DOS Times Jan'15

Delhi
Ophthalmological
Society

Contents

5 Editorial Miscellaneous

Experts’ Corner 43 Vitreomacular Traction: Management

13 Phakic IOL Raji K., A.K. Upadhyay, S. Waikar, P. Tiwari

Evolution

Theme: Refractive Surgery 49 Presbyopia- Evolution and Current
Management
19 Trifocal IOLs Vijay Kumar Sharma, Tarun Arora,
Tarun Arora, Vijay Kumar Sharma, Rajesh Sinha
Rajesh Sinha, Jeewan S. Titiyal
Topography Guided Kerato-Refractive PG Corner
23 Surgery
Pooja Bandivadekar, Manpreet Kaur 55 Principles of Kerato-Refractive Surgery
Abhishek Dave, Vinay Arora, Sridevi Gunda,
Prachi Jhala Dave, Umang Mathur
27 LASIK Xtra: What is the Extra Benefit?
Monthly Meeting Corner
Shilpi Diwan, Ritika Sachdev,
Mahipal Singh Sachdev 59 Retained Intraocular Foreign Body

Diagnostics Bhartendu Varma, Nidhi Panwar, S.N. Jha
33
Four Aces of Refractive Surgery: Aberrations, Tear Sheet
Aberrometers, Applications and Advances
Maneck Darius Nicholson, Vishal Arora, 75 Refractive Surgery Pearls
Natasha Pahuja, Rohit Shetty
Vishal Arora, Luci Kaweri, Rohit Shetty

www. dosonline.org l 3

“Tell me and I’ll forget; show me and I may remember; involve me
and I’ll understand”

-Benjamin Franklin

Respected Seniors & Dear Friends,
The annual conference of Delhi Ophthalmological Society is just a few
weeks away and we are working very hard to make it a conference with a
difference. The theme of the conference is ‘Eyennovation’ and in addition to
various innovative techniques and ideas being discussed in this conference,
we also have planned many new innovative sessions and events. For the
first time we are planning to have ‘satellite sessions’ with interactive video
conferencing by eminent international ophthalmologists from around the
world in various sessions at our conference venue. These par excellence
academic discussions with some of the foremost leaders, innovators and
visionaries in Ophthalmology will be one of the prime attractions and will
benefit thousands of delegates. In addition to satellite sessions we also have
a high number of international guest speakers of repute who will enhance
the academic standard of the conference by their knowledge and expertise.
Additionally we are planning for many interactive sessions and wet labs
focussed on individual investigative or management modality. The young
ophthalmologists’ (YO) sessions will be specially meant for our young and
upcoming colleagues. Further we are planning for sessions focussing on
Innovative techniques, interesting case scenarios and interesting videos.
We look forward to a truly mega-academic feast in DOS annual conference
with conglomeration of record number of international faculty from all over
the world to share their techniques and expertise and to make this conference
a grand success, living up to the true tradition of DOS.
Sincerely Yours

Rajesh Sinha
Secretary,
Delhi Ophthalmological Society

www. dosonline.org l 5

Guest Editorial EditoRreifaralctiBveoSaurrgdery

“The only thing that is constant Editor-in-chief
is change -”Heraclitus Rajesh Sinha

The constancy of change for the better defines progress. In the Executive Editor
field of refractive surgery we have been witnessing tremendous
progress not only from the surgeon’s chair but also from the Vijay Kumar Sharma
point of view of patient’s safety and quality outcomes. The word Tarun Arora
“wow” is rarely ever used for any other surgery as much as it is
used for refractive surgical procedures. It is indeed magical how Editorial Board
far we have come in bettering ourselves at invoking this “wow”.
As ophthalmologists of the third millineum we owe it to our patients to find predictable effective methods Ritika Sachdev
to reduce their dependence on their external optical crutches in the form of glasses and contact lenses Sandeep Gupta
irrespective of the kind and extent of refractive error. Ramendra Bakshi
LASIK surgery is among the most commonly performed elective procedures in medicine today1. Right
from the primitive procedure performed by Dr. José Ignacio Barraquer, where he removed, modified Neelima Aron
and reinserted the corneal disc into the patient’s eye2 we have come a full circle with the current SMILE Digvijay Singh
(Small Incision Lenticule Extaction) procedure where the same concept has been modified with extreme Manpreet Kaur
precision and safety. Hemant Kamble
The entire gamut of refractive surgery offers the freedom of choice to the patient and physician, that can Vishnukant Ghonsikar
be tailored to suit each eye keeping in mind patient’s refractive power, corneal thickness, age,economic
condition and other unique requirements. LASIK, though, remains the child star of refractive surgery Ravi B.
having gained insurmountable popularity in its infancy. It has stood the test of time and its modifications Shorya Vardhan Azad
with better microketatomes, femtosecond lasers, optimizations like wavefront, topography guided
ablations ensure that this trend continues. Anirudh Singh
A variety of sophisticated diagnostic tools to analyze corneal topography,aberrometry and ocular Vinod Agarwal
hysteresis help us in understanding each eye better. They help us in spotting potential risks and thus aid Dewang Angmo
in careful patient selection and also pave the way forward for further research and innovation. Surface
ablation procedures alone or in combination with corneal collagen crosslinking, implantable collamer Neha Goel
lenses, presbyopic treatments are all choices that can be opted for in suitable situations. Parul Jain
Now that we understand safety aspect of the procedures and their outcomes better, we must try to Reetika Sharma
avoid all complications in every patient by not only selecting the patients carefully but also offering
them appropriate choices suited to their individual eye status. While the menace of dry eyes is reduced DOS Correspondents
considerably by choosing a flapless procedure, the rate of intra-operative complication related to flaps
is also on a fast decline with the vast use of femtosecond lasers. Supriya Arora
We cannot ignore more and more presbyopic patients asking for independence from glasses just like Prateek Kakkar
their young counterparts, and will need to have an effective answer for them soon enough. A big leap Ruchir Tewari
in the form of multifocal and accommodative intraocular lenses is already a potent solution in patients Vineet Sehgal
who develop cataract. Multifocal laser ablation techniques and corneal inlays are being developed for Kumari Reena Singh
this and the hopes of many may soon be fulfilled3.Technological advance ments in terms of surgical
instruments, biomaterials, and engineering and surgical capabilities have certainly moved surgical Nasreen
restoration of accommodation from a theoretical concept more into real ophthalmic practice, but much Ravish Kinkhabwala
work still remains.
Pulak Agarwal
1. LASIK World Literature Review - Quality of Life and Patient Satisfaction; Kerry D. Solomon, MD et al; Akshay Tayade
Ophthalmology 2009;116:691–701 © 2009 by the American Academy of Ophthalmology. Vaiteeshwaran L.

