tear Sheet

Rohit Shetty, Vishal Arora 85 LASIK Complications

Srilathaa Gunasekaran

www. dosonline.org l 3

“It has been said, ‘time heals all wounds.’ I do not agree. The
wounds remain. In time, the mind, protecting its sanity, covers
them with scar tissue and the pain lessens. But it is never gone.”

-Rose Kennedy
“This is a new year. A new beginning. And things will change.”

-Taylor Swift

Respected Seniors & Dear Friends,
By the time you will receive this issue of DOS Times the Annual Conference
of DOS-“OphthaVaganza 2014” will be there at the doorstep. Time flies, but
the memories collected along the way can never be replaced. I have quoted
two beautiful quotes above; each with a different mindset and feelings. We
all face difficult times in life and when we recollect, we feel the same way
as Rose Kennedy had felt some day. But we have to move forward with a
positive mindset and hence the quote of Taylor Swift.
One year has nearly passed since I took over as the Secretary of DOS. We
had some very good times, but we also had tough and terrible times when the
society was in a serious threat. Hence we have some good and bad memories
of the year that has passed. We need to cherish the good ones and keep aside
the bad ones to move forward in the path of progress.
“OphthaVaganza 2014”, the Annual conference of DOS will feature a fusion
of the best in the field of ophthalmology. It will not only feature the best from
different zones of our country but also from far across the globe. This year has
seen a record registration and I would like to congratulate all members for this
feat. It has been the hard work of all Executive members and par excellence
scientific talks presented by the members in past that the annual conference
is drawing larger gatherings each year. We have put great efforts in designing
another such scientific feast for the delegates and hope that this three-day
meet will enrich us in all aspects. I am looking forward to welcoming you at
Delhi and wish you a pleasant stay and an excellent culinary experience as
well.
Sincerely Yours

Rajesh Sinha
Secretary,
Delhi Ophthalmological Society

www. dosonline.org l 5

Delhi
Ophthalmological
Society

Executive Members

J.S. Titiyal MD Rajendra Khanna DOMS Rajesh Sinha MD, FRCS Neeraj Sanduja MS Sanjeev Gupta MD
President Vice President Secretary Joint Secretary Treasurer

[email protected] [email protected] [email protected] [email protected] [email protected]

M. Vanathi MD Vipul Nayar DOMS, DNB, MNAMS Tinku Bali MS, FRCS Bhavna Chawla MS Rajib Mukherjee DOMS, DNB
Editor Library Officer Executive Member Executive Member Executive Member

[email protected] [email protected] [email protected] [email protected] [email protected]

R.P. Singh MD Neeraj Manchanda DO,DNB Manisha Agarwal MS Deven Tuli MS Arun Baweja MS
Executive Member Executive Member Executive Member Executive Member Executive Member

[email protected] [email protected] [email protected] [email protected] [email protected]

Sanjay Chaudhary MS Rajendra Khanna DOMS Harbansh Lal MS Rohit Saxena MD Ashu Agarwal MS
DOS Representative to AIOS DOS Representative to AIOS Ex-Officio Member Ex-Officio Member Ex-Officio Member

[email protected] [email protected] [email protected] [email protected] [email protected]

Experts’ Corner

Keratorefractive
Surgeries

Laser assisted in-situ keratomileusis (LASIK) surgery is the most commonly performed keratorefractive Ioannis Pallikaris
surgery; altering shape of the cornea. Other common keratorefractive procedures to correct low to George Kymionis
moderate myopia include variations of photorefractive keratectomy (PRK) and SMILE. Here we try to Mahipal S. Sachdev
highlight general practice patterns for elective keratorefractive laser surgery based on expert opinion
and consensus. The questions have been prepared by Dr. Tarun Arora (TA) Senior Resident Cornea,
Cataract & Refractive Surgery Services, from R.P. Centre for Ophthalmic Sciences, All India Institute
for Medical Sciences, Ansari Nagar, New Delhi

Dr. Ioannis Pallikaris (IP): MD, Institute of Vision and Optics, University of Crete, Crete,
Greece.
Dr. George Kymionis (GK): MD, PhD, Associate Professor, Department of ophthalmology,
University of Crete, Heraklion, Greece.
Dr. Mahipal S. Sachdev (MPS): MD, is the Director & Senior Consultant, Cataract & Refractive
Surgery of Centre for Sight Group of Hospitals, New Delhi..
Prof. Jeewan S. Titiyal (JST): MD, Professor & Head, Cornea, Cataract & Refractive Surgery
Services, R.P. Centre for Ophthalmic Sciences, All India Institute for Medical Sciences, Ansari
Nagar, New Delhi.
Dr. D. Ramamurthy (DRM): MD, the Director & Senior Consultant at Eye Foundation,
Coimbatore.

TA: What range of refractive errors do you usually treat with LASIK and what is your Jeewan S. Titiyal
age limit for treatment? D. Ramamurthy

IP I treat -8D for myopia. and upto +4 D for hyperopia. Age limit up to 45 years old
for both.

GK: I usually treat 3 to -8D for myopia. Age limit up to 40 years old and+2 to +4D for
hyperopia. Age limit up to 55 years old.

MPS: I treat myopia ranging from 0.5 to 10.0 D, hypermetropia till 6 D (not making
the post-op cornea steeper than 48 D) and astigmatism till 6D with LASIK. Minimum age is
18 years but there is no upper limit.

JST: The refractive error to be treated is never an absolute number, but a dynamic
decision involving the refractive error, central corneal thickness, pupillary diameter and the
elevation maps. Our primary aim is to leave a residual bed of at least 300 µ, to reduce the risk
of having subsequent ectasia. Hyperopia of upto +6 D (SE), astigmatism of -4 D and myopia
of -10 D (SE) is the upper-limit that we have treated so far. I would like to reiterate the fact that
every case has to be individualized.

The lower age limit for LASIK is 18 years and the upper age limit is flexible. The oldest
patient that we have treated is 43 years old. Here, extensive patient counselling and imminent
presbyopia have to be well explained. In these patients, we target emmetropia, rather than
under-correction or mono-vision. We do not perform paediatric LASIK procedures.

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Experts’ Corner

DRM: The range of refractive error that I treat by DRM: If corneal thickness is not a concern, I routinely
LASIK is upto – 10D myopia, +4 D hyperopia and 4D make 120 microns flap. Thicker flaps is a waste of tissue &
astigmatism. Minimum pachymetry for LASIK procedure thinner flaps are more prone for striae, displacement etc.
should be 500 microns and for Surface ablation 450 to 500
microns. JST: In routine cases we prefer having 120 and 110 µ
flaps. The side cut angle for our flap is 700, with a superior
The patient should be above 18 years of age with hinge. These flaps are easy to reposit, rarely curl or fold upon
stable refraction for at least for a year. themselves and have minimal post-operative striae. When
the expected residual bed thickness is slightly less than 300
TA: What is your preffered treatment profile µ, we prefer 100 and 90 µ flaps. With the 200 Hz femto-
for LASIK and do you prefer any particular profile for second LASIK, these flaps are easy to make. However, one
selective cases? has to be gentle during dissection, especially over areas of
anomalous adhesions. Thin flaps have a tendency to recoil
(Topo guided/ Wavefront-guided/ or Wavefront over themselves, and have to be reposited with precaution.
optimized) It is necessary to check that there are no folds in these
flaps intraoperatively with a slit-beam before removing the
IP: Conventional Wavefront optimized treatments. speculum.
I use topoguided selectively in eyes with topographic
abnormalities such as keratoconus (in combination with If corneal thickness is a concern, I make 90 micron
topo PRK), post ablation eccentric zones or central islands. flap with a femto laser.

GK: Wavefront optimized is my preferred profile. I TA: Which corneal topography system do you
use topo-guided treatments in combination with corneal prefer to use in your preoperative workup? What
collagen cross linking for ecstatic corneal diseases such as advantages do you gain from it?
keratoconus.
IP: I am using i-Tracey and Galliley.
MPS: I do wave-front guided ablation for most of my GK: For placid topography I am using i-Tracey
patients as I find that gives optimum correction and better For tomography I am using Galliley.
quality of vision. We do a wavescan pre-op to measure the MPS: I use the Pentacam (Oculus) for corneal
higher order aberrations and accordingly incorporate their topography which uses a Scheimpflug camera for imaging
correction in our laser treatment profile. the anterior segment. It uses corneal elevation data as the
basis of measurements and is a very sensitive, accurate and
JST: In our routine cases we perform a Wavefront reliable tool for pre and post-refractive surgery evaluation
optimized treatment, and have achieved satisfactory of the cornea. Apart from pachymetry and keratometry it
results. In patients with larger pupil size ( > 6 mm) and provides anterior and posterior corneal elevation maps
with previous night vision problems, a wave-front guided which help to identify patients at risk for ectasia or with
treatment is preferred. For re-treatments, we prefer form-fruste keratoconus and helps to reliably exclude them.
Custom-Q (corrected for asphericity) treatments. We have Its Belin-Ambrosio enhanced ectasia displays further help
the Alcon® Wavelight Refractive suite at R P Centre, (AIIMS) to identify at-risk patients. I also find it a versatile instrument
with and integrated Topolyzer for topography guided LASIK for measuring the true-net corneal power, anterior chamber
as well as the Analyzer for wavefront guided treatments. depth and volume, IOP correction and lens status.
JST: We use the Orbscan IIz and Pentacam routinely
DRM: In normal eyes, wave front optimized profile in all our patients. The preliminary screening, pupillometry
is my treatment of choice. When patients have abnormal and WTW measurements are obtained using Orbscan,
cornea, I choose the topo guided treatment. Where HOA a combined placido-disc and slit-scanning device. The
>0.4 microns & patient is symptomatic I offer wave front Pentacam, a Scheimpflug imaging based device provides
guided treatment. valuable information about the posterior elevation,
which is absolutely necessary to rule out sub-clinical
TA: What is the routine flap thickness? What ectasia. The refractive maps as well as the Belin Ambrosio
advantages and disadvantages do you observe with it? Enhanced Ectasia display are seen, to rule out forme-fruste
keratoconus.
IP: 100μm, it gives more residual bed thickness. DRM: I use Pentacam for the pre – operative
GK: From 90-100μm, it is appropriate thickness, work up and I see the following advantages with it:
so that the residual bed thickness is optimized and flap Reliable information about anterior & posterior floats, no
stability is not compromised. extrapolation of data centrally, fairly reliable curvature &
MPS: I routinely do femto-laser LASIK where the flap thickness maps, useful for topo guided treatment on the
thickness is 100 microns which allows me greater tissue Wavelight platform, Belin Ambrosio display (BAD) for
saving while the flap cut with the femto-laser gives good
stability and faster healing. In the last 1 year I have been
doing ReLex SMILE procedures which is essentially a flap-
less LASIK. Since no flap is created, incidence of flap related
complications like flap folds or displacement is nil.

12 l DOS Times - Vol. 19, No. 7 January, 2014

Experts’ Corner

detecting borderline keratoconus,fairly reliable data in post technique very reliable in my hands with minimum post-op
refractive surgery cases. haze and stable refractive correction.

TA: What is your routine post-operative regime JST: Professional history and patient requirement
post LASIK and post PRK? are of great importance in considering surface ablation.
Sportsman, patients targeting armed forces and patients in
IP: Combination of dexamethasone and adventure sports are good candidates, as flap displacements
chloramphenicol for one week. are a real risk in these patients. It is important to choose a
patient with low to moderate myopia as myopic regression
GK: Combination of dexamethasone and and haze are a definite problem with surface ablation. We
chloramphenicol for two weeks in LASIK and for four often do alcohol assisted PRK (20 % concentration ) with
weeks tapering in PRK. mitomycin C 0.02 % application for 12 seconds. Recently
we have shifted to T-PRK that is removal of epithelium with
MPS: I use an antibiotic for 1 week, low intensity the laser itself in PTK mode and than ablation with desired
steroids for 3 weeks, lubricants for 2-3 months post-LASIK. treatment profile. This gives an advantage of speedy healing
For PRK I use an oral and topical NSAID in addition for and less pain. Some amount of haze can still be expected.
immediate post-op pain till the bandage contact lens is A bandage contact lens is a must. Pain and watering are
removed and epithelium grows back. more than in LASIK and epithelial healing takes 2-5 days in
these patients.
JST: A fourth generation fluoroqinolone like
preservative-free moxifloxacin hydrochloride 0.5 %, gives DRM: Indications for surface ablation include corneal
a good cover against the gram positive and gram negative thickness between 450 - 500 microns, refractive error less
bacteria. Moxifloxacin is instilled immediately after the than -6D /+3D, small powers but involved in contact
surgery and then on TDS basis for a month. We prefer to sports or military personnel, family history of keratoconus
use prednisolone 1% as phosphate salt, as it is available in normal individuals, normal corneas with few doubts
in a solution rather than a suspension. It reduces the about topographic evidence of keratoconus.
whitish drug depositions on eyelashes, reducing patient
inconvenience. We start with a 6 times a day dose, reducing My prefered technique is TRANS epithelial PRK.
it to four times a week after 1 week looking at the clinical The problems experienced with a surface ablation
response, and then taper it over a month’s time. As dry eye procedure are pain,irritation watering for 2-3 days, need
and foreign body sensation are common after LASIK, we to wear CL for 2-3 days, abscence of immediate WOW
prefer preservative free lubricant topical eye-drops 6 times factor, more time for refractive outcome to stabilize, haze
a day. The frequency is reduced after 1 month to 4 times & regression.
a day. Cyclosporine is not administered on routine basis.
TA: Do you find any difference in doing hyperopic
DRM: In Post LASIK patients, I prescribe topical LASIK? Is there any difference in outcomes and patient
Loteprednol & 4 th generation fluoroquinolones qid for 1 satisfaction in these cases?
week and non preserved tear substitutes qid for 2-3 months.
IP: Visual recovery is delayed, however patient
In Post PRK, BCL is placed for 3 days or till satisfaction is actually more.
reepithelialisation is complete. I prescribe 4th generation
fluoroquinolones qid for 1 week, Loteprednol qid for 4 GK: I dont perform hyperopic LASIK more than four
weeks & slow taper over next 1 month and non preserved dioptres, as the visual recovery is considerably slower.
tear substitutes for 3 - 6 months.
MPS: In hyperopic patients, I tend to treat closer to
TA: In what cases do you prefer surface ablation? the dilated refraction. Intra-op I create a larger flap (usually
Which is your preferred technique and what problems 9.2mm) with pocket off. Post-op the recovery takes a little
do you find to be associated with it? longer in these patients but after 3-4 weeks, most of the
hyperopic patients are fairly satisfied and happy with the
IP: Diopteric corrections < 3D myopia, eyes with improvement.
Thin corneas (<500u) and normal topography. In my
practice I perform almost 50% surface ablations. JST: Patient selection is important, as the keratometry
is steepened in these eyes after LASIK. Pre-operative
GK: Thin corneas < than 500m, we use epithelial keratometry should be assessed, and a K reading of more
rotatory brush for epithelial removal during surface ablation. than 44 should be avoided. We choose the manifest
refraction in hypermetropes as well. The patient should be
MPS: For patients with a normal topography but counselled that some amount of refractive error may return
corneal thickness between 460 to 490 microns I perform as the amplitude of accommodation reduces with age. The
surface ablation. I use the hockey stick to debride the ablation zone is larger, and hence the flap is also bigger.
epithelium, perform the excimer laser correction followed Sometimes, it may reach the para-limbal area, causing
by Mitomycin 0.02% application for 20-60 seconds bleeding from the limbal arcade. Also, problems with
depending on the amount of refractive error. After copious
irrigation I then apply a bandage contact lens. I find this

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Experts’ Corner

night time driving are more pronounced in these patients. Belin Ambrosio enhanced ectasia display on Pentacam
DRM: There is no difference in procedure although is necessary in all these patients. Ablation ratio, ablation
depth, corneal depth and the total vertical fibres (flap and
I find greater chances of residual error,regression and excimer ablation) are increasingly being considered as
decentered treatment in these cases. risk factors for post-operative ectasia, and we like to take
these factors into consideration as well. In patients where
TA: What is your protocol for treating residual expected RBT is < 300 µ, consider going for a thinner flap.
refractive errors post LASIK? Surface ablation is another consideration in such cases.

IP: By lifting the flap, I have lifted flaps more than 15 DRM: The presence of the following are considered
years after primary LASIK. Red flags : family history of keratoconus, scissoring reflex
on refraction, high non orthogonal cylinders, unstable
GK: Six months postoperative interval, I am treating refractive error & BCVA < 20/20, thin corneas, abnormal
residual refractive errors by lifting the flap. topography.

MPS: I wait 3 months before performing any re- TA: How frequently do you see progressive
do surgeries to allow the refractive error to completely corneal ectasia post LASIK? How do you manage these
stabilize. Once I have a stable topography and refraction I patients?
obtain 3 fortnightly readings which are repeatable and plan
a re-do. I always try and re-lift the flap and I find that one IP: 1 out of 15,000 cases.
can lift the flap even many years after the primary surgery I manage these patients with CXL.
has been performed. If the flap cannot be lifted, I perform GK: 1 out of >5000 cases. They are managed with
a PRK. CXL with or without comination with topoguided PRK.
MPS: The incidence of ectasia is reported to be
JST: We wait for a period of 3-6 months for the ranging from 0.04 to 0.6%. I see not infrequently referred
refractive error to stabilize after the primary procedure. patients from various parts of the country who have primary
In patients presenting late, it is important to distinguish LASIK surgery performed elsewhere and develop ectasia.
ectasia from myopic regression and keratometry should After a complete evaluation I perform corneal cross linking
be thoroughly assessed. Corneas undergoing refractive with /without intra-corneal ring segments, usually as a
surgery are oblate with positive spherical aberrations. simultaneous procedure to provide maximum benefit. Post-
Normal cornea has -0.3 to -0.4 asphericity. So we prefer to operatively contact lenses maybe prescribed to optimize
use Custom Q, or asphericity corrected treatments in these the vision.
patients. A word of caution is to assess the RBT thoroughly JST: Fortunately the post LASIK ectasia incidence is
as Custom Q treatments ablate more than the routine very less but being a tertiary referral centre we do see quite
wave-front optimized treatment and the ablation depth has a number of cases.
to be adjusted for the same. In post-operative period, it is Whenever a patient with a drop in CDVA comes
important to carefully look at epithelial ingrowth. to us, myopic regression and ectasia are two important
considerations, and need to be distinguished from each
DRM: I wait for at least 3 months & ensure that the other. Apart from documenting vision and refractive
residual power & topography is stable. Then relift the flap error, keratometry and elevation maps are very important.
& treat on the bed. Myopic refractive error with increased astigmatism, worse
spectacle-corrected visual acuity, increased corneal toricity
TA: What all preoperative evaluation is necessary with topographic abnormality, and progressive corneal
to prevent the risk of postoperative ectasia? thinning are hallmark of post- LASIK ectasia that needs to
be assessed over a time period.
IP: Topogragraphy and tomography both. Checking progression and visual rehabilitation are
GK: Both topographic and tomographic evaluation the cornerstones of management. Cases with more than
with corneal pachymetry. 400 µ central corneal thickness are good candidates for
MPS: A good pre-op work up is essential. Make sure CXL. We have facilities for both accelerated and the routine
the refractive error is stable, there is no family history of CXL. Currently we are doing an epithelium off CXL with
keratoconus, age is over 18 years and the patient is not 0.1% riboflavin in 20 % Dextran with 3 mW/cm2 for 30
pregnant. Then we perform a pentacam and scan the anterior minutes. It is important to note that while debriding the
and posterior corneal elevation maps, the pachymetry and epithelium, the sweeping movement should be initiated
keratomtry. Finally we look at the BAD display. I donot from the hinge area, going in the opposite direction. In
plan excimer ablation more than 100 microns and leave a doubtful cases, epithelium on CXL is a good option.
residual corneal bed closer to 300 microns.
JST: Steep keratometry (> 47 D), high and
asymmetrical astigmatism, frequent change in refractive
error, skewed axes on topography maps, thin cornea,
and asymmetric topography - all should raise a suspicion
of predisposition to ectasia. A thorough screening with

14 l DOS Times - Vol. 19, No. 7 January, 2014

Experts’ Corner

DRM: Very rarely these days with careful preop patients get cyclosporine eye drops and lubricants for
evaluation. Management would be CXL, Glasses,CL. atleast 3 months.