2. Dan Z Reinstein, Timothy J Archer, Marine Gobbe. Birth of Lasik. The Eye in History 2013;1:431-32. Amar Pujari
3. André AM Torricelli et al. Surgical management of presbyopia. Clinical Ophthalmology 2012:6 1459– Obuli Ramachandran

1466 Advisory Board

Thanks. R.V. Azad Rajendra Khanna
Y.R. Sharma Atul Kumar
Dr. D. Ramamurthy, Chairman, B. Ghosh Lalit Verma
B.P. Guliani J.S. Titiyal
THE EYE FOUNDATION Harbansh Lal Sanjeev Gupta
V.P. Gupta A.K. Grover
582-A, D.B.ROAD R.S. PURAM, COIMBATORE TAMIL NADU Ramanjit Sihota Mahipal S. Sachdev
Praveen Malik Amit Khosla
Cover Designed by: Aman Dua Abhishek Dagar Namrata Sharma
Layout Designed by: Mahender P.K. Sahu Umang Mathur
Published by Dr. Rajesh Sinha for Delhi Ophthalmological Society J.K.S. Parihar J.S. Bhalla
Printers: K.D. Printo Graphics, 2/20, 1st Floor, D.D.A. Market Tanuj Dada Rohit Saxena
Complex, Near SBI, Dr. Ambedkar Nagar, New Delhi, Bhavna Chawla Manisha Agarwal
Email: [email protected] Ruchi Goel Rohan Chawla

www. dosonline.org l 7

Experts’ Corner

Phakic IOL

A Phakic Intraocular Lens (P-IOL) is an artificial lens placed within the eye either immediately in Mahipal Sachdev
front or behind the iris. P-IOLs are designed to correct refractive error without reshaping the cornea D. Ramamurthy
or interfering with accommodation. P-IOLs are approved by the FDA to fully correct up to 15.00 Rajendra Khanna
diopters (D) of myopia. People with more than 15.00 D of myopia may use a P-IOL to reduce Sudarshan Khokhar
their refractive error, but will not achieve full correction. The learning curve for P-IOL surgery is
relatively short, but very steep. If for any reason the P-IOL becomes problematic or undesired, it can
be surgically removed in a process essentially the reverse of implantation. P-IOLs are generally not
ideal for persons over age 45 or anyone who is presbyopic.
Here we discuss the preferred practice patterns with leading experts in this field. The questions have
been prepared by DOS Executive Editor Dr. Tarun Arora (TA): MD, DNB, FICO, Senior Resident,
Cornea, Cataract and Refractive Surgery Services, Rajendra Prasad Centre for Ophthalmic Sciences,
All India Institute of Medical Sciences, New Delhi.

Dr. Mahipal S. Sachdev (MSS): MD, is the Director and Senior Consultant, Cataract and
Refractive Surgery of Centre for Sight Group of Hospitals, New Delhi.

Dr. D. Ramamurthy (DR): MD, is the current Director & Senior Consultant at Eye
Foundation, Coimbatore.

Dr. Rajendra Khanna (RK): Director, Khanna Eye Centre, Nirman Vihar, Vikas Marg,
Delhi.

Dr. Sudarshan Khokhar (SK): MD, is currently Prof. of Ophthalmology in Cataract &
Refractive Surgery Services at Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India
Institute of Medical Sciences, New Delhi.

TA: What are the various investigations and prerequisites while planning a patient
for phakic IOL?

MSS: Phakic IOL candidates require a comprehensive workup to rule out any potential
anatomic or physiological problems. We need to perform corneal topography and measures
anterior chamber depth, which is critical in these patients, and screens for corneal diseases
and keratoconus. The biometry is done to confirm the anterior chamber depth. The white-
to-white measurement is also taken. Specular microscopy is done. Manifest refraction is very
important to confirm refraction stability. Finally, dilated fundus examination and slit lamp
examination is done before the final decision on the patient’s suitability for the procedure is
made.

DR: - Complete eye examination including Refraction, BCVA, anterior segment ,IOP &
fundus evaluation especially macula & periphery.

- AC depth

- White to white

- K readings

- Specular microscopy

- Topography to ensure patient is not suitable for laser vision correction & to evaluate
cornea.

www. dosonline.org l 13

Experts Corner: Phakic IOL

RK: on a measurement of the patient’s white-to-white distance,
a: Refraction which is just an indirect measurement of the sulcus-to-sulcus
length. After having done a huge number of ICLs we’ve
(i) Manifest determined that the best white-to-white measurement is
(ii) Cycloplegic done with digital calipers under microscope magnification,
b: IOP with the patient in a reclined position.
c: Corneal Thickness
d: AC Depth from endothelium To make selecting a lens easier, Staar has an on-
e: Keratometery line sizing and ordering system. The surgeon will go to a
f: White to White from mid limbus to mid limbus website, enter in the patient’s biometry, such as chamber
SK: The investigations for a refractive surgery include depth and white-to-white measurement, and the program
Cycloplegic refraction, UCVA, BCVA, topography, will select the appropriate ICL to order.
Indirect ophthalmoscopy, intraocular pressure (IOP),
central corneal thickness (to find if fit for LASIK), white to DR: Based on the data sent to them the company
white diameter (orbscan IIz), anterior chamber depth (the sends the ICL.
usual cutoff is 2.8 mm), gonioscopy (to rule out pigment
dispersion and concave iris configuration, occludable I cross verify primarily by White to White.
angles/ angle closure).
A patient undergoing Implantable Collamer Lens AC depth & K readings also play a role. Following is
(ICL) should not have irregular astigmatism (some cases the chart I use:
of keratoconus are the newest indication), retinal lattices
holes should be lasered, no history of retinal detachment or WtW (mm) AC Depth Visian ICL Length
glaucoma, normal IOP, ACD>2.8 mm with open angles. 10.65 - 11.14 <3.5 mm 12.1 mm
TA: Which phakic IOL do you routinely implant 11.15 - 11.84 <2.95mm 12.6 mm
in your practice and what are your results with the 11.15 - 11.64 >3.0 mm 12.6 mm
same? 11.65 - 12.3 3.0 - 3.5 mm 13.2 mm
MSS: I normally use Star Visian ICL™ by Surgical. 11.85 – 12.5 <3.0 mm 13.2 mm
Visual outcomes are good. Now they have comeup with 12.4 - 12.9 >3.1 mm 13.7 mm
Centraflow in which peripheral iridotomy is not required.
In patients who can not afford Implantable Phakic Contact RK: Measurement from White to White and AC
Lens (IPCL, Phakic Lens, Care Group, India) is also an Depth are important.
option.
DR: ICL & recently have tried a few IPCL. SK: ICL is sized based on white to white diameter
The results are extremely good, with excellent calculated on Orbscan. If there is a discrepancy between
correction, stability and no deterioration in the quality of the two eyes, we use calipers to confirm the white to white
vision. diameter.
RK: IPCL (Implantable Phakic Contact Lens)
The results are predictable and safe TA: For what degrees of astigmatism would you
SK: With the introduction of V4c with centraflow prefer toric ICLs? Have you observed any rotation in
technology, we have shifted completely to its use without postoperative periods?
doing a preoperative laser iridotomy in these patients.
TA: How do you select the appropriate size of MSS: We prefer to correct astigmatism upto 5 D, but
ICL? IPCL can be customized for a correction of upto 10 D of
MSS: Proper calculation of sizing very important, astigmatism.
because sizing will determine the fit and overall success of
the procedure. Selecting the appropriate lens size is based Toric ICLs are very stable in the post-operative
period. Occasional cases may require redialing. Repeated
rotation of ICL even after redialing, though rare, may be
observed due to sizing issues and may require replacement
of ICL (of another size).

DR: Anything beyond .75 D of astigmatism we
offer Toric ICLs. Less than that we use a spherical ICL and
position the 3 mm incision on the steep axis to de-bulk the
astigmatism.

If the sizing is correct there is no tendency for these
lenses to rotate.

RK: I prefer a Toric ICL in astigmatism from 1D to
7D. Yes, occasionally.

14 l DOS Times - Vol. 20, No. 7 January, 2015

Refractive Surgery

SK: We implant TICL in cases of regular myopic Over-expectation by the patient should be tackled
astigmatism with cylinder exceeding 1D. TICL shows good with preoperatively.
results postoperatively in such eyes with no incidence of
postoperative rotation in our cases. All borderline cases should be avoided.
For toric ICL, preoperative corneal axis marking is
TA: What are the pearls and pitfalls while essential in a sitting position.
implanting ICL?
TA: What complications have you encountered
MSS: First and foremost proper loading of ICL should in your phakic IOL practice? How did you manage the
be ensured. Improper loading can lead to upside down ICL same?
in anterior chamber and breakage of ICL. Pupil should be
fully dilated and patient should be comfortable. We do this MSS: In our practice, after doing phakic IOLs in
procedure under topical anaesthesia. Second important a large number, I can say that its a very safe procedure.
step is doing Iridectomies - One should ensure that PIs Though rare we have encountered few complications as
should be superior and peripheral enough to allow a patent glare, postoperative inflammation, transient increase in
opening, which is important, but not so large that they intraocular pressure, cataract which was subsequently
create glare or polyplopia. managed with cataract surgery and implantation of IOL. In
cases of Toric ICL sometimes rotation is also a problem for
DR: - Perfect loading which redialling is required. Being a tertiary care centre we
- Incision size of 3 mm have also we have also seen retinal detachment and acute
- Not wound assisted but with the mouth of the postoperative endophthalmitis. There was one referred case
cartridge in the AC. Gives better control while implanting. of bilateral acute post-operative endophthalmitis post ICL.
- Ensure the ICL opens in the correct manner & not We prefer to do one eye at a time to avoid this devastating
in the reverse complication.
- You retain control over the ICL even after 7/8th has
been injected in AC. If tendency to open in the reverse DR: A) Raised IOP:
manner, withdraw the lens, reload & re-inject. Causes:
- Always inject in AC & then tuck the haptics behind - Retained viscoelastics
the iris. - Inflammation
- Avoid overfilling viscoelastics in AC. - Excessive vaulting causing crowding of the angle
- Ensure complete visco removal at the end of surgery. (rare)
- Avoid instrument touch on the central thin optics - Inadequate PI (in the older lenses without the hole)
(50 microns). Treatment:
- In toric ICLs ensure it is well aligned at the end of Medical management
surgery after removing speculum. Enlarge PI.
RK: a: Care during Loading B) Corneal edema & iritis - medical management
b: Not to use High Molecular weight Viscoelastic C) Inappropriate refractive outcome due to wrong
c: Protect the natural lens and avoid touching it with positioning of ICL.
any instrument While inserting IPCL Verify and if confirmed rotate the ICL to the right
d: Avoid touching the Optical Zone of IPCL with any axis.
instrument D) Anterior sub capsular cataract - (just 3 out of >
e: Visco removal at the end should be meticulous 1500 in our series) where there was significant Vision drop
f: Wound sealing should not be very tight - explant ICL, Phaco and implant IOL.
g If the lens does not open properly then do not E) Retinal detachment - predisposed due to high
manipulate in the anterior chamber. Bring the lens out myopia.
politely, Reload and Reinsert. -Thorough preop retinal evaluation and prophylactic
h: Check IOP after 3 hrs treatment if necessary.
SK: Patient selection is the most important prerequisite - Avoid chamber IOP fluctuations during surgery.
for any refractive surgery. - Surgery if presents with retinal detachment.