TA: Do you use ReLEx and SMILE technique in GK: Most common complaint is dry eye, We use
your practice? If yes, in what cases and what advantages cyclosporine eye drops and lubricants for first 3 months.
do these procedures have over LASIK?
MPS: Most common complaint is dry eye and such
IP: No. patients benefit from extra lubrication for 3-6 months post-
GK: No. op. Patients with higher corrections sometimes complain of
MPS: I have been using ReLEx and SMILE for the glare and haloes in the evening when their pupil dilates. I
last 1 year and have performed over 1000 procedures. I usually prescribe a pupil stabilizing (alpha agonist) eye drop
recommend them for all patients with a myopic refractive in the form of brimonidine 2 hours before they step out or
error up to 10 D. Since no flap is created, I find the cornea drive at night. Some patients are steroid responders and
is very stable and flap –related complications such as may develop high IOP even after a few days of steroid use
striae or flap folds do not occur. Incidence of DLK is also leading to haze and a drop in vision. These patients need
minimal. Since corneal tissue is removed from a small to be differentiated form DLK as the treatment is exactly
2clock hour incision, the corneal nerves are not transected opposite, namely withdrawing steroids in the former and
and incidence of dry eye is negligible. adding steroids in the latter.
DRM: No,I don’t.
JST: We do not have ReLEx SMILE facility at our JST: Dryness and night time blurring, haloes and
centre. glare are the most common complaints. Pre-operative and
post-operative counselling is a must in all the cases for
TA: Have you combined LASIK with accelerated commonly anticipated problems. In symptomatic patients
C3R (LASIK XTRA) in your practice? If, yes, for which with dry eye, but without any evident punctate staining
cases? we increase the frequency of lubricants and advocate a
gel formulation for night time use. In severe cases, 0.05 %
IP: No. cyclosporine is our drug of choice.
GK: No.
MPS: I offer LASIK XTRA to patients who I feel are DRM: Dry eye: treat with non preserved lubricants,
at risk for ectasia such as patients with a refractive error Residual ref error : if patient is bothered by it & enough
between 8-10 D or those who are otherwise fit for refractive tissue available I’ll do enhancement procedure. Patients
surgery but have a family history of ectasia or keratoconus. with abnormal topography, I perform a topo guided
JST: No, we haven’t yet tried LASIK XTRA in our treatment and in DLK, interface wash.
patients.
DRM: Yes. The indications are: Young age, Thinner TA: How frequently do you see infections in
corneas, Mildly doubtful topography, Higher powers post LASIK cases? What are the commonly isolated
especially hyperopia & astigmatism. organisms in these cases and in what time period do
they present?
TA: What is your experience with presbyopic
correction? What difficulties do these patients face IP: I have personally not encountered post LASIK
postoperatively? infection.

IP: I use variety of methods (Monovision using LASIK GK: None of my patients have suffered from post
or CLE, multifocal/ accommodative IOL – crystalens AO, LASIK infections as yet.
W-IOL and corneal inlays)
1 case with atypical mycobacterium infection after
GK: We use variety of methods, however my LASIK was referred to me.
preferred is Monovision using LASIK.
MPS: Post LASIK keratitis has a very rare occurrence
MPS: NIL. as the UV light of the excimer laser has a sterilizing effect.
JST: Currently we do not employ any keratorefractive Diagnosis can be missed especially when atypical micro-
procedure for presbyopia correction. organisms such as acanthomeba or fungi are the cause.
DRM: None.i Don’t do Laser vision correction for With use of femto-LASIK the incidence has further dropped
presbyopia. as no micro-keratome comes in contact with the eye. The
organism usually comes from the ocular flora of the patient,
TA: What are the common complaints that though instruments, sponges and the surgeon may be the
patient face post LASIK in your practice and how do source. Gram positive bacteria and atypical mycobacteria
you manage those? are commonly isolatedand the reported incidence by
ASCRS is around 0.035%.
IP: I guess most common complaint is dry eye. My
JST: R.P. Centre being a tertiary referral centre we do
see all types of post operative cases including infections.
We have seen early as well as late onset of infectious

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Experts’ Corner

keratitis in post LASIK patients. In 2005 and 2006, we laser,replace flap,wait for 3 months & treat by PRK or with
have published fungal infection with Alternaria and early flaps thicker than on the first occasion.
infection with Pseudomonas aeuroginosa respectively.
We have recently seen an interface fungal infection with TA: Do you find any difference in the outcomes
Fusarium, 9 years after the initial LASIK. On an average of microkeratome assisted and Femtolaser assisted
we get 3-4 referred cases of post-LASIK infection per year. LASIK?
Early infections are more common than late infection,
bacterial keratitis predominating over fungal and atypical IP: There is probably no difference in refractive
mycobacterial infection. outcomes, but FS LASIK gives more safety and flap stability
in my opinion.
DRM: I have seen a single unilateral case of infection
in my practice of LASIK over 17 years. GK: Yes, especially in term of safety.
MPS: Femto-laser is definitely a safer and more
TA: How frequenly do you see flap related advanced way to perform LASIK. The iLASIK femto-laser
complications and interface related problems in your creates planar flaps which are more consistent with a
practice? How do you manage those? smoother tissue separation. The flaps are cut at an acute
angle which makes them less prone to displacement with
IP: Flap and interface related complications are very fewer incidence of microstriae and greater flap stability
rare now a days with femtosecond lasers and also due such that they can withstand high gravitational forces. With
to new generation microkaretomes. Probably the most the introduction of flap-less LASIK with ReLEx SMILE, flap
common still is mild DLK (diffuse lamellar keratitis), which complications have become a thing of the past. The greater
we manage with increasing steroid dosage. stability, superior refractive correction and minimum
incidence of DLK makes femto-LASIK the procedure of
GK: Very rarely after the introduction of femtosecond choice for all my refractive patients.
laser. If at all, very few cases of DLK, which were managed JST: Yes, definitely. The rates of intra-operative flap
with steroids. related complications like free cap and buttonholes have
definitely gone down. In past 1000 eyes that we have
MPS: Flap related complications and DLK have operated, we haven’t noted a single free cap. So, Femto-
become minimal with the use of flapless LASIK (ReLEx laser assisted LASIK is useful in patients with keratometry
SMILE). When referred from other areas, I normally < 40 D and steeper than 47 D.
manage them by re-lifting the flap, irrigating the interface, On the flipside, we had a few cases with vertical
straightening out the folds with or without epithelium gas breakthrough with Femto-Laser assisted LASIK. Loss of
debridement depending on whether they are fixed or not. suction during flap creation has been seen in a couple of
Distilled water to loosen the adhesions is used and ironing cases. These have been managed by taking 20 µ thicker
out the folds with a warm spatula maybe needed in resistant flaps, larger by 0.5 mm in size. Opaque bubble layer is
cases. A BCL is applied at the end of the procedure. DLK another finding not seen in microkeratome assisted LASIK.
is managed by frequent topical and oral steroids in mild Rarely, it may involve the centre cornea and interfere with
to moderate cases but severe cases need a flap-re-lift and pupil tracking.
wash to remove the inflammatory cells. Though literature reports increase in DLK incidence
with Femtosecond assisted LASIK, we haven’t seen a
JST: Microstriae and DLK are the most common significant rise in its incidence at our centre.
flap related complications. For, microstriae grade 1- 3, we DRM: Femto laser assisted LASIK is better.
prefer to start topical corticosteroids on two hourly basis,
monitoring the glare, contrast, aberrations and vision. In DOS Correspondent
these patients functional visual acuity than Snellen’s visual Tarun Arora MD
acuity is always a concern. Resolution of symptoms is quite
common with increase in corticosteroids. For macrostriae
and grade 4 microstriae not amenable to steroid therapy,
PTK is a good option. Sometimes, refloating, stretching and
repositing the flap are considered. Refractory cases may
call for suturing the flap edge.

DRM: I rarely see flap complications even less
with femtoflaps. The following is the management for
various flap related complications: Striae - if in visal axis
hydrate & smoothen the flap, flap displacement - replace
the flap in position, interfaces debris & DLK - interface
wash, epithelial ingrowth - lift the flap & debridement if
progressive, free flaps - if adequate bed proceed with laser
& replace flap, flap tears or inadequate flaps - postpone

16 l DOS Times - Vol. 19, No. 7 January, 2014

RefracRtievfreactSivue Srugregerryy

ReLEx SMILE-Smiling Luci Kaweri
All the Way MD

Luci Kaweri MD, Ritika Sachdev MS, Mahipal Sachdev MD
Centre For Sight, Safdarjung Envlave, New Delhi

Refractive lenticular extraction (ReLEx) is the latest the visual recovery is delayed, and there is a hyperopic
development in the long evolution of keratolenticular over shoot for the first postoperative month. In some
refractive procedure1. Small incision Lenticule Extraction patients, especially higher myopes, it is seen that excimer
(SMILE) is minimally invasive and innovative procedure. laser PRK is followed by corneal haze and regression of
The refractive lenticule cut is performed using the state the treatment. Today, despite significant improvements in
of the art Femtosecond laser and the lenticule is extracted laser ablation profiles, medication and wound – healing
through small corneal incision. During the last 2 years, this modulation regimens, and surgical technique, excimer
most advanced LASIK procedure, has become clinically laser PRK is performed on less than 20% of all refractive
available in Europe and Asia as an alternative to LASIK for surgery patients.
correction of myopia. In the United States, the procedure is In the early1990s, the work of Burratto et al3 and Pallikaris
currently undergoing clinical trials for approval by the US et al4 married the concept of ALK with the excimer laser in
Food and Drug Administration. to a procedure known as laser-assisted in situ keratomileusis
Travelling the path (LASIK).
In the past lamellar keratoplasty and automated lamellar Laser-assisted insitu keratomileus involves using a
keratoplasty were used to treat myopic refractive error. mechanical microkeratome to fashion a hinged flap of the
They involved the removal of a lenticule from the corneal cornea, with a thickness of 130 to160 microns. Excimer
stroma to flatten the central cornea and thus correct myopia laser reshaping was performed on the exposed corneal
using a mechanical microkeratome. Although introduced stroma and the hinged flap was then refloated back on the
by Barraquer2 in the 1950s, it was only in the late 1980s cornea and allowed to heal in place without any sutures.
and early 1990s where in microkeratome reached a level Although LASIK with the mechanical microkeratome is very
of refinement. However, because of higher complications popular with surgeons, the mechanical microkeratome is
with mechanical microkeratomes, LK techniques remained associated with most of the complications of LASIK, like
niche techniques to treat high myopia and never became buttonhole flaps, incomplete flaps, irregular flaps, and flap
part of the ophthalmic mainstream. displacements. In addition, mechanical microkeratomes
The excimer laser was introduced in 1983 and was used sometimes make flaps that are inadvertently too thick,
on human eyes to reshape the cornea from 1988 by a which leads in some cases to keratectasia5,6, a progressive
procedure known as photo refractive keratectomy. It thinning and subsequent irregular steepening of the cornea.
involved mechanical scraping of the corneal epithelium Mechanical microkeratomes have improved during the
followed by reshaping of the remaining corneal bed years.
with the excimer laser. It obtained US Food and Drug However, many surgeons have now adopted the
Administration approval in 1995 and quickly became the femtosecond laser7 as their primary means to make LASIK
procedure of choice to treat refractive errors. flaps. The introduction of a femtosecond laser to make
However, because the corneal epithelium is removed, the LASIK flaps has the advantages of making more predictable
patient experiences pain during the first post-operative day, and safer flaps and relatively aberration neutral flaps.

www. dosonline.org l 19

Refractive Surgery

Figure 1: VisuMax Laser System Figure 2: The innovative corneal
interface concept

However, it also has some disadvantages. There is a need • Age: Should be older than 18 years.
for two lasers to complete the procedure, namely, the • Ocular history: No signs of lens changes, glaucoma,
femtosecond laser to make the flap and the excimer laser
to perform the laser ablation of the refractive lenticule. This or other ocular problems. Any retinal breaks or holes,
leads to significant extra capital and maintenance costs should be treated before the procedure.
and the consumable and license fees for two lasers. There The machine
is also significant work flow disturbance within the laser The VisuMax Femtosecond laser8 is used to perform ReLEx
suite, with the surgeon and the patient moving from one SMILE procedure (Figure 1). The VisuMax is capable
laser to another. of creating refractive lenticules within the cornea with
The femtosecond laser can be used to carve out a lenticule high degree of accuracy. The VisuMax software allows
within the corneal stroma. The lenticule can then be the calculation of the refractive lenticule needed for
extracted from within the corneal stroma, either by creating the correction of a particular refractive error and it also
and lifting a hinged flap similar to LASIK or by extricating automates all stages of the procedure.
it using a small incision in the cornea. These techniques of Technique
femtosecond lenticule extraction are known as femtosecond Under aseptic conditions and topical anesthesia, patients
lenticule extraction (FLEx) and small-incision lenticule are prepared in a manner usual for LASIK. A standard
extraction (SMILE), respectively. Both techniques represent speculum is used to keep the eye open. In the VisuMax
all-in-one femtosecond laser refractive surgery because they Laser System, the laser system remains fixed, whereas
represent novel integrated surgical techniques to perform the patient position can be aligned by adjustment of the
corneal laser surgery in a single step and need only one position of the patient bed with a joystick. The patient’s eye
laser to perform laser refractive surgery and have various is positioned under a curved contact glass interface during
clinical, practical, and economic advantages over the more the operation of the femtosecond laser and it is positioned
traditional two-laser solution. under a surgical microscope integrated into the system
Selection criteria during the phase of surgical manipulation. The eye view is
Currently ReLEx SMILE is available to treat myopic errors relayed to the surgical microscope eye pieces in both cases
of up to – 10D spherical equivalent, with or without to allow for full visual control during the entire procedure.
astigmatism of up to – 5D. It is at present not available for A sterile curved contact glass is attached on to the laser
hyperopic correction. Patients are generally selected using system optical aperture, and the patient is positioned some
the same criteria as LASIK. distance below it. The patient is then asked to look a tab
• Corneal topography: To rule out forme fruste linking fixation light, and the patient’s eye is adjusted in
relation to the contact glass interface. The surgeon monitors
keratoconus, pellucid marginal degeneration and whether the centration is appropriate. After the surgeon is
posterior keratoconus. convinced that the centration is correct, suction is initiated
• Pachymetry: Thickness less than 480 microns or where to hold the cornea against the contact glass interface
the thickness of the cornea is likely to be less than 400 (Figure 2).
microns after the procedure are contraindicated.

20 l DOS Times - Vol. 19, No. 7 January, 2014

Refractive Surgery

Figure 3: Photodisruption by femto laser Figure 4: Tissue disruption planes

Once the contact interface is fixed, delivery of the surface of the refractive lenticule, which is extended by
femtosecond laser pulses is initiated. Femtosecond laser about 0.5 mm beyond the optical zone desired; and finally
pulses with typical pulse energy of less than 200nJ are (d) 30 to 50 degrees in corneal length from the surface of
delivered with a pulse repetition rate of 500 kHz. Each the cornea, with a depth up to the edge of the anterior part
femtosecond laser spot creates a photodisruption within the of the lenticule. The entire procedure takes less than 30
cornea that initiates a chain of events that eventually results seconds, practically independent of the refractive error to
in a small volume of corneal tissue being converted into a be corrected. The spherocylindrical shape of the lenticule
gas bubble (Figure 3). If several millions of such pulses are generated thus is designed to correct for refractive errors.
laid down, a tissue disruption plane is created within the The anterior surface of the lenticule can be programmed to
stroma as each gas bubble disrupts the corneal tissue at its be 100 microns or more below the corneal surface, similar
respective position. It is possible with the VisuMax laser to to the flap thickness in LASIK. The lenticule diameter can be
create 3 - dimensional free - form incision plane anywhere 5 to 7mm while treating myopia and myopic astigmatism.
within the cornea, with a precise shape. The minimum thickness of the lenticule edge is 10 to15
In these cases, 4 different tissue disruption planes are microns to support easier manual manipulation of the
created for the procedure (Figure 4). These include (a) lenticule edge. In SMILE, the side cut incision can be 30
the posterior surface of the refractive lenticule, with a to 50 degrees.
pre- programmed diameter based on the optical zone Once the femtosecond laser cutting procedure (treatment
selected (b) the 360 – degree corneal length vertical edge mode) is finished, the suction is automatically switched
of the refractive lenticule, with a depth equivalent to the off, and the patient’s eye is released from the contact glass
thickness of the edge of the lenticule; (c) the anterior and moved under the microscope (observation mode).
The side cut incision is generally created superiorly or
superotemporally to preserve the nasal and temporal nerve
arcades and to provide surgical convenience. A small sharp-
tipped instrument is used to open a small portion of the
side cut incision. A small blunt spatula is inserted into the
side cut incision, and the anterior surface of the lenticule
is separated from the overlying cornea. A small sharp
instrument is then used to enter the tissue disruption plane
on the posterior side of the lenticule to separate the edge of
the lenticule. A blunt spatula is then inserted through this
edge below the lenticule and used to separate the posterior
part of the lenticule from the underlying stroma. Once the
lenticule is free from both surfaces, a small microforceps
is inserted to grasp the lenticule and extract it from the
corneal stroma. A 24 - gauge cannula is inserted into the
incision and the corneal pocket is flushed with balanced
salt solution. APVA spear is used to wick off excess fluid
from the side cut incision (Figure 5). After 30 seconds, the
speculum is removed. Both eyes can be treated at the same
time.

www. dosonline.org l 21

Refractive Surgery

Figure 5: Surgical steps anterior lenticule surface from the overlying cornea;
the wrong plane is selected by the surgeon and the
Femto Laser assisted posterior part of the lenticule is separated instead. In
(a) Posterior tissue disruption plane (lenticule cut) this case, the lenticule is stuck on the undersurface of
(b) Anterior tissue disruption plane (Flap cut) the flap rather than on the stromal bed. In case this
(c) Superior flap side cut incision is not possible, the VisuMax allows the creation of a
Manual side cut incision only and it is best to convert the case
(d) Delineation of planes into FLEx by repeating a 280- to330-degree side cut
(e) Dissection of planes incision.
(f) Lenticule removed 3. In many cases, a fine scarring is observed at the flap
Post operative treatment edge or the lenticule edge. However, this is outside
Steroids and antibiotics for 1-2 weeks and artificial tear the pupillary zone and is visually non significant.
supplements for a period of 4 to 8 weeks after the procedure. Some patients, especially chronic contact lens users
Complications before the procedure, experience dry eyes after the
1. Suction loss wherein the contact glass and cornea procedure. This is less frequent than the occurrence of
dry eye symptoms after conventional LASIK9.
become detached during the procedure, may occur 4. Similar to any other refractive surgery procedure,
due to the patient squeezing the eye or moving there is likely to be a need for enhancements after the
suddenly. Fluid ingress between the suction ports of procedure. Currently, enhancements after FLEx and
the contact glass and the cornea, gas bubble migration SMILE must be completed either by using an excimer
and subsequent compressive forces against the contact laser PRK or by lifting the flap, and performing excimer
glass. laser corneal reshaping.
In the event of suction loss, the VisuMax automatically Therearenootherseriousintraoperativeorpostoperative
goes into a restart mode based on the stage of the complications. Vertical gas breakthrough10, transient
procedure at which the suction loss occurred. The light sensitivity syndrome11 or rainbow glare12 are
general challenge in this situation is re-docking of almost never seen.
the contact glass interface to the eye while retaining Advantages over Femto-LASIK
centration. Sometimes, the pupil is obscured by the 1. There are economic, clinical and workflow advantages
gas bubbles, making this difficult. Depending on the of performing only Femtosecond procedures like ReLEx
stage at which the suction loss occurs, the restart mode SMILE over Femto-LASIK in terms of saving on capital
repeats both femtosecond passes, only the flap pass, or costs, maintenance costs and consumable costs.
only the side cut incision. In our experience, repeating 2. In ReLEx, the lenticule is carved out within the cornea
the treatment immediately is convenient and does not by cutting action, as opposed to ablation with excimer
seem to affect the results of the procedure. laser which depends on a number of other factors
2. The second intra-operative complication that is like corneal hydration levels, atmospheric humidity
generally observed is while trying to separate the and temperature and also on the depth in the stroma
at which ablation occurs. The scatter in the ablation
rates is particularly high, when ablation depth is
large as in cases of higher refractive error. Because
of the femtosecond lasers cutting action, the scatter
in the thickness of the lenticule is minimized and it is
independent of the refractive error being treated.
3. The refractive predictability with the ReLEx procedure
is higher than with an excimer laser, particularly for
higher amounts of refractive errors.
4. With femtosecond laser, the peripheral loss of fluence
is not a factor at all and no compensation needs to
be carried out. So the amount of tissue required per
diopter of treatment is smaller than that required with
an excimer laser which compensates for the peripheral
energy loss.

22 l DOS Times - Vol. 19, No. 7 January, 2014

Refractive Surgery

5. The total amount of energy laid down into the cornea 4. Pallikaris IG, Papatzanaki ME, Siganos DS, et al. A corneal flap
is also much less than with an excimer. Since there are technique for laser in situ keratomileusis: human studies.Arch
some evidences that the fast heat generated by excimer Ophthalmol. 1991;109:1699-1702.
laser has some adverse effect on corneal healing, the
low energy used in ReLEx SMILE is a welcome benefit. 5. Binder PS. Ectasia after laser in situ keratomileusis. J Cataract Refract
Surg. 2003;29:2419-429.
6. The small incision heals relatively quickly, causes less
patient discomfort and little risk of flap displacement. 8. Binder PS. Analysis of ectasia after laser in situ keratomileusis: risk
factors. J Cataract Refract Surg. 2007;33:1530-38.
7. The small flap diameter and the small side-cut incision
means that there is smaller likelihood of cutting corneal 7. Ratkay-Traub I, Ferincz IE, Juhasz T, et al. First clinical results with
nerves, perhaps leading to less problems of dry eyes. the femtosecond neodynium-glass laser in refractive surgery.J Refract
Surg. 2003;19:94-103.
8. Finally, the procedure saves working time as there is
no time loss in switching patients from one laser to 8. Blum M, Kunert K, Gille A, et al. LASIK for myopia using the Zeiss
another. VisuMax femtosecond laser and MEL 80 excimer laser.J Refract Surg.
2009;25(4):350-56.
References
9. Sekundo W, Kunert K, Russmann C, et al. First efficacy and safety
1. Rupal Shah, MS, Samir Shah, MTech, MS, and Hartmut study of femtosecond lenticule extraction for the correction of
Vogelsang. All-in-One Femtosecond Laser Refractive Surgery Tech myopiaSix Month Results. J Cataract Refract Surg. 2008;34:1513-20.
Ophthalmology 2011;9: 114-21)
10. Seider M, Ide T, Kymionis G, et al. Epithelial breakthrough during
2. Barraquer JI. The history and evolution of keratomileusis. Int Intralase flap creation for laser in situ keratomileusis. J CataractRefract
Ophthalmol Clin. 1996 Fall;36(4):1-7. Surg. 2008;34:859-63.