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Experts Corner: Phakic IOL

F) Low or excessive vault: observe if no cataract or RK: Corneal refractive procedure is preferable.
raise in IOP. SK: RLE has its own complications like retinal
detachment, CME, PCO formation, inflammation, haloes,
RK: a: High Post Op. IOP, ... Managed with IV requirement of near vision glasses etc. Therefore, in a
Mannitol young patient we prefer to perform Bioptic surgery, that
is combine LASIK with ICL. However in a patient who
b: Left behind Visco causing reaction ..... Managed presents with presbyopic symptoms or a middle aged
by repeating Irrigation Aspiration person with very high myopia, RLE is a better option.

c; Rotation of Toric IPCL .... Managed by realligning TA: What is your experience of implanting phakic
the IPCL IOLs in ectasia? Do you perform adjunctive procedure
(C3R/INTACS) with the same?
d: Ant subcapsular opacification .... Manged by
wait and Watch and remove IPCL and do Refractive lens MSS: We routinely perform corneal collagen cross
Exchange linking with INTACS for moderate to high keratoconus.
Patients with stable keratoconus after CXL are good
e: Angle closure ..... Never experienced candidates for phakic IOL to correct moderate to high
SK: In our series of 500 odd eyes, we have seen refractive error. But if asymmetry of cone is high Phakic ICL
cataract formation (2 eyes: managing conservatively), might not give good quality of vision.
transient postoperative IOP rise (4 eyes, managed medical
therapy short duration only), traumatic dislocation (1 DR: Once the keratoconus is stable because of cross
eye: referred to retinal expert), retinal detachment (1 eye; linking or ageing and if it is a centered cone, I implant toric
operated vitreoretinal surgery) and invert vault (1 eye; ICL. Prior explanation to patient about residual refractive
managed by flipping over the ICL the next day). error is important.

TA: Recent publications report the successful If Decentered cone, center it with Intacs, stabilise the
implantation of ICLs in ACD < 2.8 mm. Does your cornea with CXL ( same sitting) & if still significant residual
experience support this? What is your cutoff for AC refractive error implant toric ICL after a year.
depth?
RK: Have performed IPCL after C3R successfully.
MSS: Anterior-chamber depth is crucial factor in SK: We have operated 2-3 eyes with stable
determining the success of ICL. The recommended depth keratoconus. It is always better to stabilize progression
is 2.8 mm, and I think 2.7 mm is the minimum depth at in keratoconus and other ectasias before proceeding
which I’d feel comfortable. We have done some cases with for a permanent refractive procedure. Stabilization with
2.7 mm ACD and they did well after surgery. the aid of C3R, careful monitoring of topography and
refractive correction over 1 year should be followed by
DR: My cutoff is 2.75 mm & I strictly adhere to this. this procedure. In our cases, though the refractive error did
RK: I would play safe with 2.8. not get corrected completely, but ICL implantation helped
SK: We have some experience of implanting ICL in the patient in achieving a better BCVA with the aid of
ACD < 2.8mm. Though one should always be cautious spectacles/ CL.
in such cases, we have implanted ICL in over-enthusiatic
patients who are not fit for keratorefractive surgeries, when TA: Is there any role for implanting phakic IOLs
ACD is borderline and gonioscopy shows open angles in candidates with low myopia where keratorefractive
without an element of occludability or pigment dispersion. surgery is not contraindicated?
These patients have done well over time. Based on this
experience we may implant pIOL till a lower cutoff limit MSS: Keratorefractive surgery is the first choice
of 2.6mm. as far as low to moderate myopia is concerned. Invasive
procedure should not be the first choice.
TA: In case of very high refractive error not
amenable to correction by ICL alone, would you prefer DR: No. Laser vision correction by virtue of it
to combine ICL with corneal refractive procedures remaining an extra ocular procedure will always be my
(Bioptics) or perform Refractive lens exchange? first choice. In low myopia, with modern laser systems
& aspheric ablation profiles there is no loss in quality of
MSS: We prefer bioptics for very high refractive vision also.
errors as refractive lens exchange has a higher risk of retinal
detachment. Extreme dry eyes maybe a relative reason for
preferring Phakic IOLs over laser vision correction even in
DR: Never perform clear lens extraction in high low myopia.
myopia due to severe retinal complications. In extreme
hyperopia clear lens extraction is an option. RK: It’s a personal choice but Cost is a deterring
factor.

16 l DOS Times - Vol. 20, No. 7 January, 2015

Refractive Surgery

SK: In cases of myopic astigmatism, the keratorefractive TA: What is the future of phakic IOLs? Will
surgery is not contraindicated. However results of LASIK are its indications widen as we continue to have greater
often less predictable in eyes with myopic astigmatism than experience with them?
in eyes with myopia. In these cases we prefer to implant
Toric pIOL compared to performing LASIK. MSS: Phakic IOLs over a period of time have evolved
to become safer and easier to implant. In future we can
TA: Do you feel any difference with the results expand its usage in other indications like add on piggy
with newer models of ICL? Is the postoperative vaulting back lenses and to correct post corneal transplant refractive
similar to the previous models? error and astigmatism.

MSS: We have experience of Centraflow and IPCL DR: They will remain an integral part of the refractive
amongst the newer models. The results are by far the same. surgeon’s armamentarium complementing laser vision
In Centraflow Peripheral iridotomy is not required. correction. With the development of Multifocal lenses, one
size fits all ( no need to vary sizing according to anterior
DR: Vaulting is similar to older models. Less pigment segment dimensions) & preloaded lenses there usage may
dispersal since PI is avoided. increase.

Refractive correction is comparable. If the price of these lenses is brought down, we will
RK: The Vaulting is the same and IOP control better be able to offer it to more patients.
with newer model.
SK: The new ICL with the CentraFLOW design (ICL RK: Yes, the future is very Bright and with newer
V4c) provides similar results as its predecessors without this materials and wide power range and Predictable results, it
technology for the correction of moderate to high myopia may become the treatment of choice in refractive correction.
and maintenance of safe IOP levels without iridotomy.The
vaulting remains similar to V4b model. SK: Looking at the journey of ICLs, their use has
definitely widened over the years. With established data
TA: What is the postoperative regimen and which on safety, predictability and efficacy of ICLs, other than
tests do you perform at each follow up visit? being used in myopia, hyperopia, myopic astigmatism,
they are now being combined with higher refractive errors
MSS: We give topical antobiotic and steriod eye in accordance with bioptics, used in stable keratoconus,
drops and taper steroids in 4 weeks time period. We do pediatric myopic amblyopias etc.
refraction, NCT, vault measurement on ASOCT for first
three visits at 1 day, 1 week and 3 weeks postoperative. The newer indications include: Stable keratoconus,
pediatric population with unilateral anisometropic
DR: - 4th generation fluoroquinolones qid for 1 week amblyopia
- 0.5% timolol bd for 1 week
- Loteprednol qid for 1 week The percentage of eyes with uncorrected visual acuity
- Non preserved lubricants if necessary (UCVA) of 20/20 or better at 12 months postoperative was
Complete eye examination at postop day 1, 6th not significantly different between the two groups. Phakic
week and yearly thereafter. IOL surgery was safer than excimer laser surgical correction
RK: a: Vision for moderate to high myopia as it results in significantly
b: IOP less loss of best spectacle corrected visual acuity (BSCVA)
c: Slit Lamp examination to check vaulting and to at 12 months postoperatively. However there is a low risk
see any other reaction of developing early cataract with phakic IOLs. Phakic IOL
SK: Postoperatively, we prescribe the patients surgery appears to result in better contrast sensitivity than
a regimen comprising of topical steroids 6/d (tapered excimer laser correction for moderate to high myopia.
over 3-4 weeks), topical cycloplegics tid (3 weeks) and Phakic IOL surgery also scored more highly on patient
topical antibiotics qid (3 weeks). It is always safe to assess satisfaction/preference questionnaires.
intraocular pressure in these patients 1-2 hours after surgery
and the next post-operative day by non-contact means. DOS Correspondent
Usual investigations comprise of UCVA, BCVA, Tarun Arora MD, DNB, FICS
refraction, IOP, slit lamp biomicroscopy (anterior chamber
reaction, pigment dispersion, vaulting etc.), ASOCT (for ICL Senior Resident,
vault) and stereopsis assessment. Cornea Lens and Refractive Services,
Dr Rajendra Prasad Centre for Ophthalmic Sciences,
All India Institute of Medical Sciences, New Delhi.