3. Buratto L, Ferrari M, Rama P. Excimer laser intra stromal 11. Stonecipher KG, Dishler J, Ignacio TS, et al. Transient lightsensitivity
keratomileusis. Am J Ophthalmol. 1992;113:291-95. after femtosecond laser flap creation: clinical findingsand
management. J Cataract Refract Surg. 2006;32:91-94.

12. Bamba S, Karolinne R, Ramos-Esteban J, et al. Incidence of rainbow
glare after laser in situ keratomileusis flap creation with a 60
kHzfemtosecond laser. J Cataract Refract Surg. 2009;35:1082-86.

Congratulations

Many congratulations to Prof. Yog Raj Sharma for being
appointed the new chief of Dr. Rajendra Prasad Centre for
Ophthalmic Sciences, All India Institute of Medical Sciences,
New Delhi. Prof. Y.R. Sharma is an eminent Vitreoretinal Surgeon
of the country. He has been working as a faculty at A.I.I.M.S.
for last more than 30 years. Before joining Dr. R.P. Centre,
A.I.I.M.S., he was working as a faculty at the School of Medicine,
Yale University, USA. He has many notable achievements as a
Surgeon, Academician and Researcher. We wish him luck for
his future endeavours.

www. dosonline.org l 23

Femtosecond LASIK – Refractive Surgery
Technology and Machines
Srilathaa Gunasekaran
MD, FAICO

Srilathaa Gunasekaran MD, FAICO, Namrata Sharma MD, Rajesh Sinha MD,
Tushar Agarwal MD, Jeewan S. Titiyal MD

Rajendra Prasad Centre for Ophthalmic Sciences,
All India Institute of Medical Sciences, New Delhi

Femtosecond LASIK is fast becoming the standard of to increase the firing frequency from the initial 6 KHz to
care for correcting mild to moderate refractive error. 500 KHz3,4. Currently five femtosecond laser platforms are
Since the time it was first available commercially in 2001, available across the world (Table 1) and they differ primarily
the technology of femtosecond for flap making in LASIK in pulse energy and frequency, applanation surface (flat or
is progressively advancing allowing short time, better curved), laser delivery (raster or spiral pattern), available
customization of flaps in terms of size, shape, side cut applications and mobility (Table 2)5. Apart from the
angle and additional procedures like creation of channels LASIK flap creation, there is a wide range of procedures
for Intra Corneal Ring Segments (ICRS) and keratoplasty. that can be performed with the femtosecond laser which
includes laser assisted capsulotomy, incision placement
Physics of Femtosecond laser and nucleotomy in cataract surgery, Astigmatic Keratotomy
(AK), Channel creation for placement of Intra Corneal Ring
The femtosecond laser works based on the principle of light Segments (ICRS), intrastromal lamellar pocket creation for
induced optical breakdown (photo ionization). It is a solid the insertion of corneal inlays for presbyopia, femtosecond
state Nd Glass laser similar to Nd YAG laser in the infrared lenticule extraction (FLEX), Small Incision Lenticule
range of 1000- 1053nm, and the pulses produced are for Extraction (SMILE), Intrastromal Presbyopia Correction
very short duration of femtoseconds (10-15 seconds). It is (INTRACOR), crafting a precise, interlocking graft host
because of this very short pulse duration that the collateral junction for penetrating keratoplasty and for creating donor
damage produced to the surrounding tissue is nearly lamellar buttons for both anterior and posterior lamellar
absent. When the high number of photons concentrated keratoplasty5.
in each laser pulse interact with electrons in the stromal
tissue, vapourisation of the tissue occurs producing a Table 1: Currently available femtosecond laser platforms
microplasma / cavitation bubble1. Each cavitation bubble Currently available femtosecond laser platforms
contains CanOd2 and water and the gas within the microplasma • Intralase (Abbott Medical Optics Inc, Santa Ana,
expands coalesce with the adjoining ones with only
thin tissue bridges separating them which are easily broken California)
using spatula during a flap lift. This process of application • Femtec (20/10 Perfect Vision, Heidelberg,
of short duration pulses at a specific depth in the stromal
tissue produces a cleavage plane for flap lift. Slower lasers Germany)
(nanoseconds or picoseconds) have shown to produce • Femto LDV (Zeimer Ophthalmic Systems, Port,
larger cavitation bubbles, greater shock waves to the
surrounding tissue and more collateral damage, hence not Switzerland)
developed for photodisruption2. • VisuMax (Carl Zeiss Meditec AG, Jena, Germany)
• Wavelight FS 200 (Alcon Laboratories Inc, Ft
Various machines and hardware differences
Worth, Texas)
Since the time this femtosecond technology was introduced,
gradual technological advancements have taken place

Refractive Surgery

Table 2: Comparison of commercially available femtosecond lasers5

Parameter Intralase i150 Femto LDV Zeiss Visumax Femtec 20/10 Wavelight FS 200
Amplifier Oscillator -
Laser type Amplifier Oscillator Fibre optic amplifier
amplifier 1053 1045
Spiral Raster
Wavelength (nm) 1053 1045 1043 mechanical Computer
Visual Visual and virtual
Laser pattern Raster Segmental Spiral

Centration Computer mechanical mechanical

Visualisation of Visual and virtual Virtual Visual
surgery

Mobile No Yes No No No
Single built in Dual built in
Suction Single syringe Single built in Single built in on
limbus

Applanation planar Planar Curved Curved Modified planar
surface

Additional AK, wedge, LK, PKP, pocket, FLEX, SMILE, LK, AK, LK, PKP, AK,LK, PKP, ICRS
procedures LK, PKP, ICRS, ICRS, ICRS, PKP ICRS, INTRACOR
biopsy, pocket

Figure 1: Wavelight refractive Suite • 1050 Hz multi-dimensional eye tracker with a latency
of 2 milliseconds.
Wavelight Refractive suite
Wavelight FS 200 (Figure 1) produced by the Alcon • Wavefront Optimized treatments result in a large true
Laboratories Inc (Fortworth, Texas) is FDA approved and aspheric optical zone and a functional transition zone.
commercially available since 2010 and has the following This results in better mesopic and scotopic vision.
features:
• The world’s fastest platform, combining a 500 Hz • FS 200 kHz laser creates a 9.0 mm flap in 6 sec., total
procedure time, “suction on” to “suction off” ~30 sec,
excimer laser and a 200 kHz femtosecond laser allows flap centration adjustment after docking.
• Customized, patient-specific treatments - Wavefront
• Other treatment options available include: Sub-
Optimized, Wavefront - Guided, Topography-Guided, Bowman Keratomileusis, Intracorneal ring segments,
Custom - QTM and PTK treatments available (Table 3) Lamellar and penetrating keratoplasty.
• Technology - leading ablation times of just 1.4 seconds
per diopter iFS – Intralase Femtosecond LASIK
• Has WaveNet, an integrated network which allows This was the first machine commercially available for
seamless data transfer. femtosecond flap making. Since then, the machine has
advanced in the speed of femtosecond laser and ablation
profiles and currently the fifth generation machine is
available. Following are the features:
• The iFS laser (Figure 2) has two major innovations

in flap architecture: the inverted bevel – in side cuts
upto 150 degree for better biomechanical stability
and elliptical shaped flaps for maximal stromal bed
exposure.
• This laser also allows the creation of intrastromal
channels for ring segments and keratoplasty.
Carl Zeiss – Visumax
Visumax (Figure 3) is the only laser that allows the treatment
by refractive lenticule extraction for SMILE (Small Incision
Lenticule Extraction) procedure. It is the fastest femtosecond

26 l DOS Times - Vol. 19, No. 7 January, 2014

Refractive Surgery

Table 3: Various excimer ablation profiles available in Wavelight EX500

ABLATION PROFILE FUNCTION

Wavefront optimised Aspheric ablation profile, maintains asphericity of the cornea

Wavefront Guided (A - CAT) Ablation based on the wavefront map of the patient, indicated where RMS
> 0.3µ

Topo – guided (T – CAT) (Topolyser) Topo guided LASIK specifically indicated for enhancement procedures,
irregular corneas

Topo – guided (T – CAT) (OcuLink) Same as Topolyser guided T – customized ablation treatment (CAT) except
that the data used is from scheimpflug based topographer

Custom Q (F – CAT) For fine correction of refractive errors to achieve a target Q value for the
patient’s cornea

Figure 2: Intralase iFS done. Depending on the type of the laser a flat or curved
contact surface is used. A flat contact lens simplifies the
laser that is currently available (500 kHz). Specific features creation of planar dissection however it requires a higher
include: level of suction and greater increase in Intraocular Pressure
• Curved applanating surface available in three different (IOP) which can temporarily reduce the vision during flap
making. Curved applanation surface provides a better
sizes (small, medium large) to ensure an optimal fit approximation to the cornea with less suction required
with the cornea leaving the patients’ visualization unhindered during the
• Short treatment times with pulse frequency of 500 kHz process of flap making. However curved contact surface
Surgical technique makes the creation of planar flaps more technologically
Since the flap making and the excimer ablation are computer challenging and suction loss may occur more readily
controlled, data regarding the desired flap diameter, depth, with the eye movement. Currently available femtosecond
hinge location its angle and side cut angle, patient’s platforms take 10 – 40 seconds to create a lamellar corneal
refractive error are entered first. After anaesthetizing the flap and this does not include docking and undocking
ocular surface with topical proparacaine eye drops, suction times as it varies widely with the surgeon’s experience. The
ring is placed to stabilize the eye and for the seating of sequence in which a FS flap is created includes the creation
applanation plate. Once the suction is achieved, the of a canal / pocket first followed by the hinge and then the
applanation cone (patient interface) is inserted and docking bed cut and finally the side cut. Many systems allow the
flap position to be changed even after docking to achieve
centration. After flap creation, the flap is then lifted using a
blunt spatula. Since the tissue bridges are inherently present
in the femtosecond created flap, it takes little more time
and effort to lift the flap compared with a microkeratome
created flap. The excimer laser ablation and further steps
are the same as for a standard LASIK procedure.
Femtodynamics
Femtodynamics refers to using various intraoperative clues
and postoperative outcomes to modify the laser settings
and techniques to optimize the outcomes6. The pattern of
OBL, the ease or difficulty of flap lift, the appearance of
peripheral side cut and the presence or absence of DLK
provide useful clues whether too much or too little energy is
being delivered to the cornea. One parameter is changed at
a time and atleast 2 successive treatments must be assessed
before further modifying the laser parameter.
Femtosecond Vs Mechanical microkeratome
Femtosecond flaps are planar compared to the meniscus
shape flaps created with microkeratome. The flap thickness

www. dosonline.org l 27

Refractive Surgery

Table 4: Comparison of Microkeratome and Femtosecond lasers for LASIK flap creation5

Parameter Microkeratome Femtosecond Laser

Flap shape Meniscus Planar

Flap / hinge diameter Keratometry dependent Computer control

Flap thickness Dependent of pachymetry, Keratometry, Computer control
Intra Ocular pressure (IOP), blade quality
and translational speed

Thickness predictability Moderate High

Side cut Shallow angled Computer control

Epithelial in growth More than femtosecond laser flaps Less

Unique complications Flap buttonhole Opaque bubble layer, vertical gas
breakthrough, transient light sensitivity
syndrome, rainbow glare

Figure 3: Carl Zeiss Visumax in femtosecond flaps act as a barrier to epithelial cells
is consistently within 10 micron of intended thickness. preventing complications like flap displacement, epithelial
The flap can be created over a wide range of thickness ingrowth. No differences have been noted with regard to
profile compared to only a few modifications possible the final visual outcome in the various studies (Table 4).
with the microkeratome. The increased side cut angle References

1. Chung SH, Mazur E. Surgical applications of femtosecond laser. J
Biophotonics. 2009;2(10): 557 – 572

2. Liu X, Elner VM et al. Photodisruption in the human corneas as a
function of laser pulse width. J Refract Surg. 1997; 13: 653 – 658

3. Ratkay – Traub I, Juhasz T, Horvath C et al. Ultra short pulse
(femtosecond) laser surgery: initial use in LASIK flap creation.
Ophthalmol Clin North Am;14(2): 347 – 355

4. Binder PS. Femtosecond applications for anterior segment surgery.
Eye Contcat Lens. 2010;36(5): 282 – 285

5. Kymionis GD, Kankariya VP, Plaka AD et al. Femtosecond laser
technology in Corneal Refractive Surgery : A Review. J Refract
Surg.2012;28(12):912 – 92

6. Faktorovich EG. Femtodynamics: Optimising Femtosecond Laser
settings and procedure techniques to optimize outcomes. Int
Ophthalmol Clin. 2008 Winter;48(1):41-50

The Agenda of General Body Meeting held at 13th April, 2014 on 4:30 PM
of Delhi Ophthalmological Society at Banquet Hall, Ashok Hotel, Chanakyapuri, New Delhi

The Agenda of the General Body Meeting shall be : 7. Ratification of New Members.
1. Confirmation of the minutes of the previous Annual 8. Presentation of Awards and Momentoes.
9. Announcement of election results.
General Body Meeting held on 25th August, 2013. 10. Address of the outgoing President.
2. Adoption of the annual report of executive committee 11. Installation of incoming President.
12. Address of incoming President.
presented by Hony. Secretary. 13. Suggestions & Resolutions for General Body Meeting.
3. Financial highlights by Treasurer. 14. Any other matter with the permission of the Chair.
4. Report of Library officer. 15. Vote of thanks by Secretary.
5. Report of Editor DJO.
6. Report from Representative to AIOS.

28 l DOS Times - Vol. 19, No. 7 January, 2014

RefracRtievfreactSivue Srugregerryy

Corneal Inlays: Resurgence of Intra-Corneal Vardhaman P. Kankariya
Lenses in Presbyopia Reversal MD

Vardhaman P. Kankariya MD1,2,3, Aliki N. Limnopoulou MD, MSC2,
George D. Kymionis MD. PHD2, Sonia H. YOO MD3, Ioannis Pallikaris MD2

1. Sai Surya Eye Care and LASIK Centre, India; 2. Institute of Vision and Optics, Greece;
3. Bascom Palmer Eye Institute, USA

The necessity to develop a minimally invasive, safe and inlay with this mechanism is the Flexivue Microlens
potentially reversible technique for the compensation (Presbia, CA, Netherlands).
of presbyopia in plano, presbyopic patients aged 45-60 History of Intracorneal Lenses
years old, who are considered too old for laser corneal Jose Barraquer in 19492 first described the implantation of
refractive surgery and too young for cataract operation, a synthetic lenticule inside the cornea for the correction
led to the development of a new modified monovision of aphakia and high myopia. The technique was known
approach where intracorneal phakic inlays are implanted as Synthetic Keratophakia. Those premature intracorneal
into an intrastromal corneal pocket in the non-dominant inlays were composed of glass and plexiglass. These high-
eye of the patient. The intracorneal pocket is either index polymers were used due to their optical abilities
created mechanically with a microkeratome or with the in order to treat high myopia3. Their limited permeability
femtosecond laser. Major advantages of the procedure are of fluids, nutrients and products of cells’ metabolism,
the easy surgical technique, the potential reversibility and led to anterior stromal thinning of the cornea, stromal
the ability to combine with several surgical corneal and opacities and keratolysis. In the literature, the results of
intraocular modalities for the correction of refractive errors the experimental use of intracorneal inlays from synthetic
and presbyopia1. polymers as glyceryl methacrylate4 and later on from
Types of Current Corneal Inlays
The current utilized intracorneal inlays for the treatment of Figure 1
presbyopia can be categorized into three groups according
to their mechanisms of action:
1) Intracorneal inlays that reshape the anterior surface of

the cornea, increasing its curvature, making the tissue
steeper. Those inlays are made of hydrogel and an
example inlay with this mechanism of action is the
Vue+ inlay (ReVision).
2) Intracorneal inlays made of Polyvinylidine Fluoride
(PVDF) that act as small apertures increasing the depth
of focus through a pinhole effect. An example inlay
with this mechanism of action is the Kamra inlay
(AcuFocus).
3) Intracorneal inlays made of Hydrophillic Acrylic that
serve as a refractive addition lens, creating a bifocal
optical system in the patient’s cornea. An example

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Refractive Surgery

Figure 2

Figure 4

Figure 3 thickness, made from hydrogel, with an addition refractive
power and a central opening permitting flow of fluids and
hydrogel5, revealed that hydrogel as a material of choice for nutrients to the anterior central cornea. This inlay was
the creation of intrastromal inlays. It was semi permeable implanted into a stromal pocket created by a mechanical
to the fluids and nutrient ingredients for the cornea, but microkeratome. The Microlens was later named In Vue
had limited optical properties due to its low optical index which represents the former inlay of the Flexivue inlay
of refraction. (Presbia, Amsterdam, Netherlands).
The PermaVision Intracorneal Lens (Anamed, Lake Forest, Details of Current Designs
CA) was made from a hydrogel-based material called Current intracorneal inlays for the compensation of
Nutrapore. It had a diameter ranging between 5.0 to 5.5mm, presbyopia in emmetropic, presbyopic patients that are
with central thickness of 30 to. 60 mm. Its mechanism of utilized are CE marked and are under the United States
action was to alter anterior cornea’s surface curvature to Food and DrugAdministration (FDA) trial. They consist
treat ametropia and presbyopia by creating a multifocal of the KAMRA inlay (AcuFocus, Irvine, CA), the Vue+
pattern on the tissue’s surface. Similar mechanism of action (ReVision Optics, Lake Forest, CA), and the Flexivue
was recorded for the Intra Lens (Lake Forest, CA) and the Microlens (Presbia, CA, Netherlands).
current Vue+ inlay (ReVision Optics, Lake Forest, CA). KAMRA inlay by AcuFocus (AcuFocus, Inc. Irvine, CA)
The Intracorneal Microlens (BioVisionAG, Bruggs, The KAMRA inlay by AcuFocus (AcuFocus, Inc. Irvine, CA)
Switzerland) was a lenticule of 3.0mm diameter and 20mm is a small aperture corneal inlay for treatment of presbyopia
in emmetropic, presbyopic patients that utilizes the pinhole
effect to increase depth of field by selecting for central light
rays only. The Kamra inlay has an outer diameter of 3.8mm,
a central annulus of 1.6mm that serves as pinhole and 5μm
thickness. It is made of bio-compatible polyvinylidine
fluoride (PVDF) and is implanted inside a corneal pocket at
200μm stromal depth, created by the femtosecond laser. It
also has eight thousand four hundred laser-etched openings
of 5.5 to 11.5u in order to allow the metabolic flow to the
anterior cornea, distributed in a designed pseudorandom
pattern. Also, a combined implantation of the Kamra inlay
with simultaneously performed LASIK to treat ametropia
and presbyopia has been described. In that case, the inlay

30 l DOS Times - Vol. 19, No. 7 January, 2014

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Figure 5 Figure 6

is placed under a corneal flap at 200μm depth after the received European Conformity (CE) mark in the European
ablation, in order to relieve the patient from glasses for Union and has recently completed the first phase of US
far and near activities. Examination of ocular structures, FDA clinical trials.
diagnostic tests and visual fields measurement are not Sharma et al8 reported results on eight emmetropic,
affected by this procedure. presbyopic eyes who underwent implantation of the inlay,
Seyeddain et al6 reported two years data on the AcuFocus under corneal flap created with a microkeratome. All eyes
inlay implanted in 32 eyes and stated that 96.9% of implanted revealed a 20/32 or better unaided near vision,
patients could read J3 or better in the operated eye with two years postoperatively. All patients recorded that they
mean binocular uncorrected near acuity of J1 and mean were satisfied with the outcomes of the procedure and
binocular uncorrected distance visual acuity of 20/16. were able to perform typical near activities without glasses.
Yilmaz et al7 reported 12 months results on 39 presbyopic Slade et al presented the six months results of the inlay
patients where12 of them were naturally emmetropic and implantation in natural or post refractive emmetropes,
27 had emmetropia resulting from earlier LASIK. At one presbyopes at the ASCRS Meeting in 20109. Mean UVA
year, the mean uncorrected near visual acuity of the patients for near was 20/25 and no patient lost two or more lines
participating in the study, improved from J6 preoperatively regarding far vision. Invue lens, (Biovision AG, Brugs,
to J1+. The mean uncorrected distance visual acuity Switzerland) is another corneal inlay which is implanted
in the operated eyes did not change significantly from inside a corneal pocket of the non dominant eye created
preoperatively and remained 20/20 throughout the using a mechanical microkeratome. Bouzoukis et al10
monitoring period. reported improving visual acuity for near with 20/32 UNVA
The Vue+ corneal inlay in 98% of the patients.
The Vue+ corneal inlay, formerly known as the Presbylens The Flexivue Microlens (Presbia, Amsterdam,
(ReVision Optics, Lake Forest, CA) is a permeable hydrogel Netherlands) intracorneal inlay
lenticule with a refractive index similar to the human The Flexivue™ Micro-Lens is a transparent, hydrophilic
cornea. The inlay has a diameter of 2mm, is approximately disc with 3 mm diameter and approximately 15 μm edge
10-μm thick at the periphery and has a thickness from 24 thickness. The central 1.6 mm diameter of the disc is
to 40μm at the central part. The inlay is inserted under plano and the peripheral zone has an add power. The base
either a LASIK flap or into a corneal pocket at a depth of power available range from +1.5 D to +3.50 D in 0.25
approximately 120 to 130mm in the non dominant eye of D increments. At the center of the disc there is a hole of
the patients. Its mechanism of action includes alteration 0.15mm diameter that permits the transfer of oxygen and
of the anterior surface of the corneal curvature, to create nutrients of the cornea through the lens. The Microlens is
a multifocal cornea that improves near and intermediate inserted into a stromal pocket created with the femtosecond
visual acuity, with slightly affecting distance visual acuity. laser with an insertion device into the non dominant eye
The constriction of the pupil during near tasks offers an concentric with the estimated line of sight.
additional pseudo accommodative help. The Vue+ has