www. dosonline.org l 17

RefracRtievfreactSivue Srugregerryy

Trifocal IOLs

Tarun Arora
MD, DNB, FICO

Tarun Arora MD, DNB, FICO, Vijay Kumar Sharma MS,
Rajesh Sinha MD, DNB, FRCS, Jeewan S. Titiyal MD

Cornea, Lens and Refractive Surgery Services, Dr. Rajendra Prasad Centre for Ophthalmic Sciences,
All India Institute of Medical Sciences, New Delhi

Multifocal lenses were introduced 25 years back to primary foci. When the pupil aperture becomes larger, the
achieve spectacle independence after cataract surgery. peripheral steps are progressively exposed with increasing
Although most studies reported good results in distance amounts of light dedicated to distance vision and less light
and near visual outcomes; poor scores were obtained to the near and intermediate focal points. (Figure 2). This
for intermediate vision1,2. Intermediate vision relates to gradual decrease of the step height from center to periphery
activities such as computer work, car driving (instrument has been shown to reduce halos, which are generated by
panel), music playing (musical chart), etc. In these activities defocused light under dim conditions. The percentage of
for which good uncorrected vision is required for distances lost energy for typical bifocal diffractive IOLs is 18%–20%,
comprising between 60 and 80 cm, glasses may be required while it is approximately 15% for the FineVision IOL. This
despite satisfactory near and distance uncorrected vision. is due to accumulation of the energy from the second order
FineVision IOL (PhysIOL) of the diffractive pattern for the intermediate vision (+1.75
A pioneering solution was proposed in 2010 with the D) to the energy from the first order of the diffractive
introduction of the first trifocal diffractive lens (FineVision, pattern for the near vision (+3.50 D). Thus, the selection
Physiol; Belgium)3. This 25% hydrophilic acrylic IOL of this double-diffractive pattern saves energy which is
(Figure 1) has, in addition to a near foci (+3.50 D), a used for near vision and if lost would increase the risk of
foci for intermediate vision (+1.75 D) to provide treated blurred image. The light scattering on the step edges can
patients with a full range of correction. It has four closed be decreased by their smoothing. Theoretically this can be
haptics and is made of hydrophilic methacrylate with 25% done by adding a mathematical smoothing function, called
water content at the equilibrium. It has a biconvex and “convolution.”
aspheric optic allowing for spherical aberrations of −0.11 PhysIOL in recent months announced changes to the
μm at 5.0 mm aperture. Its optic diameter is 6.15 mm, and original FineVision lens, and it has introduced two new
its total diameter 10.75 mm. It comes in the range of +10 trifocal lenses, including the toric version of its trifocal
D to +35 D (0.5 D steps).The haptic angulation is 5°. An IOL. The company’s original trifocal IOL was renamed as
asymmetric distribution of energy among the three foci the Micro FineVision (Micro F) and given a wider range of
(near, intermediate, and far) allows for dominant distance spherical powers, but it has the same shape, size and haptic
vision, improved intermediate vision, and non-impacted configuration as the initial lens.
near vision. The IOL is based on a fully diffractive optic AT LISA trifocal IOL
with gradual attenuation of the diffractive step height A second diffractive IOL model (+3.33 D near add and
throughout the entire optic, resulting in a continuous +1.66 D intermediate add at the IOL plane) was introduced
change of the light energy distribution directed to the three

www. dosonline.org l 19

Refractive Surgery: Trifocal IOLs

Figure 2: Relationship of light distribution vs pupil
diameter for trifocal IOLs

Figure 1: Fine Vision IOL: First trifocal IOL to be
introduced in practice

later in 2012 (AT LISA tri 839MP, Zeiss; Germany). AT LISA Figure 3: AT LISA trifocal IOL
trifocal IOL (Figure 3) reduces light loss to an average of
14.3 percent, although the mechanisms by which it does so Clinical results with trifocal IOL
are unclear. The IOL optic distributes light energy among In optical bench tests, Costa et al4 measured the optical
the 3 focal points within the central 4.34-mm optical zone. performance at different focal points and aperture
Beyond the 4.34-mm zone, the AT LISA tri 839MP IOL’s sizes of the AT LISA trifocal IOL and two models of the
diffractive optic structure is exclusively bifocal (near and bifocal AcrySof ReSTOR (Alcon, Fort Worth, Texas). The
distance vision). Bench tests have found that with a 2.0 mm researchers reported that the AT LISA had the highest
pupil the lens transmits 50 percent of the usable light to the modulation transfer function (MTF) value at the -1.5 D
distance focus, 30 percent to intermediate and 20 percent focal point at all apertures. The ReSTOR SV25T0 (+2.5 D
to near, according to Zeiss. The proportion of light energy add) had the highest MTF at the 0.0 D focal point; ReSTOR
sent to the intermediate focal point is virtually the same SN6AD1 (+3.0 D add) was best at -2.5 D and -3.0 D focal
at all pupil sizes, about 30 percent. At larger pupil sizes, points, if the aperture was 3.0 mm. When the aperture
the bifocal periphery makes the IOL strongly distance- widened to 4.5 mm, the AT LISA had the highest MTF value
dominant; nearly 60 percent of light goes to distance vision at the -3.0 mm focal point.
with a 6 mm “pupil.” Because the proportion sent to the Mojzis et al5 found that presbyopic patients who underwent
intermediate focal point remains at about 30 percent, the bilateral refractive lens exchange and implantation with
fraction of light devoted to near vision plummets to well the AT LISA trifocal IOL experienced improved near,
under 10 percent. The lens has an aspheric aberration intermediate and distance vision six months after surgery
correcting design with an overall diameter of 11.0 mm, compared to preoperatively. Postoperative refractive
and a 6-mm optic zone diameter. The IOL is available from status was within the range of +1.00 to -1.00 diopter in
+0.0 to+30.0 D in steps of 0.50 D and it includes a UV
blocker.

20 l DOS Times - Vol. 20, No. 7 January, 2015

Refractive Surgery

all 30 patients, and total internal aberrations decreased toric lens does not yet have the CE mark for marketing
significantly. in Europe. When approval comes, this IOL will be able
A recently published study by Marques et al6 compared to correct greater amounts of astigmatism, from +1.0
the visual outcomes after cataract surgery with bilateral to +6.0 D, than the AT LISA trifocal toric, which is
implantation of either Finevision Micro F IOL or an AT currently available with cylinder powers of +1.0 to
Lisa tri 839 MP IOL. Both trifocal IOL models provided +4.0 D.
excellent distance, intermediate, and near visual outcomes. Conclusion
Monocular DCIVA and DCNVA appeared slightly better Trifocality maintains distance and near vision performance
with Finevision Micro F IOL. Predictability of the refractive while adding a third foci for improving outcomes for
results and optical performance were excellent, and all intermediate vision. Binocular implantation of trifocal
patients achieved spectacle independence. IOLs produces good distance visual acuity and near and
Other comparisons between the two Trifocal IOLs intermediate visual function.
• The FineVision has four closed-loop haptics (which in References

the second generation are being replaced by two pairs 1. Mesci C, Erbil H, Ozdoker L, et al. Visual acuity and contrast
of open-loop haptics), whereas the AT LISA has a plate sensitivity function after accommodative and multifocal intraocular
haptic design. lens implantation. Eur J Ophthalmol. 2010;20:90–100
• Although both IOLs are injectable, the pre-implantation
steps differ. The AT LISA trifocal and its toric counterpart 2. Cochener B, Lafuma A, Khoshnood B, et al. Comparison of outcomes
are sold already folded and loaded into a cartridge, with multifocal intraocular lenses: a meta-analysis. Clin Ophthalmol.
which the surgeon attaches to an injector. However, 2011;5:45–56.
the FineVision must be manually folded and then
loaded into an injector before insertion through a 1.8 3. Gatinel D, Pagnoulle C, Houbrechts Y, et al. Design and qualification
mm or 2.0 mm incision. of a diffractive trifocal optical profile for intraocular lenses. J Cataract
• Unlike the AT LISA trifocal’s toric version, the Refract Surg. 2011; 37:2060-67.
FineVision Toric cannot be injected through a 1.8
mm wound. It will require 2.0 mm when it becomes 4. Madrid-Costa D, Ruiz-Alcocer J, Ferrer-Blasco T, et al. Optical
available commercially. Quality Differences Between Three Multifocal Intraocular Lenses:
• A toric version of the Zeiss trifocal IOL, the AT LISA tri Bifocal Low Add, Bifocal Moderate Add, and Trifocal. J Refract Surg.
toric 939M, received approval last year for European 2013;29:749-54.
marketing, which made it the first toric trifocal available
to international cataract surgeons. FineVision’s trifocal 5. Mojzis P, Peña-García P, Liehneova I, et al. Outcomes of a new
diffractive trifocal intraocular lens. J Cataract Refract Surg.
2014;40:60-69.

6. Marques EF, Ferreira TB.Comparison of visual outcomes of 2
diffractive trifocal intraocular lenses. J Cataract Refract Surg. 2015
Feb;41:354-63.

www. dosonline.org l 21

RefracRtievfreactSivue Srugregerryy

Topography Guided
Kerato-Refractive Surgery

Pooja Bandivadekar
MD

Pooja Bandivadekar MD, Manpreet Kaur MD

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

As the number of patients undergoing LASIK surgery the visual axis2. The point that is closest to this physiologic
increases, we encounter greater number of patients centration point and can be measured by currently available
with atypical corneas that may not strictly confirm to the devices is coaxially sighted corneal light reflex (CSCLR). It
‘ideal’ and yet may not also strictly confirm to the list of is imperative to have the technology to center the ablation
contraindications. Also, patients with decentered ablation profile on the CSCLR (Figure 1).
profile, post-LASIK ectasia, greater angle kappa, partially What is topography-guided LASIK?
cut flaps and post keratoplasty astigmatism may present The two principle elements of topography guided
for visual rehabilitation. With evolving concepts and photoablation are:
technology, it is possible to customize treatment for these (a) Assessment of topography
highly demanding niche cases. We have tried to answer the (b) Centering the ablation on the corneal vertex.
following questions in a lucid manner: In topography guided photoablation, corneal topography
• What is topography guided LASIK? (point to point variation in curvature and refractive power)
• How is it different from other customizations like is used for photoablation in conjunction with the refractive
error of the eye. Secondly, all measurements are centered
Wavefront-guided LASIK/PRK? on the corneal vertex and not on the pupillary center or
• What are the specific indications? geographical corneal center.
Angle kappa and its importance in refractive Different methods are used to evaluate the corneal
surgery topography, each with its own advantages and
Conventional photoablation is centered over the entrance disadvantages. Either a placido-disc reflection of the
pupil. However, the visual axis of the eye (line connecting anterior corneal surface or a Schiemflug-based imaging
the fixation point with the fovea) and the pupillary axis system can be used to obtain the topography maps. The
(line that perpendicularly passes through the entrance pupil placido-disc based device captures upto 22,000 points on
and the center of curvature of the cornea) are essentially the anterior corneal surface, including corneas with scar or
different. The angle between them is called angle kappa. In opacity (Figure 2). The data from this image acquisition is
most patients, the value lies between 5.55 ± 0.13° and 5.62 transferred directly to the excimer laser device for further
± 0.10° in right and left eyes respectively when measured integration and planning. The Schiemflug based device
by the Orbscan II corneal topographer (Bausch and Lomb, captures upto 25,000 true elevation points, including the
USA)1. In 97% of non-hyperopic eyes undergoing refractive posterior corneal surface. The disadvantage of placido-
surgery, a positive angle kappa of 0.5 mm or less was based devices is their inability to capture the central
observed. However, the average angle kappa is greater in corneal data, whereas Schiemflug based devices are
patients with hyperopia. In these patients, centering the unable to capture images in relatively opaque corneas
ablation profile on the geometric center of cornea or on or scarred corneas. For images captured using placido
the pupillary center would result in eccentric ablation. The
ideal physiologic centration point is the corneal intercept of