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Figure 7 such as Corneal topography and tomography are must to
rule out corneal astigmatism. As all of them have a modified
The lens has a bifocal optical system which acts as a monovision approach, determination of ocular dominance
modified monovision (smart monovision). During far by preferential looking test is a must and usually we give
vision the rays pass through the central zone of the inlay them a contact lens trial of monovision, to know their
without refractive effect and will be sharply focused on the acceptance.
retina, whereas the rays which pass through the refractive Surgical Technique
peripheral zone will be not of focus in front of the retina. Intracorneal inlays may be implanted inside a corneal
During near vision, the rays which pass through the central stromal pocket or under a lamellar corneal flap. The
zone will be out of focus behind the retina and the rays implantation of the intracorneal inlay inside a corneal
which pass through the lens peripheral refractive zone will pocket,provides several advantages. The majority of
be focused on the retina. As a result, only the peripheral peripheral corneal nerves are preserved, resulting in
zone of the lens provides the near vision correction, and unaffected corneal sensitivity and potentially faster visual
affects far vision, whereas the central zone of the lens and recovery of the patients. Pocket procedures also allow
the peripheral unaltered part of the cornea do not affect the the preservation of the biomechanical properties of the
far vision. cornea, offering stable mechanical stability of the tissue.
In a study of 43 patients (average age, 52 y) with a mean Additionally complications concerning corneal flap
preoperative UCDA of 20/20 and mean UCNA of 20/50, creation as striaeand free cap are avoided. On the contrary,
all patients had an increase in the uncorrected near visual the creation of a corneal flap permits simultaneous ablation
acuity after 1 week. By 1 year, 93% of patients had an of the stromal tissue with the excimer laser, in order to treat
UCNA of J2 or better (Limnopoulou, Pallikaris et al,2012). refractive errors along with presbyopia. Also, a corneal flap,
Indication allows easy manipulations during a potential reposition or
Corneal inlays are procedure of choice for Plano removal of the inlay. It is important to mention that since
presbyopic patients. These group of patients can be 1. proper centration of an intracorneal inlay to treat presbyopia
Natural planopresbyopes 2. Post LASIK planopresbyopes is vital for its better performance, a main difference from
3. Post cataract surgery Plano presbyopes. It can also be the standard procedure of creating a LASIK flap, is that an
implanted in ametropic presbyopic patients by performing irrigation of the stromal bed is avoided prior to the flap
excimer laser ablation and corneal inlay in the same sitting, repositioning, in order to inhibit a potential replacement of
either both under the flap or the inlay is implanted in the the lenticule.
deep pocket. During the last decade, in the field of refractive surgery
Pre-Operative Work Up there has been an increasing interest in the use of corneal
All patients must undergo an extensive pre-operative work inlays for the treatment of presbyopia by either using flaps,
up similar to any refractive surgery patients, including created by mechanical microkeratomes11,12 or femtosecond
vision (unaided distant and near), manifest refraction lasers13, or by using pockets created by mechanical
(distant and near), IOP, Corneal and anterior segment microkeratomes or femtosecond lasers14. Compared to the
biomicroscopy, Retinal evaluation. Ancillary investigations mechanical technique, the femtosecond laser makes tunnel
creation faster, easier and more reproducible as well as
offering precise tunnel dimensions (width, diameter and
depth) compared to manual techniques, helping in better
centration of inlay. This could enhance the predictability,
resulting in better final outcomes and improving the safety
of the procedure. The development of special softwares for
customized pockets has further simplified and increased
the efficacy of the procedure.
An additional advantage of the procedure is that is not needed
to change or to add new equipment in a modern refractive
surgery center, except the special injector and the mask,
offering also one more application in the femtosecond laser
treatments. The inlays are implanted only in non dominant
eye and centration is most crucial. I prefer to center them
on excimer laser microscope and ask the patients to focus
at the focusing light, so as to know the line of sight. And the
inlay is implanted and centered on line of sight. Acutarget

32 l DOS Times - Vol. 19, No. 7 January, 2014

Refractive Surgery

is a sophisticated instruments to identify the line of sight for the corneal compensation of presbyopia. J Refract Surg. 2012
and is provided with AcufocusKamra Inlays. Mar;28(3):168-73.
11. Yilmaz OF, Bayraktar S, Agca A, Yilmaz B, McDonald MB, van de
Complications of Intracorneal Inlays Pol C Intracorneal inlay for the surgical correction of presbyopia. J
Cataract Refract Surg 2008; 34: 1921-27
Complications regarding the biocompatibility of the material 12. Mulet ME, Alio JL, Knorz MC. Hydrogel intracorneal inlays for the
used for the intracorneal lenses have been described and correction of hyperopia: outcomes and complications after 5 years
include corneal stromal opacity, haze variants, epithelial or of follow-up. Ophthalmology 2009; 116(8): 1455-66
extracellular matrix deposits, infiltration, and keratolysis15-17. 13. Verity SM, McCulley JP, Bowman RW, Cavanagh HD, Petroll WM.
Modifications of the material in order to be more Outcomes of PermaVisionintracorneal implants for the correction of
permeable of fluids and nutrients along with byproducts hyperopia. Am J Ophthalmology 2009; 147(6): 973-7.
of the metabolism of the tissue, along with alterations in 14. Bouzoukis D., Kymionis G., Limnopoulou A., Kounis G., Pallikaris I.
postoperative medical treatment of the patients to include Femtosecond laser-assisted corneal pocket creation using a mask for
steroids and occasionally cyclosporine, have assisted in inlay implantation. J Refract Surg 2011, 20 (10).
decreasing the appearance of such adverse events and 15. Barraquer JI. Modification of refraction by means of intracorneal
in increasing the tolerance and stability of the outcomes. inclusions.IntOphthalmolClin. 1966;6:53–78.
Additionally, the development of the femtosecond lasers 16. Werblin TP, Patel AS, Barraquer JI. Initial human experience with
for the creation of the corneal tunnel has increased the Permalens myopic hydrogel intracorneal lens implants. Refract
predictability, speed and safety of the procedure. The inlays Corneal Surg. 1992;8:23–26.
are intolerant to de-centration and need to be re-centered 17. Alio´ JL, Mulet ME, Zapata LF, et al. Intracorneal inlay complicated
if they move. If the patient has constant glare and optical by intrastromal epithelial opacification. Arch Ophthalmol.
phenomenons, the inlay can be easily removed by opening 2004;122:1441–1446.
the pocket.
D-8, Vikas Puri, New Delhi – 110018
Conclusions Phone No’s: 011-28537777, 45623722
E-Mail: [email protected]
Modern Corneal Inlays demonstrate good efficacy of gain in
unaided near vision with minimal compromise on unaided Required
distant vision. This minimally invasive and reversible
procedure demonstrates good safety and maintenance of Ø Ophthalmologist (MD/MS/DO/DNS) (Full Time)
corneal structural health. However, new technology merits
further long term studies. Specialised in Ant. Segment Diagnosis + OPD
Managements. Also trained in Cataract Surgery
References (Phaco/SICS)

1. Kymionis GD, Bouzoukis DI, Pallikaris IG. Corneal inlays: A surgical Ø Specialist in Retina/Squint/Glaucoma/Cornea/
correction of presbyopia. J Cat RefrSurg Today Europe 2007; 3 48-
50. Oculoplasty – on Full Time/ Full Time.
Apply stating expertise and experience.
2. Barraquer J. QueratoplaticaRefractiva. Estudios e informaciones.
Oftalnologicas. 1949; 2: 10. Remuneration

3. Choyce P. The present status of intracorneal implants.J Cataract Commensurate with qualification &
Ophthalmol.1968; 3: 295. experience, negotiable.

4. Dohlman C, Refojo M, Rose J. Synthetic polymers in corneal surgery: Post your CV to [email protected]. or
glyceryl methacrylate. Arch. Ophthalmol. 1967; 177: 52-58. [email protected] with in 15 days. You
may also contact Mr. Mohit Arora @ 9871789999.
5. KlyceS, Dingeldein S, Bonanno J, et al. Hydrogel implants: evaluation
of first human trial. Invest. Ophthalmol Vis Sci Suppl. 1988; 29:393.

6. Seyeddain O, Riha W, Hohensinn M, et al. Refractive surgical
correction of presbyopia with the acufocus small aperture corneal
inlay: two-year follow up. J Refract Surg. 2010; 26: 1-9.

7. Yilmaz O, Bayraktar S, Agca A, et al. Intracorneal inlay for the
surgical correction of presbyopia. J Cataract Refract Surg. 2008; 34:
1921-27.

8. Sharma G, Porter T, Holliday K, et al. Sustainability and
biocompatibility of the Presby-Lens corneal inlay for the correction
of presbyopia. ARVO. 2010; 51: 813.

9. Slade St. Early results using the presbylens corneal inlay to improve
near and intermediate vision in emmetropicpresbyopes. Paper
presented at the ESCRS annual meeting. September 2010, Paris.

10. Bouzoukis DI, Kymionis GD, Panagopoulou SI, Diakonis VF,
Pallikaris AI, Limnopoulou AN, Portaliou DM, Pallikaris IG.Visual
outcomes and safety of a small diameter intrastromal refractive inlay

www. dosonline.org l 33

RefracRtievfreactSivue Srugregerryy

Aspheric IOLs -Facts & J.S. Bhalla
Myth
MS, DNB

J.S. Bhalla MS, DNB, Ankur Singh MS
Deen Dayal Upadhyay Hospital, New Delhi

In the current age of refractive cataract surgery, we measure an optical device (lens, mirror, etc.) that occurs due to
the quality of vision in addition to the quantity of vision. the increased refraction of light rays when they strike a
The patient’s image quality is as important as his Snellen lens or a reflection of light rays when they strike a mirror
acuity, particularly when we operate on patients with high near its edge, in comparison with those that strike nearer
expectations and high demands for their vision. the centre. It signifies a deviation of the device from the
Wavefront technology has been applied in cataract surgery norm, i.e., it results in an imperfection of the produced
to correct spherical aberration that is responsible for image. Spherical aberration is a rotationally symmetrical
decreased contrast sensitivity despite patient gaining 20/20 aberration that typically contributes considerably to higher-
vision postoperatively. The obvious goal of wavefront order wavefront errors and, depending upon lens power,
technology is to correct both lower order aberrations can induce either positive or negative aberration (Figure 1).
(LOAs) and higher order aberrations (HOAs) in an attempt Positive spherical aberration occurs when the peripheral
to achieve an ideal correction that produces ‘super vision.’ rays of light are refracted more than the central rays (plus
To this end, wavefront-guided refractive surgery, aberration- lenses) (Figure 2) while negative spherical aberration
correcting intraocular lenses, adaptive spectacle lens optics occurs when peripheral rays are refracted less (either less
and aberration-controlling contact lenses all represent positive or more negative) than the central rays (minus
attempts to provide patients with higher quality vision. In lenses) (Figure 3).
the last few years the clinical use of aspheric intraocular We know, for example, that the cornea induces
lens (IOLs) has grown dramatically. Understanding the approximately +0.27 units of spherical aberration to the
concepts behind these new IOL designs is instrumental to wavefront error, which is fairly constant throughout life
their effective use1. unless any refractive surgical interventions occur. Other
Aberration Descriptions and Definitions factors which influence spherical aberration include
Spherical aberration (SA) is an optical effect observed in pupil size (larger pupils increase spherical aberration),
accommodation (spherical aberration becomes negative
Figure 1 with active accommodation) and the application of different
contact lenses (induces negative spherical aberration).
The total higher-order aberrations of the phakic eye are
composed of aberrations arising from the anterior corneal
surface, the posterior corneal surface, the crystalline lens
and the retina. In the aphakic eye, however, 98.2 percent
of the aberrations arise from the anterior corneal surface.
As this discussion is about pseudophakia, then necessarily
the corneal aberrations are of importance, and for our
purposes, can be thought of being representative of the
whole aphakic eye.

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Figure 2 of visual performance. It can also enable individualized
comparisons to patients who demonstrate higher quality
Figure 3 vision. The PSF defines how a single object is imaged by
the optical system and provides a means to display how
Two categories of aberrations commonly are used to describe various aberrations affect a point of light, and therefore
vision errors, LOAs consist primarily of near sightedness and demonstrates the fundamental quality of a patient’s vision.
farsightedness (defocus), as well as astigmatism. They make When evaluating routine refractive errors with aberrometry,
up about 85 percent of all aberrations in an eye. HOAs uncorrected LOAs typically mask the presence of HOAs,
comprise many varieties of aberrations. Some of them have which are relatively small in magnitude.
names such as coma, trefoil and spherical aberration, but Measuring Aberrations
many more of them are identified only by mathematical Various devices have been developed to measure
expressions (Zernike polynomials). They make up about HOAs. One of the more common methods of aberration
15 percent of the total number of aberrations in an eye measurement uses Shack-Hartmann wavefront technology,
(Figure 4). which was originally designed for astronomical studies
The shape of a wavefront is typically described by a and was later applied to measuring ocular aberrations.
complex series of mathematical functions called Zernike Aberration measuring devices such as, i Trace Ray Tracing,
polynomials. These polynomials have varying radial orders Shack-Hartmann Aberrometer, Tscherning Aberrometer,
and meridional frequencies and can be demonstrated as Nidek OPD-Scan Aberrometer and Emory Vision Inter
different wavefront error maps. Another way to describe Wave Aberrometer have improved our ability to measure,
the wavefront shape uses a single number to describe the detect and understand the influence and effect that HOAs
amount the wavefront deviates from a plane wave. The have on the human ocular system.
amount of the deviation is called the root mean square What Impact Do Higher-Order Aberrations Have on
(RMS) error, As the RMS approaches zero, a perfect optical Vision Quality?
system would exist. The impact of higher-order aberrations on vision quality
Two other important measurements used in wavefront depends on various factors, including the underlying cause
aberrometry are modulation transfer function (MTF) and of the aberration. People with larger pupil sizes generally
point spread function (PSF). The MTF describes the ratio of may have more problems with vision symptoms caused
image contrast to object contrast as a function of the spatial by higher-order aberrations, particularly in low lighting
frequency of a sinusoidal grating across a patient’s range conditions when the pupil opens even wider. Other causes
are as scarring of the eye’s surface (cornea) or cataracts that
cloud the eye’s natural lens.
What Symptoms are Associated with Higher-Order
Aberrations?
An eye usually has several different higher-order aberrations
interacting together. Therefore, a correlation between a
particular higher-order aberration and a specific symptom
cannot easily be drawn. Nevertheless, higher-order
aberrations are generally associated with double vision,
blurriness, ghosts, haloes, starbursts, loss of contrast and
poor night vision.
For cataract patients, it is possible to measure the corneal
SAs using corneal topography preoperatively and then use
this data to manipulate the outcome of cataract surgery by
implantation of aspheric intraocular lenses, with the goal
of achieving an optimum SA for the eye and maximum
contrast sensitivity both of which indicate the overall
quality of the retinal image2.
Can Higher-Order Aberrations be Corrected?
Quite a bit of attention is being focused on higher-
order aberrations these days because they finally can be
diagnosed by wavefront technology (aberrometry) and

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Figure 4: Classification of Aberrations Figure 5: Spherical lenses have a constant curvature, as they are derived
from spheres, which results in peripheral light rays being defocused.
because they recently have been identified as sometimes
serious side effects of refractive surgery. Aspheric lenses have a variable curvature, but the lens power is constant
At present, various forms of adaptive optics have been at all points, resulting in equal focus of all light rays.
or are being developed to custom correct higher-order
aberrations. The aim of adaptive optics is to achieve the Figure 6: Comparison of various IOLs
type of vision correction that can make the shape of the
wavefront emerging in the plane of the pupil flatter by more positive spherical aberration than the cataracts they
offsetting its distortion. replaced (Figure 5).
Change of contrast senstivity with age By implanting an IOL with negative spherical aberration,
With age there is a loss of contrast sensitivity due to we can aim to offset the mild amount of positive spherical
degradation of the eye’s optical quality. Decrease in the aberration present in the normal cornea. This gives a total
modulation transfer function that occurs with age is partly of zero spherical aberration to the eye as a whole, as was
due to an increase of intraocular scattering and an increase the case at 25 years of age. By implanting an IOL with
of optical aberrations. Corneal astigmatism has been shown zero spherical aberration, we leave the eye with the mild
to change from with-the-rule to against-the rule with age, amount of positive spherical aberration that is present in
and an increase of prevalence of astigmatism with age has the normal cornea. This leaves the eye as a whole with a
been reported.
Change of Spherical Aberration with age
Negative spherical aberration of the crystalline lens shifts
toward positive values with age. The normal human cornea
has a mild amount of positive spherical aberration, which
is cancelled out by the mild amount of negative spherical
aberration present in the young crystalline lens2. while the
cornea’s level of mild positive spherical aberration stays
relatively constant throughout life, the crystalline lens
changes. The young crystalline lens has negative spherical
aberration, but it moves in the positive direction with age. In
middle age, the lens has zero aberration and as the cataract
develops it moves towards positive spherical aberration
The most dramatic change happens at the time of cataract
surgery, when a traditional IOL is implanted. This
dramatically increases the amount of positive spherical
aberration in the eye. Studies have shown that for age-
matched eyes, pseudophakic eyes have significantly

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Figure 7: Comparison of image quality of a photo (left) aberration and those with negative spherical aberration.
taken through a 22 D Aspheric IOL (SofPort AO) and The traditional IOLs with positive spherical aberration were
a 22 D traditional IOL (SofPort SE), though a camera the most commonly used lenses for pseudophakia. This has
changed in recent times as traditional IOLs gave a poorer
with a 5-mm pupil size (right). quality image than the aspheric IOLs in the vast majority
of patients.
Figure 8: Longitudal and Tranverse The zero aberration IOL that is now available is the Soft
Spherical Aberrations Port AO Advanced Optics silicone IOL (Bausch & Lomb,
Rochester, N.Y). This zero spherical aberration design is
small amount of spherical aberration, similar to a normal achieved via aspheric anterior and posterior surfaces of
45-year-old eye (Figure 5,6). the IOL.Negative aberration IOLs that are available are. (1)
Spherical lenses V/S Aspherical lenses Tecnis (Z9000, Z9002, Z9003) from AMO with S.A -0.27
Spherical lenses have a constant curvature on their surface, due to prolate anterior surface. (2) Acrysof IQ (SN60WF)
much in the same way that a sphere has a constant from Alcon Labs with S.A of -0.20 due to prolate posterior
curvature. However, the power of the lens at different points surface (Figure 7,8).
is variable, resulting in relative defocus of more peripheral We know from our experiences with corneal-based
light rays. Due to this constant curvature, these lenses are refractive surgery that there is far more to vision than
easier to make; however, their optics are worse. A perfectly Snellen acuities. Contrast sensitivity is an important
aspheric lens has a variable curvature but a constant power determinant of the quality of vision, and the more spherical
even at the periphery of the lens. This results in the same aberration that the eye has, the poorer the quality of vision
focus of all light rays, both central and peripheral resulting is. Studies have shown an improvement in simulated
in a sharper, higher-quality image. These lenses are more driving reaction time in patients with the Tecnis aspheric
difficult to make, but their optics are better. IOL3,4,5,6. Perhaps the best example of the difference among
Classifications of IOLS image qualities between spherical and aspheric lenses is
We can classify IOLs as either spherical or aspheric. Spherical obtained by taking a photograph of the U.S. Air Force test
IOLs have positive spherical aberration. The aspheric targets as seen through actual IOLs. When we compare the
category is subdivided into lenses with zero spherical image quality of the photographs, the improvement with an
aspheric IOL compared to an IOL that has spherical optics
but is otherwise identical (same power, same material,
same design, same manufacturer) is dramatic .7-10
Relationship of Depth of Field to Image Quality
With other factors such as pupil size, ambient lighting
and other aberrations kept constant, the effect of spherical
aberration on depth of field is inversely related to the
image quality of the eye. With less spherical aberration, the
image quality is better, but the depth of field is decreased.
Similarly, with more spherical aberration, the image quality
suffers, but the depth of field is increased (Figure 9)11.
Which IOL for Which Patient?
With three distinct classes of IOLs, which IOLdo we choose
for which patient? To properly match the IOL to the patient,
the questions that we should ask are
• What is the patient’s mesopic or scotopic pupil size?
Since the peripheral light rays are the ones that are

most affected by spherical aberration, if the patient has
small pupils at all times, he is unlikely to notice the
difference between an aspheric IOL and a traditional
IOL.
• What are the patient’s requirements for vision?
Patients who are active, still working, still driving at