www. dosonline.org l 23

Refractive Surgery: Topography Guided Kerato-Refractive Surgery

Figure 1: Relation of visual axis to pupillary axis and their geographical intersection on the
cornea. GCC=geometric corneal center; CSCLR= Co-axially sighted corneal light reflex.

disc, 5 point pachymetry needs to be manually entered, • Centering the ablation profile on the corneal vertex
unlike the Schiemflug based device which automatically • Correction of asphericity and choosing the desired
captures the values.These devices also digitally determine
the limbus and pupillometry measurements using infrared optical zone in smaller steps than conventional LASIK.
camera. This helps in correctly identifying the pupil However, the amount of corneal tissue ablated in most
center intraoperatively and then shifting the ablation cases of topography guided treatments is more than the
profile towards the corneal vertex. All this pre-operative conventional wavefront optimized treatments.
information is transferred to the excimer laser software. How is it different from other customizations like
The software integrates refractive error and topography to Wavefront-guided LASIK/PRK?
generate an ablation profile (Figure 3). The profile can be The term ‘customized LASIK/PRK’ is a confusing
mix of myopic and hyperopic ablation zones. It gives the terminology. It includes a plethora of options for catering
surgeon the option to choose the optical zone as well as the to the specific demands of patients who may or may not be
transitional zone in 0.1mm steps. suitable for conventional wavefront-optimized LASIK/PRK.
Complete refractive error or a part of it can be corrected Wavefront guided, topography-guided and asphericity-
based on pachymetry or surgeon preference. This strategy guided treatments fall under the broad title of Customized
is useful in cases of irregular corneas where smoothening of LASIK.
anterior corneal surface is a priority, rather than correction Wavefront guided treatments center all their measurements
of refractive error. on the entrance pupil. The size and the location of pupil
In short, topo-guided treatments offer a basket of choices: limit the area that can be measured. The wavefront is also
• Smoothening of anterior corneal surface with or affected by accommodation and opacity in cornea or the

without correction of refractive error

24 l DOS Times - Vol. 20, No. 7 January, 2015

Refractive Surgery

Figure 2: The Placido-disc based Alcon Topolyzer ® Figure 3: Ablation profile of a patient with post-
keratoplasty irregular astigmatism (A): for correction of
lens3. The aberrometer often fails to capture accurate data topography only. (B): for correction of topography with
in highly aberrated eyes.
The ablation strategy employed by the Wavefront guided refractive error as well.
and topography-guided technologies differs significantly.
Consider a heap of soil with a pit beside it. The aim of 70% data accurately captured along with the limbus). The
the treatment would be to get both to the same level. quality of image is affected by the tear film as well. So
The wavefront guided treatment would work by ablating image acquisition in a large number of indicated patients
the heap of soil to the level of the pit. However, the may be difficult. Two stage procedures may have to be
topography guided treatment would ablate the heap but done when one desires correction of the refractive error
raise the bottom of the pit to get both to the same level. along with regularizing the corneal surface. The first step
So you have an area that undergoes myopic ablation (heap would smoothen the anterior corneal surface and at the
of soil) and a mid-peripheral area that undergoes ablation same time may induce refractive errors. The second stage
to induced steepening in the center similar to hyperopic surgery would correct the residual refractive error.
ablation (raising the bottom of the pit). The wavefront takes What are the specific indications?
into account the aberrations of the entire eye, including A Treatment of Regular Cornea
the lens. The lens may induce significant aberrations which B Treatment of Irregular Cornea
are corrected at the corneal level during ablation. A lot of • Post-LASIK Complications- Decentered ablation
surgeons disagree to this policy as the aberration status
of the eye would change again when the patient would profile, small optic zone, button-holes or vertical
undergo a lens-based surgery at a later date. gas breakthrough with irregular flaps, post-LASIK
The image acquisition in highly irregular corneas may be ectasia
difficult for the current generation of topography devices. • Post-RK cases
Also, multiple images may be needed (more than the • Post-keratoplasty refractive error correction4
average 8) to get images of sufficient quality (more than • Regularization of cornea in keratoconus (Combined
with Collagen cross linking)5,6
As the experience with topography guided laser increases,
customization is increasingly being used in routine
photoablative procedures especially hyperopic ablation
where the expected angle kappa is large7. In cases with
previously operated LASIK or RK, symptoms like star-burst,
haloes or glare may be alleviated by using topo-guided LASIK.
Holland et al, in their study of post-LASIK ectasia treated 12
eyes with topography guided laser and an UDVA of 20/40
or better was achieved in 71 % eyes compared with 12%
in the pre-operative period, with ≥ 2 lines gain in vision in
53 % eyes8. Chen et al documented an improvement in the
irregularity index of cornea following topography guided
ablation. Spadea reported an improvement in the spherical
equivalent and a decrease in refractive astigmatism
following post-keratoplasty Topo-guided treatment with

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Refractive Surgery: Topography Guided Kerato-Refractive Surgery