38 l DOS Times - Vol. 19, No. 7 January, 2014

Refractive Surgery

night and are more demanding are more likely to notice Figure 10
the difference between aspheric and traditional IOLs.
Patients who spend a considerable amount of time at a How is the capsular support and what is the
fixed focal point, such as professional drivers watching likelihood of IOL decentration?
the road, would benefit from the best possible image The negative spherical aberration aspheric IOLs require
quality, even if it means a decreased depth of field. very good centration with respect to the visual axis of the
• How hyperopic is the patient? eye. Decentration of these IOLs results in a significant
The amount of spherical aberration increases with decrease in their performance and can even induce higher-
dioptric power in traditional IOLs. Therefore, the order aberrations such as coma.In case of loose zonules,
patients who need a +28 D IOL will have significantly creation of irregular capsulorhexis or eyes likely to undergo
more induced spherical aberration than those who significant capsule contraction, the centration of the IOL is
need a +14 D IOL. variable.These eyes would do well with a zero aberration
• Has the patient had previous corneal refractive IOL because it is relatively immune to decentration.
surgery? Can Patients Tell the Difference?
A patient with a history of prior myopic refractive In reality, the difference made by addressing asphericity is
surgery is likely to have flattening of the cornea usually very small compared to correcting spherical error
with a resultant increase in the corneal positive and astigmatism. Under low-contrast conditions, such as
spherical aberration. In this case, implanting an IOL driving at dusk, a patient with large pupils would be more
with negative spherical aberration will help to offset likely to notice the difference but the average cataract
this change and will result in better visual quality. A patient doesn’t have enormous mesopic pupils, but a
patient with a history of prior hyperopic refractive patient with an older style lens and a Plano prescription
surgery is likely to have steepening of the cornea with will be happier than a patient with an aspheric lens who is
a resultant decrease in the corneal spherical aberration, 1 D hyperopic or still has a diopter of astigmatism.
often to the point of negative spherical aberration. The most useful residual amount of asphericity to target
By implanting a traditional IOL that induces positive may depend on the full spectrum of corneal higher order
spherical aberration, we can help to balance out this aberrations, not just on corneal spherical aberration alone.
change and give better visual quality. This is one of the This is because of the way spherical aberration interacts
rare situations where a traditional IOL will outperform with other higher-order aberrations sometimes dampening
an aspheric one (Figure 10). them and also has effects on residual defocus, as well as
chromatic aberration.
Figure 9: When we compare the three classes of IOLs, we see Imprecision of Surgery
that the best image quality comes with the least amount of splay at Whether surgery is precise enough to avoid offsetting the
potential benefit of an aspheric IOL is also an issue. “We’re
the focal point; however, this lessens the depth of field. not at a point yet in cataract surgery that we can predict a
refractive outcome with absolute certainty”. We can’t tell
corneal aberrations or creating a model predicting the exact
effective position of the IOL. Furthermore, the capsular
bag can contract as part of the healing process, shifting

www. dosonline.org l 39

Refractive Surgery

Table 1: Different IOLs for different SA

Corneal SA Lens Implanted
-0.15 to +0.15 mm AMO Clariflex, B&L SofPort AO, or B&L Akreos AO
+0.16 to +0.33 mm Alcon IQ (SN60WF)
>+0.33 mm AMO Tecnis (Z9002, ZA9003 and ZCB00)
>-0.15 mm Standard intraocular lens

Figure 11: Performance of aspheric and traditional on the Zernike tree. As is better to have a patient with no
IOLs at various degree of defocus residual astigmatism than one who has no spherical and
other higher-order aberrations.
the axial position or centration of the lens. And being With the knowledge gained about advantages & limitations
centered in the bag may not be the same as being centered of Aspheric IOLs, we can have 4 different strategies to have
in the line of sight. In fact, there could be some advantage optimum visual outcomes.
to leave a little bit of spherical aberration to offset other Strategy 1: Do Not Use Aspheric IOLs
refractive errors that may occur as a result of the surgery. There have been a small number of studies which have
From a theoretical viewpoint, IOL decentration could limit, failed to demonstrate any perceived improvement in
cancel, or turn into disadvantages the benefits of aspheric vision with the use of aspheric IOLs13-15. However, these
IOLs. For example, the advantages of asphericity are lost reports had some inherent errors e.g. in many, the corneal
when IOL decentration is greater than 0.5 mm. Holladay spherical aberration is not measured. Similarly, many do
et al.report that optical quality measurements provide not report the pupil size. Another criticism is that patients
evidence that if an aspheric IOL were centered within 0.4 are assessed with subjective tests, such as the visual fields
mm and tilted fewer than 7 degrees, it would exceed the (VF). These tests are not as sensitive as contrast sensitivity
optical performance of a conventional spherical IOLt. testing and fail to show any improvement. Other factors
Another point is that best-corrected eyes with spherical IOLs that need to be studied are ocular dominance. No benefit
should perform better at near tasks than best corrected eyes were observed in patients with small mesopic pupils. A
with aspheric IOLs. Marcos et al. found that the tolerance small or contracted anterior capsulotomy can also negate
to defocus was significantly higher with spherical IOLs than the effects of an aspheric lens. Finally, as will be shown,
with aspheric IOLs, it was necessary to add 1.5 diopters there is an interaction between spherical aberration and
(D) with the spherical IOL and 1.1 D with the aspheric IOL residual refractive error. If this is not controlled, then the
to make the 20/20 line illegible on simulation. Recently, visual outcome will be less than ideal. Standard IOLs are of
Rocha et al11, concluded that the reduction in spherical more beneficial in patients undergoing hyperopic corneal
aberration after aspheric IOL implantation may degrade refractive surgery.
distance-corrected near visual acuity and intermediate visual Strategy 2: Same Aspheric for all Patients
acuity. They point out that residual spherical aberration can This approach certainly has some evidence to support it.
improve depth of focus and that the tolerance to defocus The main criticism of the “one lens for all patients” strategy
seems to be higher in eyes with a spherical IOL than in eyes is that it is akin to using a single-powered IOL in all cases
with an aspheric IOL12. of aphakia, irrespective of the parameters of the eye being
Either go for perfection or forget it. Preserving corneal implanted. This is a good first step, but experience shows
spherical aberration has the added advantage of making the that selecting the appropriate power of IOL provides
eyes more tolerant of defocus, without spherical aberration, superior uncorrected vision. Similarly, it should not be a
the quality of vision drops off much faster if one doesn’t hit huge leap of faith to accept that selecting an appropriate
refractive target exactly (Figure 11). aspheric correction should provide the best functional
Conquer Zernike’s lower orders first. Indeed, whichever vision.
aspheric IOL is chosen, the surgeon’s accuracy in hitting the Strategy 3: Target Aspheric Correction
refractive target is one of the most important determinants Although the average corneal SA for the population is +0.27
of refractive success. It is more important to nail the lower- µm, the standard deviation is large and approaches 0.10
order aberrations than it is to go after higher-order branches µm, or one-third of the value. Therefore it is recommended
to measure the patient’s corneal SA and using an aspheric
IOL to target a specific value that approaches 0.10 µm
by using the protocol in Table 1. After corneal refractive
surgery, some generalizations can be made if one cannot

40 l DOS Times - Vol. 19, No. 7 January, 2014

Refractive Surgery

directly measure the SA. Myopic laser ablation tends to postop refraction of plano is chosen. If the predicted SA
increase the SA, so a high-negative SA lens, such as the is negative, then a hyperopic refraction of 0.25 D for each
Tecnis, is recommended. Conversely, hyperopic ablation 0.10 µm of SA is targeted. If there is a positive predicted
tends to decrease the SA, and possibly make it negative, SA, then a myopic refraction of 0.25 D for each 0.10 µm of
so a standard lens with positive SA should be considered. SA is targeted.
Unfortunately, since each lens design comes in only one SA Utilizing this approach of choosing a lens material with the
power, this targeting approach has limited success. If one least amount of chromatic aberration, and a lens design that
is to use a single lens design, then the following strategy corrects for spherical aberration, with a defocus adjustment
has merit. to neutralize the SA, would seem to be the best strategy
Strategy 4: Match Corneal SA and Refraction for for optimizing vision in cataract or refractive lens exchange
Optimization of Vision patients.
It has been known for a while that different optical Summary
aberrations interact to affect visual performance. However, Aspheric IOLs are must in young patients with distinctly
the nature of this interaction has been elusive. Wang et al16 larger mesopic and scotopic pupils, who work under low
simulated implantation of lenses with different amounts of contrast conditions like driving at night, and who have
SA and with different amounts of defocus. They found that undergone refractive lens exchange and after myopic
the maximum image quality depended on an interaction LASIK. They are not useful in 1) Senile miosis 2) Subjects
between the residual SA and the defocus. For plano defocus, with not large mesopic pupils 3) After hyperopic LASIK, 4)
a SA of -0.05 µm was found to be ideal; for myopia of -0.5 In very old patients whose macula doesn’t have enough
D, a SA of +0.20 µm; and for hyperopia of +0.5 D, a SA of ganglion cells to notice benefit of asphericity of in IOLS, 5)
-0.2 µm was found to give best image quality. Factors of tilt/decentration and Defocus should always be
Using adaptive optics to study the optimal spherical considered while implanting aspheric IOLs.
aberration for contrast sensitivity, researchers found that for Asphericity of the lens does not make a tremendous
an SA of 0.00 µm, maximum vision occurs at 0 defocus; difference for the average patient.
for positive values of SA, a negative defocus provides best Best thing is to do a clean surgery and really nail the LOA
vision; and for negative values of SA, a positive defocus like residual refractory error & astigmatism, then try to
was found to be the best. The basis is strategy that allows conquer HOA. In most cases, you should probably use an
for the interaction of the measured corneal SA (at 6 mm) aspheric lens, but the one you choose should depend on
and a targeted refraction postop so as to optimize vision. (1) Cornea’s SA (2) IOL’S SA (3) Cornea whether virgin or
In addition to spherical aberration, it is also possible to has been subjected to refractive corneal surgery (4). Target
correct for chromatic aberration. Chromatic aberration of residual refractory error & residual SA postoperatively.
impacts negatively on vision and in particular on contrast Throw the marketing nonsense out of the window and see
sensitivity. The chromatic aberration of a material can be what works best for your patients. IOL companies should
expressed in its Abbe number; the higher the number, manufacture different combination of dioptric powers with
the lower the chromatic aberration and the greater the different values of asphericity.
optical quality. It has been shown that the AMO acrylic References
hydrophobic material has the least amount of chromatic
aberration of currently used IOL materials. 1. Holladay JT, Piers PA, Koranyi G, et al. A New Intraocular Lens
It has been found that a lens which only corrects for Design to Reduce Spherical Aberration Of Pseudophakic Eyes. J
spherical aberration improves contrast sensitivity by 20 Refract Surg. 2002;18:683-91.
percent over a standard lens; however, a lens that corrects
for both spherical aberration (to 0.00 µm) and chromatic 2. Guirao A, Tejedor J, Artal P. Corneal Aberrations Before And
aberration improves visual performance by 50 percent. After Small-Incision Cataract Surgery. Invest Ophthalmol Vis Sci.
Using the data previously presented to support the concept 2004;45:4312-19.
of targeting a specific postoperative refraction based on
the total spherical aberration of the eye so as to optimize 3. Wang L, Dai E, Koch D, Nathoo A. Optical Aberrations of The
vision, following protocol was decided: The corneal Human Anterior Cornea. J Cataract Refract Surg. 2003;29:1514-21.
spherical aberration at 6 mm diameter is measured preop.
Since the AMO Tecnis has a SA of -0.27 µm, and Acrysof 4. Kasper T1, Buhren J, Kohnen T. Visual Acuity, Contrast Sensitivity,
has SA of -0.20, this value is subtracted from the corneal and Higher-Order Aberrations. J Cataract Refract Surg. 2006;32:
SA. If the residual value is near 0.00 µm, then a target 2022-29.

5. Packer M, Fine IH, Hoffman RS, Piers PA. Improved Functional
Vision With A Modified Prolate Intraocular Lens. J Cataract Refract
Surg. 2004; 30:986–92.

6. Robert Monte´S-Mic, Teresa Ferrer-Blasco, Alejandro Cervin.
Analysis of The Possible Benefits of Aspheric Intraocular Lenses:

www. dosonline.org l 41

Refractive Surgery

Review of The Literature J Cataract Refract Surg. 2009; 35:172–81. Aberrations to Improve or Reduce Visual Performance. J Cataract
7. Wang L, Koch DD. Custom Optimization Of Intraocular Lens Refract Surg. 2003; 29:1487–95.
13. Beiko GHH. Aspheric IOLs matching based on Corneal And IOL
Asphericity. J Cataract Refract Surg. 2007; 33:1713–20. Wavefront. In: Chang DF, Ed, Mastering Refractive Iols; The Art And
8. Atchison DA. Design of Aspheric Intraocular Lenses. Ophthalmic Science. Thorofare, NJ, Slack, 2008; 278–281.
14. Beiko GHH. Personalized Correction of Spherical Aberration In
Physiol Opt. 1991; 11:137–46. Cataract Surgery. J Cataract Refract Surg. 2007; 33:1455–1460 21.
9. Altmann GE, Nichamin LD, Lane SS, Pepose JS. Optical Performance 15. Rocha KM, Soriano ES, Chamon W, Chalita MR, Nose´ W. Spherical
Aberration And Depth of Focus in Eyes Implanted with Aspheric
of 3 Intraocular Lens Designs In The Presence of Decentration. J and Spherical Intraocular Lenses; A Prospective Randomized Study.
Cataract Refract Surg. 2005; 31:574–85. Ophthalmology 2007; 114:2050–54.
10. Dietze HH, Cox MJ. Limitations of Correcting Spherical Aberration 16. AK Schuster et al. Impact on Vision of Aspheric to Spherical
With Aspheric Intraocular Lenses. J Refract. 2005; 21:541–46. Monofocal Intraocular Lenses in Cataract Surgery Ophthalmology
11. Wang L, Koch DD. Effect Of Decentration of Wavefront-Corrected Nov 2013,120(11);2166-75.
Intraocular Lenses On The Higher-Order Aberrations of The Eye.
Arch Ophthalmol. 2005; 123:1226–30.
12. Applegate RA, Marsack JD, Ramos R, Sarver EJ. Interaction Between

42 l DOS Times - Vol. 19, No. 7 January, 2014

Topography for the DiaDginagonsotsitcicss
Refractive Surgeon
Rohit Shetty
Rohit Shetty DNB, FRCS, Vishal Arora MD DNB FRCS
Narayana Nethralaya, Bangalore, Karnataka

Corneal topography is used to diagnose, monitor that the colours of different maps from even a same cornea
progression of various corneal pathologies, and aid cannot be compared directly as they may have different
in the preoperative evaluation for patients undergoing steps and the meanings of colours are lost.
refractive surgery. Topography evaluation can be done Axial curvature map or sagittal curvature map is the most
using devices based on the following principles: commonly used map. It is helpful in evaluating the overall
1. Placido Disc shape of the cornea. The biggest advantage of this map is
2. Slit scanning that the pattern diagnosis of a map can be done and a map
3. Scheimpflug imaging can be classified into normal or abnormal (Figure 1).
4. Optical coherence tomography Tangential curvature map or instantaneous map or
The various principles and respective platforms are meridional curvature maps are more sensitive in detecting
discussed below. local curvature change, hence can be useful in detecting
Computer-assisted videokeratoscopy/placido disc early changes, which might have been missed by the axial
based corneal topography map. It is more accurate than the axial map in corneal
Since the advent of elevation based topographer the placido periphery.
based topographers have lost favor, but still the commonest One must keep in mind to rule out keratoconus or other
topographers used in clinical practice are based on placido ectatic disease before undertaking the patient for refractive
disk principles. The instrument consists of either a placido surgery. For diagnosis of keratoconus, the Rabinowitz/
disk-type nose cone or a large placido disc consisting of
dark and light rings of different number and sometimes Figure 1: Classification of various patterns on axial map of
even colours. placido based topography. Top A, round; B, oval; C, superior
Before interpreting the data one must look at the output steepening; D, inferior steepening; E, irregular; F, symmetric
screen, warmer colours (reds, oranges) on the map represent
steeper cornea with higher keratometric dioptric power, bow tie; G, symmetric bow tie with skewed radial axes; H,
the cooler colours (violets and blues) represent flatter asymmetric bow tie with inferior steepening (AB/IS); I,
cornea with lower dioptric power and greens and yellows asymmetric bow tie with superior steepening; J, asymmetric
represent colours found in normal cornea. One can use
an absolute scale or standardized scale for interpretation, bow tie with skewed radial axes (AB/SRAX)
having fixed dioptric increment for colour scales and can
be used for comparing two maps, but is less sensitive.
Normalized maps have different colour scales assigned to
each map. Advantage is that it is more sensitive and can
even label normal cornea as keratoconic. Disadvantage is

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Diagnostics

Figure 2: Normal Orbscan quad map Figure 3: OrbscanIIz of keratoconus patient Showing
abnormal parameters with inferior steepening with
Mc Donnel1 diagnostic criteria consists of two topography skewing of steep axis, posterior BFS > 55, posterior
derived indices, which are as follows; central K-value > Diff. > 0.050 mm, Anterior diff >0.030, 3 mm zone
47.20 D and Inferior-Superior asymmetry (I-S value) > 1.4 irregularity >2 D, 5 mm zone irregularity > 3 D,
D. Rabinowitz/Rasheed’s described KISA% to diagnose Minimum pachy<470 µm.
keratoconus2. KISA% index is usually applied to the axial
map. It uses four indices on the topography. ablation of 12-15µm per diopter, total tissue burn
KISA% = [(K) × (I-S) × (AST) × (SRAX) × 100]/300 would be in the range of 60 to 75 µm. Considering
K-value here is central keratomertic value in access of 47.2 flap of 120µm for manual keratome, one can expect
D i.e., K-4 7.2. If value is less then or 47.2, it is replaced by a residual bed thickness (RBT) of 300 to 285µm.
1. I-S or inferior-superior asymmetry, AST calculated from Refractive surgeons vary in their opinion on adequate
(Sim K1-SimK2, SRAX is calculated from 180-the angle RBT but we prefer to keep it >300 µm for our patients.
between two steep axis above and below the horizontal 4. Keratometric Map: Gives the keratometric values for
meridian (smaller of the two angles). To amplify any anterior cornea.
abnormality, the value 1 was substituted in the equation One must look for the Red Flags (Figure 3) on Orbscan
whenever a calculated index has a value of less than 1. (Roush criterion)3,4
Slit Scanning elevation based topography 1. A thinnest point of < 470 µm on pachymetry
OrbscanIIz is a three-dimensional slit-scanning topography 2. A difference of > 100 µm from the thinnest point to
system used for analysis of the corneal anterior and the values of the 7 mm Optic Zone implies a steep
posterior surfaces as well as pachymetry. It uses a slit- gradient of thinning from mid-periphery to the thinnest
scanning system to measure 18,000 data points and a point.
Placido-based system to make necessary adjustments to 3. The thinnest point on the cornea should correspond
produce topography data. with the highest point of elevation of the posterior
A typical Orbscan Output is a quad map (Figure 2) corneal surface. On posterior elevations map a
1. Anterior Float: Elevation map of the anterior cornea, posterior high point > 50 µm above best fit Sphere
(BFS). BFS power greater than 55 D on the posterior
one must look for hot spots and irregularities on the profile.
anterior cornea. 4. Relative difference > 100 µm between the highest
2. Posterior float: It is important as Placido based systems and lowest point on the posterior elevation map.
cannot pick up early signs of ectasia, which starts from Power map Keratometric mean power map > 46 D.
the posterior float. One must look for hot spots and see Bow–Tie pattern or lazy C on the axial power map is
if it is coinciding with elevated anterior float. suspect when the astigmatism shifts > 20 degree from
3. Thickness map: Adequate thickness for LASIK depends a straight line.
on refractive error to be treated. For example a patient 5. A change within the central 3 mm optic zone of the
with -5 DS refractive error with thickness of 480 µm cornea of more than 3 D from superior to inferior
(No other warning signs) for LASIK. Assuming tissue can be correlated to the presence of vertical coma
(commonest aberration seen in keratoconus)

44 l DOS Times - Vol. 19, No. 7 January, 2014

Diagnostics

Figure 4: Pentacam refractive map Scheimpflug derived corneal thickness maps identify the
location and magnitude of the thinnest point on the cornea.
Figure 5: Pentacam BAD display of keratoconus patient In addition to measuring and locating the true thinnest point,
showing abnormal CTSP, PTI and D (> 2.60) values with a full thickness map allows one to look at the pachymetric
significant difference on both anterior and posterior elevation progression or the rate of change in corneal thickness. It
6. Composite integrated information which includes also gives information about posterior cornea, which is an
highest point on the posterior elevation coincides earlier indicator of ectatic change or ectasia susceptibility
with the highest point on the anterior elevation, the and when combined with full pachymetric data serves as a
thinnest point on pachymetry, and the point of steepest more sensitive screening tool then anterior topography and
curvature on the power map. ultrasound pachymetry combined5.
In addition to that Efkarpides criteria say that ratio of the Pentacam has a comprehensive refractive screening display
radii of the anterior BFS and posterior BFS of the cornea [Belin/ Ambrosio Enhanced Ectasia Display III– (BAD III)],
should be more than 1.21.Astigmatic discrepancy of > 1.5 which combines nine different tomographic parameters in
D in the 3 mm zone and a discrepancy of > 2 D in the a unified screening tool. An abnormal final reading, which
5mm zone should be an alert sign. is colour coded, indicates suspicious cornea (Figure 5). It
can also differentiate between keratoconus and pellucid
Scheimpflug imaging marginal degeneration which may mimic the former.
The Pentacam Standard (Figure 4) uses a rotating Scheimpflug An elevation of 12-15 µ on anterior surface and 18-22 µ
camera (180 degrees) to provide a 3-dimensional scan of on posterior surface should raise a suspicion of abnormal
the anterior segment ofthe eye. A monochromatic slit-light cornea (Figure 6).
source (diode-emitting bluelight at 475 nm) rotates around This added information improves the ability of the refractive
the optical axes of the eye. Within 2 seconds, 25 slit images surgeon to screen patients for occult ectatic disease or to
of the anterior segment are captured. Each slit image identify patients potentially at higher risk for post LASIK
possesses 500 true elevation points, and 25,000 points are ectasia.
obtained. For each slit image, mathematic software is used Sirius combines Scheimpflug camera and a small-angle
to detect edges, including the epithelium and endothelium Placido disk topographer with 22 rings. A full scanning
of the cornea. Finally, a 3-dimensional mathematic image acquires a series of 25 Scheimpflug images (meridians) and
of the anterior segment is generated. 1 Placido top-view image. The Placido image provides ring
edges, and height, slope, and curvature data are obtained by
thearc-step method with conic curves. Scheimpflug images
showed the profiles of anterior cornea, posterior cornea,
anterior lens, and iris. The data for the anterior surface are
finally determined by merging the Placido image and the
Scheimpflug images using a proprietary method. However,

Figure 6: Pentacam four map display of left eye of
keratoconus patient with inferior steepening, anterior
elevation +26 (normal < 12-15), corresponding posterior
elevation of + 72 (normal < 17-22), and corresponding

thin pachymetry (453).

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Diagnostics

Figure 7: typical Galilei 4 map display showing, are made by the dual camera from opposite sides of the
Tangential curvature, Pachymetry map, Anterior and illuminated slit, and the data are averaged. Meanwhile,
the dual camera simultaneously tracks decentration due to
posterior elevation. eye movements. In addition to refractive indices (Figure 7),
it utilizes the concept of Best Fit toricasphere (BFTA) that
Figure 8: BFTA of keratoconus suspect conforms regularly to the cornea than a BFS6. True corneal
patient with abnormal AAI power is also given, which is calculated using ray tracing.
It also gives Keratoconus prediction index (KPI), which
other data of internal structures (posterior cornea, anterior is based on anterior surface measurements. It predicts
lens, and iris) are obtained solely from the Scheimpflug percentage probability of keratoconus. KPI 0-10% is normal,
images. 10-20% is borderline to suspicious, 20-30% suspicious to
Systems with a single Scheimpflug channel use a keratoconus >30% is highly suggestive of keratoconus or
mathematical equation to estimate compensation for an off- pellucid marginal degeneration.
center measurement; however, the only way to properly Detection of subclinical keratoconus is of prime importance
compensate for an off-center measurement is with Dual- in modern refractive surgery, the posterior asphericity
Scheimpflug technology. asymmetry index (AAI) on Galilei is a quantitative indicator
Galilei uses a monochromatic slit-light source (diode of the posterior surface asymmetry which was first described
emitting blue light at 470 nm) which combines dual by Arce in 20107. AAI is calculated by absolute summation
Scheimpflug cameras and a Placido disc to measure of maximum elevation and maximum depression in the 6
both anterior and posterior corneal surfaces. It requires mm zone on BFTA map. Smadja et al8 concluded the AAI
1 or 2 seconds to make a whole scan, which obtains with a cutoff value of 21.5 μm and the corneal volume
more than 122 000 points. During the rotating scan, the at 30.8 mm3, as the two most discriminant variables
Placido and Scheimpflug data of the corneal information among the parameters incorporated in the analysis for
are simultaneously obtained. The anterior corneal differentiating between normal corneas and those with
measurements are made by a proprietary method of formefruste keratoconus (Figure 8).
merging the 2 types of data. Two Scheimpflug slit images Optical Coherence Tomography (OCT)
The use of OCT technology to obtain a precise pachymetric
map of the cornea was first described by Li et al., in 20069.
We use RTvue-100 which is a Fourier domain OCT featuring
5 mm of depth resolution in tissue and high-magnification
imaging of the cornea within 0.04 seconds. It adopts a
super-luminescence diode as a low coherence light source,
which emits light with a 50-nm band width centered at 830
nm. A corneal-anterior module long lens adapter with low
magnification is added to the RTvue to image the anterior
segment. The corneal pachymetry protocol acquires 8
evenly spaced 6-mm radial lines oriented 22.5 degrees
from one another, consisting of 1024 A-scans per line in
0.31 seconds.
The OCT is a noncontact imaging modality that provides
a high resolution cross-sectional analysis of the corneal
thickness. A quantitative system of assessment has been in
which five OCT pachymetry (Figure 9) characteristics were
identified which showed high specificity and sensitivity.
1. Minimum-median. (Cut off value: 62.6 µm).
2. The I-S: The average thickness of the inferior (I) octant

minus that of the superior (S) octant (cut off value: 31.3
µm).
3. The IT-SN: The average thickness of the IT octant minus
that of the SN octant (cut off value: 48.2 µm).

46 l DOS Times - Vol. 19, No. 7 January, 2014

Diagnostics

Figure 9: OCT pachymetry map with, true net
power and various indices.

Figure 11: Pentacam with normal indices but
patient had poor biomechanics as measured on

Corvis-ST (Red Box, normal < 1.10)

Figure 10: Epithelial map of a keratoconus Summary
patient with epithelial hyperplasia at the base Topography is an excellent tool to screen out potentially
borderlines cases in refractive practice. Placido disc based
of the cone (left > Right) devices are very useful tool; however they do not show
any changes on the posterior surface of the cornea. Newer,
4. Minimum (cutoff value 491.6 µm). diagnostic devices like elevation based topographers and
5. Vertical location of the minimum. Locations superior OCT can help us to visualize the posterior surface of cornea
and can also give an accurate idea about the pachymetry of
to the corneal vertex had positive values and locations entire cornea. These newer modalities can help us diagnose
inferior to the vertex had negative values (cut off value: ectatic disease in preclinical stage, thus allowing an early
716 µm). treatment.
Epithelial thickness profile (Figure 10) maps using Fourier
domain OCT have been shown to be useful in detecting References
subtle epithelial changes, which have been to be a sign
of early keratoconus10. Apical epithelial thinning over the 1. Rabinowitz YS, McDonnell PJ. Computer-assisted corneal
apex of the cone in early ectasia can mask top ographic topography in keratoconus. Refract Corneal Surg 1989;5:400-8.
changes on anterior corneal surface.
Future Trends 2. Rabinowitz YS, Rasheed K. KISA% index: A quantitative
Good topography (Pachymetry) and meticulous surgery videokeratography algorithm embodying minimal topographic
doesn’t guarantee that patient will not develop post LASIK criteria for diagnosing keratoconus. J Cataract Refract Surg 1999;25:
ectasia. Unfortunately, we still lack clear cut guidelines to 1327-35.
label patients on topography as at risk or normal. Corneal
biomechanics, which is measure of elasticity and strength 3. Li X, Yang H, Rabinowitz YS. Keratoconus: Classification scheme
of cornea, coupled with careful analysis of topography can based on videokeratography and clinical signs. J Cataract Refract
be a better screening tool for screening patients undergoing Surg 2009;35: 1597-603.
LASIK. We have come across a number of patients who
have seemingly normal topography but poor biomechanics 4. Rousch C. Orbscan II Manual (Salt Lake City, Utha. Orbtek)
(Figure 11). We believe these patients are potential 5. Ambrosio R Jr, Caiado AL, Guerra FP, Lousada R, Roy AS, Luz A, et
candidates, who can develop ectasia after LASIK surgery
and hence, LASIK should not be done on these patients. al. Novel pachymetric parameters based on corneal tomography for
diagnosing keratoconus. J Refract Surg 2011;27:753‑8.
6. Gatinel D, Malet J, Hoang-Xuan T, Azar DT. Corneal elevation
topography: best fit sphere, elevation distance, asphericity, toricity,
and clinical implications. Cornea. 2011 May;30(5):508-15.
7. Arce C. Qualitative and quantitative analysis of aspheric symmetry
and Asymmetry on corneal surfaces. Poster presented at: the ASCRS
Symposium and Congress; April 9-14 2010.
8. Smadja D, Touboul D, Cohen A, et al. Detection of subclinical
keratoconus using an automated decision tree classification. Am J
Ophthalmol. 2013;156(2):237-246.
9. Li Y, Shekhar R, Huang D. Corneal pachymetry mapping with
high-speed optical coherence tomography. Ophthalmology
2006;113:792-9.
10. Li Y, Tang M, Zhang X, Salaroli CH, Ramos JL, Huang D. Pachymetric
mapping with Fourier-domain optical coherence tomography. J
Cataract Refract Surg 2010;36:826-31.

www. dosonline.org l 47

Prevention of Recurrence of Pterygium: S/C MiscMeilslcaelnlaenoeouuss
Mitomycin–CVsTopical Cyclosporine-A
Shakeen Singh
MBBS,MS, DOMS,

Shakeen Singh MBBS,MS, DOMS, Ripan Wassan MBBS, MS, B.S. Dhillon MBBS, MS
Sri Guru Ram Dass Hospital, Amritsar, Punjab

Pterygium (Pterygos in Greek: small wing) is a fibro- Method
vascular growth of actinically damaged conjunctiva This was a randomized clinical trial conducted on 120
encroaching upon the cornea within the interpalpebral eligible patients referred with a diagnosis of primary
fissure, more commonly on the nasal side. Pterygia can pterygium to a tertiary referral hospital at Vallah, Sri
vary from small, atrophic silent lesions to large, aggressive, Amritsar. The patients were divided into two groups and
rapidly growing fibro-vascular lesions that can distort the different treatment modalities were employed in each
corneal topography, and in advanced cases, can obscure group. Group I – (60 patients) Sub-Conjunctival 0.1ml of
the optical centre of the cornea. 0.015% Mitomycin C half an hour preoperatively followed
For pterygium,a wide range of etiology and treatment by simple excision of pterygium. Group II – (60 patients)
options have been proposed till date including dryness, Excision of the pterygium followed by topical cyclosporine-
air pollution, dust and wind1. Excessive exposure to the A 0.05% for 3 weeks.
ultraviolet sunlight which damages limbal stem cell barrier A comprehensive ophthalmic examination, including
seems to be the most important predisposing factor that best-corrected visual acuity testing, slit-lamp examination,
leads to subsequent conjunctivalization of the cornea2. Goldmann applanation tonometry, and fundus examination,
A number of treatment modalities have been employed for was carried out for all participants.
surgical treatment of pterygium including basic bare sclera In Group I: Patient was anesthetised with topical anaesthesia
excision. The rate of pterygium recurrence after a simple achieved with the instillation of proparacaine eye drops.
excision could be unacceptably high, between 30% and Inj. Mitomycin C 0.015% was prepared by diluting 2mg
89%3,4. and the rate after subsequent excisions may be commercially available injection of Mitomycin C with
even higher. 13cc distilled water taken in 20 cc syringe and 0.1cc
Various adjuvant therapies or surgical modifications have of this diluted solution was taken in insulin syringe and
been proposed for the prevention of a high incidence injected in belly of pterygium at limbus. Half an hour
of pterygium recurrence after simple excision. Studies later patient was prepared for surgery. Position was made,
conducted were by using adjunctive therapies like eye was cleaned with 5% betadine soaked swab. Belly
Mitomycin C and Cyclosporine A. Hamid et al, Ghoneim of pterygium was infiltrated with 1cc of 2% Xylocaine
et al5, have shown decrease in recurrence rate to 5.6% and with Adrenaline, thus making the body more prominent.
2.8% using preoperative subconjunctival mitomycin C in Pterygium was lifted gently with lim’s forcep at the limbus
the pterygium. Cyclosporine A 0.05 % eye drops has shown and dissected carefully from sclera underneath. The body
recurrence rate of 12.2% to 22.2% as shown by Ozleim et of the pterygium was excised parallel to limbus, 4mm from
al and Turan Vural et al6,7. The purpose of this study was the same, leaving 4mm bare sclera. Head of the pterygium
to compare two recent techniques used recently that is pre was removed from the cornea by superficial dissection with
operative subconjunctival Mitomycin C and post operative crescent parallel to the cornea. Polishing of corneal surface
topical cyclosporine A for the prevention of recurrence of was done. Thus a pterygium free cornea with 4mm bare
pterygium. sclera was achieved at the end of the operation.

www. dosonline.org l 51

Miscellaneous

IN Group II Routine antiseptic cleaning of the Lid eyeball No major intraoperative complication was found in
and surrounding area was done with povidone betadine both groups. Post operatively 2 patient presented with
iodine 5% solution. Proparacaine eye drops were used to excessive whitening of the sclera and in 2 we noticed
obtain topical anaesthesia. One cc of 2% Xylocaine with hypovascularity at the site of injection amongst group 1
Adrenaline was injected in the belly of the pterygium. The patients. No significant complication was noticed in group
mass was held at the Limbus and dissected from sclera II. Complication rate in group I accounting to 3.3% while
underneath with corneoscleral scissors. The belly was cut it was 0% in group II. On statistically analyzing the two
at 4 mm from the limbus. The head of the pterygium was groups we found the difference to be insignificant (p>
dissected from the cornea with help of crescent. Polishing 0.05%). The recurrence rate in group I was found to be
of corneal surface was done with crescent. The eye was 6.6 % while it was 16.6% in group II. On comparing the
patched with Antibiotic eye ointment after cleaning the recurrence rate between the two groups, it was found to
area. be significant. It was observed that younger the patient,
On first post operative day patients were started on topical higher was the incidence of recurrence. Of the 50 patients
antibiotic steroid combination four times daily, topical of 40 year or younger age, 12 (24%) developed recurrence.
lubricant six times daily, plain antibiotic ointment HS in Of the 70 patients of over 40 years of age only 2 (2.8%)
both the groups. Patients in group 2 were additionally developed recurrence which is highly significant (p <
started with cyclosporine 0.05% eye drops to be instilled 0.001). There was decrease in ‘with the rule’ astigmatism
at two times daily. postoperatively in both groups. The mean decrease in
Patients were regularly followed up at 1 week, 15 days, 1 cylindrical error was highly significant (p<0.001). No
month 3 months 6 months 9 months and 12 months post significant difference between the two groups. Power of
operatively to scrutinise any sign of complication or any horizontal curvature of cornea showed significant increase
recurrence. After surgery, growth of greater than 1mm was p(<0.05) within two groups due to reduction in traction
considered to be a recurrence. The complication rate and caused by the pterygium. No significant difference was
recurrence rate was compared between the 2 groups using observed between the groups. Power of vertical corneal
chi-square and Fisher exact tests. Intergroup changes for curvature did not show significant change post operatively.
continuous parametric variables were evaluated by the Visual acuity improved by one line in 90 (75%) cases, by
unpaired Student t test. For all measurements, a 2 - tailed two lines in 12 (10%) and no change was noticed in 18
test was used, and the statistical significance level was set (15%) of the cases. No patient showed decrease of visual
at P < .05. acuity.
Results Discussion
Pre-operatively all the parameters in 2 groups were found to The most effective therapy for pterygium is surgery. Bare
be statistically non-significant. The following observations sclera excision is still practiced widely around the world
were made during the study. as a basic and simple technique for pterygium removal but
Overall, 14 (11.6%) of the patients were in 21-30 years of has high recurrence rate. So adjunctive treatment with beta-
age group, 36 (30%) in 31-40 years age group, 28 (23.3%) irradiation or antimitotic agents such as mitomycin-C and
were in 41-50 years age group, 16 (13.3% 6 years) & 26 thiotepa were induced to reduce the rate of recurrence[8].
(21.6% 6 years) were in 51-60 years age group and of >61 The purpose of this study was to compare and evaluate
years respectively. Out of 120 cases, 68 (56.7%) were the efficacy of 2 surgical techniques that is pre operative
males and 52 (43.3%) were females. 70 (58.3%) cases had mitomycin C 0.015% followed by bare sclera surgery; and
pterygium on right side and 25 (41.7%) had pterygium on Bare Sclera surgery followed by post operative cyclosporine
left side. Fifty (83.3%) cases had unilateral presentation A 0.05% and to see the complications of each procedure
while it was bilateral in 10 (16.7%) cases. Pre-operatively, if any.
myopia was seen in 28 (46.6%) cases, hypermetropia Preoperative characteristics of eyes with pterygium among
in 26 (43.4%) cases and no spherical error in 6 (10%) two groups:
cases. A total of 53 (88.3%) cases showed ‘with the rule’ Age incidence: Out of 120 eyes studied, majority of the
astigmatism while 6 (5%) cases showed “against the rule” patients were between 3rd and 5th decade of life (21 to
astigmatism. No astigmatic error was seen in 8 (16.6%) 50 years of age). The youngest patient was 23 years of
cases pre-operatively. In group I 28 (46.6%) cases, in group and the oldest, 72 years. The mean age in group I was
II 40 (66.6%) had a visual acuity of 6/12 or better. The 41.40±11.38 years and in group II was 42.92±10.34. The
mean pretreatment power of horizontal corneal curvature age range of 23 to 73 years is due to the most active phase
was 41.68D ± 1.92D in group I and 41.76D ± 1.96D in of life, particularly in relation to the persons doing outdoor
group II. activities who are exposed to the effect of irradiation, such
as that of sunlight, dust or winds. The age incidence was

52 l DOS Times - Vol. 19, No. 7 January, 2014

Miscellaneous

consistent with the findings of Hilgers who have reported conducted by Hirst et al10, the average horizontal size
the highest incidence between the age of 20 and 49 years9. of pterygium was 3.1 mm (range 1.5 – 7mm) while in
Hirst et al have reported the mean age of 42.4 years another study conducted by Tan et al the horizontal size
(range 18.4 to 78.5 years) in their study population while of pterygium varied from 2 to 8 mm with a median size of
McCoombes et al have reported the average age of 45.1 4mm. This distribution was probably due to the fact that
years10,11. Rao et al have reported the mean age of 42.7+ this comprised a random study.
14.5 years in their study population. With the increase in the size of pterygium, both the
Sex incidence Duke elder observed that outdoor workers spherical and cylindrical refractive errors are seen to
are more affected than indoor workers, hence higher increase proportionately in most of the cases. Pterygia
prevalence among men12. In this study, males outnumbered appear to have a minimal affect on the central cornea
females. This was in consistence with the report of Waller until they exceed 45% of the corneal radius (or reach
and Adamis who reported higher prevalence among men within 3.2m of the visual axis). Once this critical size is
and greater risk of pterygium development in persons living reached, increasing degrees of astigmatism are induced18.
in outdoor environment13. In the study conducted by Tan However, this is not true in every case as the traction that
et al, there were a total 118 males (75%) and 39 females the pterygium causes, may not necessarily depend on its
(2.5%)14. McCarty et al reported 43.6% as an attributable size, since smaller sized pteygium may be in a father stage
risk of sunlight and pterygium15. He also reported that of cicatrization than a large sized one, which may be in
UV exposure (measured as latitude of residence, living its early stage of vascularisation. The astigmatism depends
environment, time spent outdoor and use of a hat) in upon the adhesions, attachment and contraction due to
the early years of life was found to be associated with fibrovascularised tissue of pterygium.
development of pterygium. Gazzard et al reported that a Refractive error: In the present study, myopia was equally
history of >5 hours/day of outdoor activity 10 years earlier distributed as hypermetropia in both the groups with total
was associated with almost twice the rate of those without prevalence of myopia in 56 cases (46.66%), hypermetropia
such a history whereas a history of > 5 hour/day of outdoor in 52 and no spherical error in 12 cases among 120 cases.
activity 5 years earlier was not significantly related (7.7% Predisposition is seen in relation to the astigmatism as most
and 11.1%, p=0.2) with pterygium16. of the cases present ‘with the rule’ astigmatism. This is so
Eye: There is no specific predilection for the involvement because of pooling of tear film at the leading edge of the
of a specific eye (right or left) and pterygium is seen in both pterygium and due to traction by the fibrovascularised
the eyes equally. In the present study, the right eye was tissue of pterygium resulting in the flattening of the
involved in 70 cases as compared to 50 cases in which the cornea in the horizontal meridian18,19. The study report
left eye was involved . In the study conducted by Hirst et al, was consistent with the study of Ozdemir and Cinal6 who
there were 93 pterygia in the right eye and 68 pterygia on reported 81.25% cases of ‘with the rule’ astigmatism at the
the left. While in another study conducted by McCoobes et preoperative period. Majority of the astigmatism seen in the
al, of the 258 cases right eye was involved in 138 cases as study was caused by the pterygium itself since it was mostly
compared to left eye in 123 cases. ‘with the rule’ whereas naturally occurring astigmatism can
Site Pterygium occurs more commonly on the nasal side. occur at any of the axis.
This may be due to greater exposure of this area to actinic On analyzing all the preoperative parameters between
damage and accumulation of dust particles in the anatomical the 2 groups statistically, the difference was found to be
pocket formed on the nasal side. Temporal location is insignificant.
uncommon because the bulbar conjunctiva lateral to Post–Operative Characteristics of Eyes with Pterygium
the cornea is situated just below the lacrimal gland and among two groups:
received the tears first have washing effect D’ombrain17. In Complications
our study, all pterygia occurred on the nasal side. In the Group I
study conducted by Hirst et al, the pterygium was nasal in In the present study, preoperative subconjunctival
155 eyes and temporal in 6 eyes10. In the study conducted Mitomycin C 0.015% followed by no serious complication
by Tan et al (1997), most (90%) of the pterygia were located was observed. Only 2 cases showed hypovascularity
nasally. and excessive whitening of the sclera at 9 month period
Laterality: In this study, there was unilateral involvement in of follow up. Minor early post operative complications
100 eyes and bilateral pterygium in 20 eyes (16%). These included persistent pain in 4 patients, photophobia in
figures correspond to those of McCoombes et al11, who 2 and foreign body sensation in 4 patients with watery
reported 19 bilateral pterygia among 222 eyes. discharge but all of them were asymptomatic by the end
Size: In our study, the average horizontal size was of 12 months. In the study conducted by Hamid et al the
approximately 2.25 mm (range 0.5 to 4 mm). In the study

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Miscellaneous

Complication rates after Pre-Operative Mitomycin-C Followed by bare Sclera Excision as Reported by Different Authors

Sl. No. Author Year Total Eyes Complication Rates Complications Follow up :mth

1 Donnerfield 2002 36 Zero Zero 24.4

2 Avisar et al 2005 27 Zero Zero 12

3 Ghoneim et al 2008 35 2.8% Sclera thinning 12

4 Hamid et al 2010 36 5.6% Whitening of sclera 12

5 Present Study 2012 60 3.3% Whitening of sclera 12
Hypovascularity

Recurrence rate following pre-operative Mitomycin C in bare Sclera Excision pf Pterygium as Studied by various
authors

Sr. No. Author Year Total Eyes Recurrence Rates Follow up period (months)

1 Donnerfield et al 2002 36 6% 24.4

2 Avisar et al 2005 27 3% 12

3 Ghoneim et al 2008 35 5.7% 12

4 Hamid et al 2010 36 4.3% 12

5 Present Study 2012 60 6.6% 12

complications reported were excessive whitening of the preoperative Mitomycin C in the pterygium, followed by
sclera at the injection site in one case with hypovascularity bare sclera excision. Donnenfield et al21 described the
in the same5. Avisar on a mean follow up of 15 months did recurrence rate of 6%, Avisar et al20 described recurrence
not report any complication20. Donnenfeld also reported of 3%, Ghoneim et al22 described recurrence of 5.7% while
only mild irritation and conjunctival swelling 28% of the Hamid et al5 showed recurrence of 4.3%. The present study
cases while subconjunctival haemorrhage in 22% of the showed recurrence of 6.6% in 12 month.
cases21. No serious complication was reported by him. Group II The present study showed a recurrence rate
Group II (Bare Sclera pterygium excision followed by of 16.6% on an average follow up of 60 cases for 12
topical cyclosporine eye drops for 3 months). months. Ecc Turan Vural7 showed the recurrence rate of
In the present study, 16 patients presented with persistent only 22.2% when the drops were instilled for six months
pain, 4 with photophobia, 10 with watery discharge and 20 post operatively. A similar study conducted by Ozleim[6]
each with irritation and foreign body sensation in the early showed a much lower rate of 12.9% post bare sclera
postoperative period. These symptoms decreased with the excision.
start of topical antibiotics and corticosteroids. By the end of Association of Age with Recurrence of Pterygium Age of
12 months, all the patients were asymptomatic. Ecc Turan the patient is strongly associated with the recurrence of
Vural et al7 and Ozleim et al6 also showed no significant pterygium regardless of which procedure was used for
complication in post operative period in the eyes treated its treatment. In the present study, only 2 patients with
with cyclosporine 0.05% eye drops post operatively. recurrence were older than 40 years of age while rest of 12
Patients complained of only slight burning on instillation patients were younger than 40 years (p<0.05). Zauberman
of the drops. reported 13.6 to 36.1% recurrence in pterygium especially
Recurrence rates in pterygium in younger age group. In the study conducted by Lewallen
Recurrence of pterygium is defined as an encroachment of S23, all the recurrences occurred in patients younger than
fibro vascular connective tissue 1mm across the limbus and 37 years of age. Rao et al24 too found their recurrence in
onto the cornea for any distance in the position of previous patients younger than 40 years of age. The presence of
pterygium after excision. increasing amount of lipoid degeneration with age which
Group I In the studies conducted on pterygium high acts as an inhibiting factor might explain in part the strong
recurrence rate was reported with bare sclera excision alone association we found between age and recurrence.
but the work done by few researchers using adjunctive Pterygium Recurrence Time In the present study, a total of
like mitomycin C markedly decreased the recurrence 14 recurrences were seen in 120 patients on a follow up
rate as shown in the following table. The workers used of 12 months. Hirst et alconducted a study to define the
amount of time necessary to follow patients after pterygium

54 l DOS Times - Vol. 19, No. 7 January, 2014

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Time of Recurrence of Pterygium as Reported by different authors

Sr. No. Author Total Eyes No. of Time of Recurrence Follow up period
Recurrences (months)
12
1 McCoombes et al 222 7 (3.2%) Average 4.3
(1993) (1.5-11) months Average 1 year
11
2 Chen et al (1995) 64 33 (51.5%) 3.7 to 4.8 months 5.2
23
3 Prabhasawat et al 46 (AMG) 20 5 (10.9%) 4.1±3.7 months Average 1 year
(1997) (primary closure) 9 (45%) 11.1±1.6 months
78 (CAG) 2 (2.6) 3.7±1.4 months 12

4 Ti et al (1997) 139 (primary) 29 (20.8%) 25 by 6 months
67 (recurrent) 20 (31.2%) 17 by 6 months

5 Present study 60( gp 1) 4(6.6%) 2 by 1st month and 2 by 3rd
(2012) 60 (gp 2) 10 (16.6%) month and
2 by 1st month
8 by 3th month

removal to identify a recurrence. Their observations remnant corneal opacity was seen in our study. Gazzard
showed an average time for the first occurrence of 123 et al, reported that late surgical treatment of pterygium is
days, with second and third recurrences recurring at associated with more frequent permanent corneal opacity,
earlier intervals, 97 and 67 days respectively. The trend for more complex and more residual astigmatism.
recurrences to happen more quickly with each subsequent Visual acuity
removal, regardless of the type of surgery involved, raises In our study, visual acuity improved in most of the patients
the possibility that there may be a host specific resistance due to decrease in refractive astigmatism and spherical
to re growth that surgical removal may destroy. error. There was improvement by 1 line in 90 cases, of 2
Keratometry and refractive astigmatism lines in 12 cases and of 3 lines in none of the cases. No
In most of the cases, in both of the groups, k1 was of lesser change in visual acuity was seen in 18 cases. In the study
value than K2 resulting in cases of with the rule astigmatism conducted by Seid and Bejiga, there was improvement
preoperatively. After pterygium surgery, k1 increased in of visual acuity in 24 cases and it remained the same in
most of the cases resulting in decrease in magnitude of eight cases out of total 32 cases27. Maheshwari reported
‘with the rule’ astigmatism or ‘no astigmatism.’ Cases of 1 or 2 line improvement in 15 eyes (41.67%) out of total
no astigmatism increased from 8 to 40 postoperatively. 36 eyes28. Noor reported an increase in visual acuity by 2
Vertical curvature (k2) remained the same in most of the lines post-operatively as visual acuity improved from 6/12
cases. It showed decrease in 14 cases and increase in 4 to 6/629. Our study findings were consistent with the studies
cases among 120 cases. done till date.
Maheshwari reported decrease in preoperative refractive Histopathological study of the excised mass was done.
cylinder from 4.60±2.0D to 2.20±2.04D (p<).00001) In the first group of mitomycin C, histopathological
after pterygium excision in study group of 72 eyes who study showed the absence of damage to the conjunctival
presented with primary pterygium with pre-operative epithelium on light microscopy, as previously reported
astigmatism of 2 D or more25. with topical application of mitomycin C30. Most important
Increase in horizontal curvature (k1) after pterygium was the notation of multiple foci of goblet cells. These
excision can be explained by decrease in corneal traction cells are often absent because of the toxic effect of topical
caused by pterygium resulting in decrease in with the rule mitomycin C application, and the presence of goblet cells
astigmatism. Increase in k2 in some cases can be explained strongly argues for the health of the epithelium overlying
as due to pressure of lids as a result of blepharospasm the areas of treatment. The findings were consistent with
postoperatively. Bedrossian studied the changes in the findings by Donnenfeld15 who conducted the similar
astigmatism following pterygium excision, and usually study using mitomycin C preoperatively followed by
noted an increase in the corneal curvature in the horizontal excision. Histopathological study on the second group did
meridian and a decrease in ‘with the rule’ astigmatism26. not show any significant change as compared to the normal
However, there was a poor correlation between changes histopathological study of the pterygium shown by other
in corneal curvature and refractive error. Four cases of workers.

www. dosonline.org l 55

Miscellaneous

References 16. Gazzard G, Saw SM, Frook M, et al. Pterygium in Indonesia:
Prevalence, severity and risk factor. Br J Ophthalmol. 2002; 86(12):
1. Sihota R, Tandon R. Diseases of the conjunctiva. Parson’s Diseases 1341-46
of the eye. 19th edn. Edinburg, London: Butterworth-Heinemann,
2003; p169-99 17. D’ombrain A. The surgical treatment of pterygium. Br J
Ophthalmol.1948; 32: 65-71.
2. Kamel S. Pterygium: its nature and a new line of treatment. Br J
Ophthalmol. 1946; Sept. 30:549-63. 18. Lindsay RG, Sullivan L. Pterygium induced conical astigmatism. Clin
Exp Ophthalmol. 2001; 84(4): 200-03.
3. Singh VP. A Survey of Ocular Morbidity in the general population,
Nagpur University of Nagpur (MS Thesis), 1990; 44-45. 19. Hochbaum DR, Moskovitz SF, Wirtschaffer JD. A quantitative
analysis of astigmatism induced by pterygium. Journal of
4. Khosla PK. Community Ophthalmology- an Indian Prospective. Biomechanics. 1977; 10: 73-75.
2ndedn.New Age International. 1992; p295
20. Avisar R, Shmuel B, Weinberg D. Preoperative Injection of
5. Hamid K, Mohammad ER, Daneshwar R. Preoperative Mitomycin C in Combined Pterygium and Cataract Surgery. Cornea.
Subpterygeal Injection Vs Intraoperative Mitomycin C for Pterygium 2005; May, 24(4):406-09.
Removal:Comparison of Results and Complications. Am J
Ophthalmol. 2010; 88 : 193-8. 21. Donnenfeld ED, Perry HD, Fromer S. Subconjunctival mitomycin C
as adjunctive therapy before pterygium excision. Ophthalmol. 2003;
6. Ozlem YT, Ayse BN, Ergun A. Topical Cyclosporine A in the 110: 1012–26.
Prevention of Pterygium Recurrence. Ophthalmologica. 2008; 222:
391–6. 22. Ghoneim EM, Ghny AA, Gab-Allah A, Preoperative subconjunctival
mitomycin C versus intraoperative topical application as an
7. Turan-Vural E, Torun-Vural A, Argun. The effect of topical 0.05% adjunctive treatment for surgical removal of primary pterygium. Mid
cyclosporine on recurrence following pterygium surgery. Clinical East Afr J Ophthalmol. 2011; 18(1):37-41.
Ophthalmol. 2011; 5: 881-5.
23. Lewallen S. A. Randomized trial of conjunctival autograft for
8. Prabhasawat P, Barton K, Burkett G, et al. Comparison of pterygium in the tropics. Ophthalmol. 1989; 96: 1612-14.
conjunctival autografts, amniotic membrane grafts, and primary
closure for pterygium excision. Ophthalmology, 1997; 104 (6): 974- 24. Rao SK, Lekha T, Mukesh BN. Conjunctival limbal autografts for
85. primary and recurrent pterygia: Technique and Results. Indian
Journal of Ophthalmol. 1998; 46: 203-09.
9. Hilgers JHC. Pterygium: its incidence, heredity and aetiology. Am J
Ophthalmol. 1960; 50: 635-43. 25. Maheshwari S. Effect of pterygium excision on pterygium induced
astigmatism. Indian J Ophthalmol. 2003; 51(2): 187-88.
10. Hirst LW, Sebban A, Chant U. Pterygium recurrence time.
Ophthalmology, 1994; 101: 755-8. 26. Bedrossian RH. The effects of pterygium surgery on refraction and
corneal curvature. Arch Ophthalmol. 1960; 64: 553-57.
11. McCoombes JA, Hirst LW, Isbell GP. Sliding conjunctival flap for the
treatment of primary pterygium. Ophthalmology, 1994; 101:169-73. 27. Seid A, Bejiga A. Free conjunctival autograft in the management
of advanced primary and recurrent pterygia. East Afr Med J. 2000;
12. McCarty CA, Fu CL, Taylor HR. Epidemiology of pterygium in 77(11):588-91.
Victoria, Australia. Br J Ophthalmol. 2000; 84: 289-92.
28. Pavisic Z. The corneal astigmatism in cases of pterygium.
13. Waller SC, Adamis AP. Pterygium. In: Tasman W, Jaeger ED editors. Ophthalmologica. 1952; 124: 57
Duane’s Clinical Ophthalmology. 2nd ed. Philadelphia: Lippincott-
Raven; 1996; p. 61-3. 29. Noor RAM. Primary pterygium in a 7 year old boy: A report of a rare
case and dilemma of its management. Malaysian J of Medical Sci.
14. Tan DTH, Lim ASM, Goh HS, et al. Abnormal expression of tumor 2003; 10 (2): 91-92.
suppressor gene in the conjunctiva of patients with pterygium. Am J
Ophthalmol. 1997; 123 (3): 404-5. 30. Salomao DR, Mathers WD, Sutphin JE, et al. Cytologic changes in
the conjunctiva mimicking malignancy after topical mitomycin C
15. McCarty CA, Fu CL, Taylor HR. Epidemiology of pterygium in chemotherapy. Ophthalmol. 1999; 106: 1756–60
Victoria, Australia. Br J Ophthalmol. 2000; 84: 289-92

56 l DOS Times - Vol. 19, No. 7 January, 2014

Ocular Involvement in Epidemic MiscMeilslcaelnlaenoeuouss
Dropsy, a Serious Concern
Sanjay Teotia
MS, FICO

Sanjay Teotia MS, FICO
Deptt. of Ophthalmology, Combined Distt. Hospital, Sanjay Nagar, Ghaziabad (U.P.)

Epidemic Dropsy (Argemone poisoning) is a disease Figure 1: Argemone Mexicana
that occurs due to the use of mustard oil contaminated
with the seeds of a poppy weed, Argemone Mexicana Figure 2: Bilateral Pitting edema
(Figure 1), which grows commonly in mustard crops www. dosonline.org l 57
and contains toxic alkaloids, Sanguinarine and
Dihydrosanguinarine. This substance interferes with the
oxidation of Pyruvic acid, which accumulates in the blood
and tissues of the patient. Epidemic Dropsy occurs in
groups of people pertaining of the same food contaminated
with mustard oil1. Epidemic Dropsy causes widespread
capillary dilatation, proliferation and increased capillary
permeability. Other major symptoms are bilateral pitting
edema of extremities (Figure 2), headache, nausea, vomiting,
loose bowels, erythema, breathlessness, symptoms and
signs of cardiac failure which may be fatal and fever2. An
erythematous mottling of the skin may follow the oedema
and haemangiomatous tumours up to 1 cm in diameter
may appear in skin or mucosal surface.
Ocular manifestations in Epidemic dropsy are glaucoma,
subconjunctival haemorrhages, dilatation and tortuosity
of retinal veins, superficial retinal haemorrhages,
microaneurysm, papillophlebitis, disc edema, peripapillary
edema3.
Aetiology
Based upon numerous epidemiological and clinical studies
and human and animal feeding trials, it has been firmly
established that Argemone oil is responsible for epidemic
dropsy4. It occurs due to the use of contaminated mustard
oil (with which Argemone oil is completely miscible)5 for
cooking and massage6. Other contributory factors are the
consumption of a diet rich in carbohydrates and low in
proteins, as well as poor premorbid nutritional status. It has
been observed that those consuming a protein rich diet tend
to develop a relatively mild form of dropsy7. The active

Miscellaneous

toxic principle of Argemone oil, the alkaloid Sanguinarine, sold. Due to a decrease in toxicity during storage of oil, the
is able to withstand normal working temperature and incidence is lowest in April”.
hence appears to be heat stable. Minimum concentration Ocular features of Epidemic dropsy
of 1% of Argemone oil as an adulterant was necessary to Reported ocular features of epidemic dropsy include
produce clinical features8. The duration of exposure is also glaucoma, subconjunctival haemorrhages, dilatation
of vital importance. Sanguinarine can be retained in the and tortuosity of retinal Vessels, superficial retinal
gastrointestinal tract, liver, lung, kidney, heart and serum, hemorrhages, microaneurysm, papillophlebitis and disc
for up to 96 hours after ingestion, due to binding to plasma edema16-19. It has been seen that young individual being
proteins9,10. This may lead to cumulative toxicity even with more susceptible to the disease. Each tissue has different
low dose exposure over prolonged period11. susceptibility to toxin. Within the eye itself, the fundus
Pathophysiology of Epidemic Dropsy changes and glaucoma occur independently. Glaucoma
The exact pathophysiology of epidemic dropsy is not well in epidemic dropsy is toxic and hyper secretary glaucoma,
understood. Sanguinarine and Dihydrosanguinarine have is characterized by headache, colored haloes, normal or
been shown to produce widespread capillary dilatation deep anterior chamber, an open angle of anterior chamber
coupled with increased papillary permeability and and marked elevation of Intraocular pressure associated
produces clinical features similar to epidemic dropsy under with generalized edema of the body Glaucoma is usually
experimental conditions12. The chief effects of Argemone bilateral. Epidemic dropsy glaucoma is non congestive in
oil are on the blood vessels13. Where they cause leakage nature and is caused by the toxic action of Sanguinarine,
of protein rich plasma components into the extra vascular an active alkaloid in seeds of Argemone Mexicana.
compartment, leading to a state of hypovolemia and Sanguinarine causes generalized capillary dilatation
reduced plasma osmotic pressure. The resultant decrease and increased formation of aqueous humor resulting in
in renal blood flow sets into motion compensatory marked rise of intraocular pressure20. The rise of intraocular
mechanism with activation of the renin, angiotensin pressure tends to develop four to eight weeks after the
aldosterone system and retention of sodium and water. onset of dropsy. Prominent vascular pulsations are usually
The fluid and salt thus conserved may compensate for the present in most cases with glaucoma, visual field defects in
expanded vascular capacity and increased permeability epidemic dropsy occurs independently of the rise of I.O.P.
in mild cases of epidemic dropsy. However, in severe and more frequently in early stage of disease21. Aqueous
cases these compensatory mechanisms may prove to be biochemical analysis revealed increased total protein level.
inadequate because fluid and salt conserved by kidneys Aqueous bio assay shows significant elevated prostaglandin
is poorly held in the vascular compartment due to low E2 level and histamine activity. Trabecular meshwork
plasma osmotic pressure. As a result, a state of relative usually remains normal in epidemic dropsy glaucoma.
hypovolemia exists, which provides a constant stimulus for Prostaglandin and histamine release may have significant
renal conservation of salt and water, which in turn caused role in it’s pathogenesis. Usually incidence of glaucoma
marked anasarca. The hypoproteinaemia observed in remains variable in epidemic dropsy. Fundus examination
dropsy may result from leakage of protein rich plasma into in case of epidemic dropsy usually shows venous dilatation,
extravascular tissue, poor intake, diarrhea and perhaps from tortuosity and superficial retinal hemorrhages (Figure 3) of
mild hypotoxicity or protein losing enteropathy. Increased variable size scattered all over the fundus22.
total protein content of the aqueous humor of the eye has On fundus examination toxic vasculitis was also observed.
been demonstrated14. Widespread capillary dilation and Severity of epidemic dropsy was fairly closely related to
proliferation in the subcutaneous tissue, surrounded by retinal venous engorgement. Cases with mild to low grade
proliferating endothelial cells, which produces mottling symptoms had no venous engorgement, while subacute
and blanching of the skin has also been reported. Increased type of cases showed engorgement of the retinal veins.
permeability of these small capillaries leads to oedema, Acute fulminating cases had venous engorgement together
which in the later stages may be worsened by right sided with haemorrhage. Gonioscopy reveals open angle of
heart failure. The dependent oedema in epidemic dropsy is anterior chamber and there is no clogging of angle of
relatively resistant to diuretics and resolves gradually over anterior chamber and trabecular meshwork.
months. It may be firm at times, perhaps indicative of the Stoppage of consumption of adulterated mustard oil,
high protein content of the oedematous fluid. Carbonic anhydrase inhibitor and b blocker like timolol
Persons of all ages affected except breast fed infants and meleate normalize the I.O.P. Multi drug therapy for
toddlers who have no mustard oil in their diet. The disease prolonged period should be used since glaucoma is self
is seen mostly in epidemic form but isolated cases also limited. Refractory cases may need filtration operation.
occur occasionally15. Both sexes are affected equally. In Trabeculectomy should only be done when maximal medical
India the incidence reaches its peak in July to August, when therapy fails. Glaucoma may need operative intervention
newly extracted oil harvested towards the end of summer is but generally responds to Medical management.

58 l DOS Times - Vol. 19, No. 7 January, 2014

Miscellaneous

Figure 3: Venous Dilatation Tortuosity
& Retinal Haemorrhage

Figure 5: Fundus Photographs and OCT Picture
of Central Serous Retinopathy

Figure 4: Subconjunctival Haemorrhage oedema and peripapillary dry spillage. Presence of positive
angiographic findings correlated well with the severity
Subconjunctival haemorrhage is seen in some cases of of the systemic disease, glaucoma however revealed no
ocular epidemic dropsy, this may be due to dilatation correlation23.
and tortuosity of vessels. Sub conjunctival haemorrhage Prostaglandins (especially PGE2) have been implicated
(Figure 4) is a symptomless, condition and there may be and increased levels of PGE2 can cause an increase in the
symptoms of associated causative disease. On examination secretion of aqueous humour and lead to hypersecretary
subconjunctival haemorrhage looks as a flat sheet of glaucoma.
homogeneous bright red colour with well defined margins. Central serous retinopathy chorioretinooathy (C.S.R.)
Most of the time it is absorbed completely within 7 to 21 (Figure 5) is a unique feature, although rarely seen in
days. In case of subconjunctival haemorrhage treat the epidemic dropsy patients. This may be caused by choroidal
cause, cold compress to check the bleeding in the initial vasculature hyperpermeability and leakage24,25 induced
stage and hot compress may help in absorption of blood by prostaglandins or histamine. It causes deterioration of
in late stages. vision in dropsy patients due to macular involvement and
Retinal changes include venous dilatation and tortuosity, may lead to permanent visual deficit even after resolution
haemorrhages and optic disc oedema. Fundus fluorescein of disease. Sometimes disc oedema may be seen due to
angiography shows relevant angiographic findings include toxic optic neuropathy induced by sanguinarine.
dilatation and tortuosity of retinal veins, prominent vascular Superficial retinal haemorrhages (Figure 6) occured
staining, blocked fluorescence, microaneurysm, disc as a result of toxic vasculitis. They appear to be due
to toxic action of Sanguinarine on blood vessels,
particularly on veins. There are various causes of retinal

www. dosonline.org l 59

Miscellaneous

Figure 6: Superficial Retinal Haemorrhage Figure 7: Retinal Microaneurysm

haemorrhage like hypertension, retinal vein occlusion Figure 8: Papillophlebitis
and Diabetes Mellitus etc. In case of epidemic dropsy Figure 9: Disc edema
haemorrhage occurs from tortuous retinal vessels, which
are easily damaged. Retinal haemorrhages that take place
outside macula can go undetected for many years and
may sometimes be found during ophthalmoscopic and
fundus examination of eye. Some retinal haemorrhages
can cause severe visual impairment especially when it
involves macular area. Superficial retinal haemorrhages in
epidemic dropsy will normally resorb without treatment as
the disease subsides.
Microaneurysm (Figure 7) if present in ocular epidemic
dropsy are due to non inflammatory capillary dilatation.
Retinal microaneurysms are tinny areas of blood protruding
from an artery or vein in the back of retina. These protrusions
may leak blood into retinal tissue. Microaneurysms usually
have no symptoms unless associated with some other
pathology. A microaneurysm does not require any treatment.
As the epidemic dropsy subsides, microaneurysms usually
diminished.
Papillophlebitis (Figure 8) is also a ocular manifestation
of Argemone mexicana oil toxicity. Patient may present
with mildly reduced visual acuity, visual field or both.
In ophthalmic dropsy, Papillophlebitis is due to dilated
and tortuous retinal veins. Because in this condition
papillophlebitis is non ischemic so the prognosis is good.
Disc edema (Figure 9) seen in some patients is due to intense
non-inflammatory capillary dilatation. This is usually
associated with peripalliary edema. Most of the patients
with disc edema have cardiovascular decompensation.
Which progresses to congestive cardiac failure with a high
mortality. It can later on, result in secondary optic atrophy.
Investigations
Complete eye examination is required including vision,
fundus, Intraocular pressure and visual field examination.
Alongwith this fluorescein angiography and optical
coherence tomography is also required in some cases.

60 l DOS Times - Vol. 19, No. 7 January, 2014

Miscellaneous

Specific investigation should be done for detection of Diuretics are used universally but caution must be exercised
Argemone oil adulteration in edible oils. not to deplete the intravascular volume unless features of
Nitric acid test, 5ml oil is shaken with an equal volume frank congestive cardiac failure are present, as oedema is
of nitric acid. On standing, the acid layer turns yellow, mainly due to increased capillary permeability.
orange yellow or crimson, depending upon the amount of Glaucoma, which is the commonest ocular manifestation
Argemone oil. The test is sensitive to a concentration of in dropsy generally responds to medical management but
more than 0.25%. It has a high false positive rate and a sometimes may need operative intervention, when maximal
positive test must be confirmed. medical therapy fails. Other ocular involvements should be
Ferric Chloride test 2ml of oil and 2 ml of concentrated managed accordingly. Prognosis in ocular involvement in
hydrochloric acid are mixed and heated in a water bath dropsy is usually good because as the disease improves
at 33.5-350C for two minutes. Then 8 ml of ethyl alcohol most of the ocular manifestations will also improves but
is added and the mixture is heated in the bath for one precautions must be taken to prevent further complications.
minute. Finally 2ml of ferric chloride is added and the tube Investigate the case thoroughly and manage accordingly.
is heated in the bath for a further 10 minutes. If Argemone Summary
oil is present, an orange red precipitate is formed. Ocular involvement in epidemic dropsy occurs due to use
Cupric acetate test, a green colour is formed. of mustard oil contaminated with the seeds of a poppy
Paper chromatographic method: It is the most sensitive weed, Argemone Mexicana. Which contains toxic alkaloids
method and can detect down to 0.0001% Argemone oil sanguinarine and dihydrosanguinarine, that interferes with
adulteration26. Diagnosis is made on the basis of clinical the oxidation of Pyruvic acid, which accumulates in the
signs and symptoms of dropsy, ocular signs, symptoms. blood and tissues of the patient. In this disease their occurs
History of use of edible oils adulterated with argemone widespread capillary dilatation., proliferation and increased
mexicana oil and other persons residing nearby locality capillary permeability. The chief effects of Argemone oil are
are also suffering from same disease. Specific investigation on blood vessels. Where they caused leakage of protein rich
for detection of argemone oil adulteration in edible oil plasma components into the extravascular compartment,
confirms the diagnosis. leading to a state of hypovolemia and reduced plasma
Prevention osmotic pressure.
All contaminated mustard oil excluded: Steps should be Ocular manifestations in epidemic dropsy are various but
taken to prevent contamination of mustard crops with Glaucoma is commonly seen. Others are dilatation and
the weed, Argemone mexicana. Selective Cultivation of tortuosity of retinal veins, Superficial retinal haemorrhages,
yellow seeded mustard with which neither black coloured microaneurysm, papillophlebitis, disc edema and
Argemone seeds nor dark brown Argemone oil mixes well peripapillary edema.
so that adulteration can easily be detected even with naked In case of epidemic dropsy increased total protein content
eye. A strict ban on the sale of unbranded and unpacked of the aqueous humor of the eye has been demonstrated. It
mustard oil. Education and motivation of farmers to has been observed that those consuming a protein rich diet
cultivate yellow seeded mustard and to make them aware tend to develop a relatively mild form of dropsy. In eye,
of the identity of Argemone plants. Which grow as weeds the fundus changes and glaucoma occur independently.
in mustard fields. Glaucoma in epidemic dropsy is hyper secretary glaucoma.
Government agencies involved in enforcing the provisions Epidemic dropsy glaucoma is non congestive in nature,
of the prevention of food adulteration act must be made sanguinarine causes increased formation of aqueous humor
accountable in the event of occurrence of such epidemics. resulting in marked rise in intraocular pressure. The rise of
This means exemplary punishments for unscrupulous Intraocular pressure tends to develop four to eight weeks
traders. after the onset of dropsy. Visual field defect in epidemic
Management dropsy occurs independently of the rise of I.O.P. and
Withdrawal of the contaminated cooking oil is the most more frequently in early stage of disease. Prostaglandin
important initial step. Bed rest and protein rich diet are and histamine release may have significant role in it’s
useful. Supplements of calcium, antioxidants, Vitamin pathogenesis. On fundus examination there will be venous
C, E, thiamin and other B vitamins are commonly used. dilatation and tortuosity, superficial retinal haemorrhages
Corticosteroids and anthihistaminics such as promethazine and toxic vasculitis may be seen. Gonioscopy reveals
have been advocated by some investigators, but open angle of anterior chamber. Glaucoma may need
demonstrated efficacy is lacking. surgical intervention but generally responds to medical
management. Fundus Fluorescein angiography shows
dilatation and tortuosity of retinal veins, prominent vascular

www. dosonline.org l 61

Miscellaneous

staining, microaneurysms and disc oedema. Prostaglandins 8. Lal S.B., Epidemic dropsy in Bihar. Indian Med Gaz. 1951;
can cause vascular dilatation, hyperpermiability with serious Feb;86(2):64-71
exudation and Superficial retinal haemorrhages. Central
serous retinopathy (CSR) is a unique feature, although rarely 9. Sanyal P.K., Argemone and mustard Seeds. Indian med. Gaz. 1950;
seen in epidemic dropsy. It causes deterioration of vision in Nov;85(11):498-500.
dropsy patients due to macular involvement. Disc oedema
may be seen due to toxic optic neuropathy induced by 10. Sood N.N., Sachdev M.S., Mohan M., et al. epidemic dropsy
sanguinarine. Superficial retinal haemorrhages occurs due following transcutaneous absorption of Argemone Mexicana Oil.
to toxic action of sanguinarine on blood vessels, particularly Trans R. Soc. Trop. Med. Hyg. 1985; 79 : 510-12.
on veins. Microaneurysms present in ocular epidemic
dropsy are due to non inflammatory capillary dilatation. 11. Sinani G.S., Epidemic dropsy. In : Ahuja MMS, ed, Progress in
Papillophlebitis is also a ocular manifestation of Argemone Clinical medicine in India. (Arnold Heinemann Publishers, India) PP
Mexicana oil toxicity. Disc edema seen in some patients is 1976; 92-104.
due to intense non inflammatory capillary dilatation. This
is usually associated with peripapillary edema. Complete 12. Lal R.B., Das gupta A.C., Investigation into epidemiology of epidemic
eye examination along with specific investigation to detect dropsy XA note on an outbreak of epidemic dropsy associated with
Argemone oil adulteration in edible oil like Nitric Acid Test, the use of mustard oil pressed from adulterated seed. Indian J. Med.
Ferric Chloride Test, Cupric acetate test should be done to Res. 1941; 29 : 157-63.
confirm the diagnosis. All contaminated mustard oil should
be excluded to prevent the disease. Management requires 13. Upreti K.K., Das M, Kumar A, Singh G.B., et al. Biochemical
withdrawal of contaminated cooking oil, bed rest, protein toxicology of Argemone oil : Short term oral feeding response in
rich diet, antioxidant suppliments helps in indprovement rats. Toxicology 1989; 58 : 285-98.
of the disease. Corticosterioids and antihistaminics such as
promethazine are also helpful Diuretics are used universally 14. Tandon S., Das M., Khanna S.K., Biometabolic elimination and
but with caution. Glaucoma, which is the commonest organ retention profile of Argemone alkaloid, Sanguinarine, in rats
ocular manifestation of dropsy generally responds well to and guinea pigs. Drug Metab Disp. 1993; 21:194-97.
medical management but sometimes require surgery. Other
ocular involvements should be managed accordingly. 15. Chakravarty N.K., Chaudhuri R.N., Production of epidemic dropsy
References in monkeys, Indian Med. Gaz. 1951; 86:392-97.

1. John Macleod, Tropical Diseases and Helminthic, Infections, 16. Manson Bahr PEC, Apted FIC; Plant poisons, in Manson Bahr PEC,
Epidemic Dropsy (Argemone poisoning), Davidson’s principles and Apted FIC (eds) : Manson’s Tropical diseases, ed 18, London, English
practice of Medicine, 1982; 13:892-93. Language book Society and Bailliere Tindal, 1982; 571-72.

2. Sharma B.D., Malhotra S., Bhatia V., Rathee M. “Epidemic dropsy in 17. Tandon R.K., Singh D.S., Arora R.R. et. Al : Epidemic dropsy in New
India’. Postgraduate medical Journal, Nov. 1999; 75 (889): 657-61. Delhi, Am. J. Clin, Nutr: 1975; 28: 883-87.

3. Rathore M.K. Ophthalmological Study of epidemic dropsy. Br. J. 18. Mohan M, Sood NN, Dayal Y. et. Al. ocular and clinical
Ophthalmol. 1982; 66 : 573-75. epidemiological study of epidemic dropsy: Indian J. Med. Res: 1984;
80:449-56.
4. Bhende Y.M., Vascular Changes produced by Argemone Oil II.
Changes in rats given injection of the oil. J. Postgrad. Med 2: 185-91. 19. Sachdeva S.S., Sood NN, Sachdeva H.P.S., et al. Optic disc Vasculitis
in epidemic dropsy. Jpn. J. Ophthalmol 1987; 31;467-72.
5. Chakravarty NK, Chaudhuri RN, Werner G.. Observations on
Vascular Changes produced by Argemone alkaloids, Indian J. Med. 20. Singh K., Singh MJ, Das JC: Visual field defects in epidemic dropsy;
Res. 1955; Jan;43(1):107-12. clin. Toxicol (Rhila), 2006; 44(2):159-63.

6. Sachdev M.S., Sood N.N., Verma LK., et al. Pathogenesis of epidemic 21. M.K. Rathore; ocular manifestations of epidemic dropsy; Indian J.
dropsy glaucoma. Arch Ophthalmol. 1988; 106 : 1221-23. Ophthalmol.1982; 30 (4), 307-09.

7. Lal R.B., Roy S.C. (1937) Investigation into epidemiology of 22. M.K. Rathore; ophthalmological study of epidemic dropsy; British. J.
epidemic dropsy: Introductory notes and historical Survey. Indian J. Ophthalmol. 1982; (66)573-75.
Med. Res. 25 : 163-67.
23. Sachdev MS, Sood NN, Mohan M, et al. optic disc Vasculitis in
epidemic dropsy; Jpn. J. Ophthalmol. 1987; 31(3): 467-74.

24. Peyman GA, Choroidal hyperpermiability in Central serous
Choroidopathy: A new concept. Arch ophthalmol. 1995; 13:701-2.

25. Atul Kumar, Tanuj Dada; Epidemic dropsy: An ophthalmic View
point; The National Medical Journal of India, 1999; Vol. 12, No. 5.

26. Singh GB, Khanna S.K., Argemone Mexicana Strikes again. Sci. Rep.
1983; 20 : 108-10.

62 l DOS Times - Vol. 19, No. 7 January, 2014

Evolution of Refractive RefraEctvivoelSuutrigoerny
Surgery
Hemant Kamble
MD

Hemant Kamble MD
R.P. Centre of Ophthalmic Sciences, AIIMS, New Delhi

Refractive surgery is a category of treatment designed to anterior and posterior keratotomy to clinical practice in
induce structural changes in the eye with the intent of hundreds of patients and reported his results in the early
altering its refractive status. There are two broad categories 1940s.
of refractive surgery: Keratorefractive, during which In the autumn of 1948 Harold Ridley, noted no ill effects
the physical architecture of the cornea is altered; and from stationary particles of PMMA in eyes of Royal Air
Intraocular, during which synthetic lenses are placed into Force pilots. This led him to fashion a lens of PMMA and
the eye, with or without removal of the natural crystalline the modern era of intraocular lens implantation for cataract
lens. surgery was born.
Barraquer3 in 1949 described the principles of lamellar
Advent of Refractive Surgery surgery. He changed the cornea’s shape by removing the
Leonardo da Vinci contemplated the possible source anterior cornea with microkeratome, freezing it, and using
of visual disturbances, leading to the study of refractive a cryolathe to change its shape. In 1985 Casimir Swinger
errors in early 16th century. With the development of the developed a method of changing the shape of the cornea
keratometer in 1867, surgeons could measure astigmatism without freezing it. Luis Ruiz in 1987 used an automated
following cataract surgery. Snellen1 in 1869, proposed a instrument to perform the operation directly on the eye.
method to treat astigmatism, using incisions across the This procedure, called automated lamellar keratoplasty
steep meridian of the cornea to flatten it. (ALK).
By the mid-1970s, Russian scientists such as Durney,
Trials and Experimentation Yenaleyev, and Fyodorov4-17 had determined that most of
In 1850s a Dutch physician, Leendert Jan Lans began the radial keratotomy flattening effect could be obtained
to study and define the principles of keratotomy which with sixteen or fewer incisions placed only on the anterior
became the standard of refractive surgery. He practiced cornea. Fyodorov developed a system of anterior radial
and promoted the principles of corneal flattening that could keratotomy that, by varying the number of incisions and
be achieved by incisions made on the anterior surface of the amount of uncut clear central zones between them,
the cornea. By varying the number, direction, and shape of permitted him to carefully control the degree of visual
the incisions, Lans could manipulate the effects and tailor correction.
the visual correction. Radial keratotomy was introduced into the United States
In addition to surgical techniques, there were nonsurgical in 1978 by Leo Bores. In 1980 the National Institutes of
attempts at reducing myopia by manipulating the shape of Health sponsored the PERK18 (Prospective Evaluation of
the eye like an eye cup or a firm rubber band used to flatten Radial Keratotomy) study which provided factual, scientific
the cornea. But these were techniques that failed to result data on radial keratotomy performed in a standard manner
in any significant degree of visual correction. in nine centers across the United States.

Pioneers of Modern Refractive Surgery
Tsutomu Sato2 in 1936 observed a flattening of the cornea
in patients with traumatic injury to the eyes. He brought

www. dosonline.org l 67

Evolution

The Era of Lasers presbyopia correction, femtosecond lenticule extraction,
In 1960s, argon laser was first used to treat retinal disease, small-incision lenticule extraction, and intrastromal
and the neodymium-doped yttrium aluminum garnet presbyopia correction (INTRACOR)
(Nd:YAG) laser was first used in 1979 to treat capsular Intrastromal Corneal Ring Segments
opacity. The intrastromal ring concept was proposed by Reynolds
Thermal shrinkage of the cornea thereby changing corneal in 197826. It was first evaluated as a treatment for myopia
contour was demonstrated by Beckman and Peyman and by Keravision. INTACS technology for myopia received
their associates in 1980’s. The ability of Argon-fluoride European CE Certification in 1996 and Food and Drug
excimer laser to indent eye tissue without causing collateral Administration (FDA) approval in 1999. This technology
tissue damage was reported by John Taboada19. Dr. Stephen was then adopted for the treatment of keratoconus.
Trokel demonstrated that Argon fluoride laser (193nm) In 2004, INTACS (sizes 0.25-0.35mm) were given an
could be used to ablate organic tissue. After experiments FDA Humanitarian Device Exemption for their use in
with animal corneas, Trokel and Srinvasan20-21 in 1983 keratoconus. In 2010, the exemption was extended to
published an article introducing the concept of using the include the 0.4 and 0.45 mm rings.
excimer laser for refractive surgery. There are four types of ICRS which differ in geometrical
Excimer laser on blind human eyes were first used by Seiler, profile and diameter: 1) INTACS (Addition Tecnology Inc.,
a German ophthalmologist. He attempted to reproduce the Sunnyvlae, CA, USA), 2) Ferrara rings (Mediphacos, Belo
keratotomy procedures but could not succeed. Formula Horizonte, Brazil) 3) Bisantis segments (Opticon 2000 SpA
to determine the amount of tissue removal necessary Soleko SpA) and 4) Myoring (DIOPTEX)
to reshape the cornea to induce a change in the cornea Refractive Lenticule Extraction
refraction was developed by Charles Munnerlyn22, a laser Refractive lenticule extraction for the correction of myopia
engineer. He designed the first excimer laser intended and myopic astigmatism has developed at a rapid pace
to reshape the cornea and the procedure was called all over the world. This surgical technique is based on
photorefractive keratectomy (PRK). First PRK in the United cutting tissue using the VisuMax femtosecond system
States was performed by Dr. Marguerite McDonald in 1988. (Carl Zeiss Meditec, Germany), instead of ablation with an
Shortly thereafter, clinical trials began and the procedure excimer laser. ReLEx comprises two different techniques.
was approved in the United States in 1995. In ReLEx flex27 (Femtosecond Lenticule Extraction) a lens-
Pallikaris and Buratto23-24 and their associates in 1990’s, shaped piece of corneal tissue (lenticule) is cut with the
combined lamellar splitting with excimer laser ablation of femtosecond laser and then removed via flap like access
the exposed corneal bed. Pallikaris termed this combination cut. In the more advanced Small Incision Lenticule
LASIK (laser in-situ keratomileusis). Extraction version known as ReLEx smile28, the lenticule is
The initial clinical trials of LASIK in the United States began removed via a small incision measuring just 2 to 4 mm as a
in 1996. LASIK procedure was US FDA approved in 1999. minimally invasive technique
The first Ophthalmic Femtosecond laser system was The US Clinical Trial of ReLex smile commenced in June
designed by Dr Juhsaz in collaboration with Dr Kurtz at the 2012 and first results were presented by Dr. Dishler in
University of Michigan in the early 1990s. Femtosecond April 2013. The study is being conducted at five sites in the
laser is an infrared laser with a wavelength of 1053nm and United States and 238 patients have been treated. The FDA
works by producing photodisruption or photoionization of granted approval to expand the study to the full cohort of
the optically transparent tissue such as the cornea25. The 360 subjects (Phase III clinical study) in Nov 2013.
technology of FS laser has evolved significantly from its Intraocular Implants
introduction. Laser firing frequency has increased from 10 The phakic myopia lens was introduced by Strampelli29
kHz in 2002 to 150 kHz in fifth generation IntraLase FS and later popularized by Barraquer30 in the late 1950s.
system. The higher frequency allows reduced flap creation These lenses were abandoned following serious angle-
time and lower energy per pulse leading to a smoother and endothelium-related complications. In the mid 1980s,
corneal stromal bed. Dveli restarted phakic myopia lenses with 4 soft angle-
Femtosecond laser approved for bladeless LASIK in the supported loops. Fyodorov introduced the concept of a soft
United States was the IntraLase laser, which gained FDA phakic lens in the space between the iris and the anterior
approval in 2001. Femtosecond laser has a wide range of surface of the crystalline lens.
applications in corneal refractive surgery. This includes Worst31, who introduced the iris claw lens in 1977,
LASIK flap creation, astigmatic keratotomy, channel creation implanted an opaque iris claw lens in the phakic eye of a
for implantation of intrastromal corneal ring segments,

68 l DOS Times - Vol. 19, No. 7 January, 2014