CXL. However, complications in cases with highly Interactive Programmed Topographic Ablation (CIPTAmax;
aberrated corneas undergoing photoablative treatment are iVis Technology, Taranto, Italy).
not yet well documented, due to small sample size of most
studies as well as short term follow-up. A word of caution References
is mandated in the indiscriminate use of topography guided
LASIK / PRK. 1. Moshirfar M, Hoggan RN, Muthappan V. Angle Kappa and its
The role of epithelial remodeling to compensate for the importance in refractive surgery. Oman J Ophthalmol. 2013;6:151-
irregularities in stroma is still being researched. Epithelial 58.
remodeling contributes a great deal to the eventual
refractive outcome. Trans-epithelial phototherapeutic 2. Pande M, Hillman JS. Optical zone centration in keratorefractive
keratectomy aims at neutralizing this epithelial remodeling surgery. Entrance pupil center, visual axis, coaxially sighted corneal
and then reshaping the underlying stroma9. reflex, or geometric corneal center? Ophthalmology. 1993;100:1230-
Planning software and treating platforms 37.
A range of planning software and topography-guided
ablation platforms are commercially available. Topography- 3. Stojanovic A, Chen S, Chen X, et al. One-Step Transepithelial
guided customized ablation treatment (T-CAT) planning Topography-Guided Ablation in the Treatment of Myopic
software with ALLEGRETTO WAVE Eye-Q Excimer laser Astigmatism. PLoS ONE. 2013;8(6).
platform (Alcon Laboratories Inc, Ft Worth, Texas, USA)
has recently received the U.S. FDA approval, and has been 4. Feizi S, Zare M. Current Approaches for Management of
approved in Europe since 2003. Other platforms currently Postpenetrating Keratoplasty Astigmatism. J Ophthalmol. 2011.
available are the CRS-Master planning software (Carl Zeiss
Meditec, Jena, Germany), Nidek Advanced Vision Excimer 5. Shetty R, D’Souza S, Srivastava S, Ashwini R. Topography-guided
(NAVEX; Nidek, Gamagori, Japan), and the Corneal custom ablation treatment for treatment of keratoconus. Indian J
Ophthalmol. 2013;8:445-50.

6. Li N, Peng X-J, Fan Z-J. Progress of corneal collagen cross-linking
combined with refractive surgery. Int J Ophthalmol. 2014;7:157-62.

7. Kanellopoulos AJ. Topography-guided hyperopic and hyperopic
astigmatism femtosecond laser-assisted LASIK: long-term experience
with the 400 Hz eye-Q excimer platform. Clin Ophthalmol Auckl
NZ. 2012;6:895-901.

8. Holland S, Lin DTC, Tan JCH. Topography-guided laser refractive
surgery. Curr Opin Ophthalmol. 2013;4:302-09.

9. De Rosa G, Boccia R, Santamaria C, Fabbozzi L, De Rosa L, Lanza M.
Customized photorefractive keratectomy to correct high ametropia
after penetrating keratoplasty: A pilot study. J Optom. 2014.

26 l DOS Times - Vol. 20, No. 7 January, 2015

RefracRtievfreactSivue Srugregerryy

LASIK Xtra: What is the
Extra Benefit?
Shilpi Diwan
MS

Shilpi Diwan MS, Ritika Sachdev MS, Mahipal Singh Sachdev MD
Cornea and Refractive Services, Centre for Sight Group of Eye Hospitals, New Delhi

One of the most devastating complications of LASIK is In 2009 Kanellopoulos and colleagues introduced the
Post LASIK corneal Ectasia. This entity was described concept of concurrent corneal collagen cross linking in
first by Seiler et al.1 as progressive stromal thinning, a conventional LASIK procedure which later came to be
corneal steepening, decreased uncorrected distance known as LASIK Xtra. It seems to be addressing both the
visual acuity (UDVA), and corrected distance visual acuity above mentioned complications of LASIK. Concurrent
(CDVA). Since then several guidelines have been laid for cross linking enhances the biomechanical strength of
the refractive surgeons to prevent the occurrence of Post corneas undergoing Excimer ablation, thereby reducing the
LASIK ectasia. Randleman et al.2 developed a scale, Ectasia possibility of post LASIK ectasia and also promotes the long
Risk Score System (ERSS), which includes preoperative term stability of the refractive correction.
parameters, to predict the chances of post-LASIK ectasia. Candidates for LASIK Xtra
This scale includes risk factors such as low stromal bed The procedure is indicated in an individual undergoing
thickness, low preoperative corneal thickness, abnormal refractive correction using Excimer ablation, having higher
preoperative corneal topography, young age and high risk for development of Post LASIK Ectasia or marked
refractive correction. However, despite the most advanced regression.
preoperative evaluation techniques, there have been reports These include:
of cases developing Post LASIK ectasia, even in the absence • High Myopes
of any preoperative risk factors leaving the refractive • Hyperopic LASIK
surgeons faced with the challenge of management of post • High Astigmatic refractive errors
LASIK ectasia. • Those with borderline corneal thickness
Other bothersome sequela of LASIK is regression of • Those with topographic asymmetry or irregularities
refractive correction. It is known to be higher with the use • Younger patient age
of certain types of excimer machines, ablation patterns, • Those with family history of Keratoconus
optical and transition zone diameters and patient age. • Those with Atopic Dermatitis
Despite of improvements in the Excimer beam profile and • Those with Chronic ocular allergy
alterations in treatment zone dimensions, regression still LASIK Xtra- Procedure
manages to annoy the refractive surgeons. As in a convention LASIK procedure, after lifting the corneal
Management of Post LASIK Ectasia traditionally involved flap and performing the refractive correction, the LASIK
Spectacle correction, Rigid Contact Lenses, Intra Corneal flap is folded over itself in order to prevent Riboflavin
Ring segments and ultimately Keratoplasty, Penetrating/ absorption by the flap (Figure 1). Then a single instillation
Anterior Lamellar, in the most advanced cases. In 1998, of Avedro’s Riboflavin formulation, Vibex XtraTM is done
the introduction of Corneal Collagen Crosslinking (CXL)
revolutionised the management of corneal ectatic disorders
including progressive Post LASIK ectasia. It has been
proven that CXL induces corneal biomechanical changes
causing corneal stiffening thereby arresting/ slowing the
progression of corneal ectasia.

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Refractive Surgery: LASIK Xtra: What is the Extra Benefit?

Figure 1: Riboflavin instilled over the stromal bed Figure 2: Avedro KXL System

over the exposed stromal bed and carefully spread over and can be noted even 5 years after hyperopic LASIK
the stromal bed with the help of irrigating canula. This procedure. Therefore, hyperopic LASIK Xtra, by reinforcing
soaking is continued for 60 seconds and then the flap is the biomechanical behaviour of the cornea, counteracts
repositioned into place. Residual Riboflavin is irrigated the intrinsic progressive flattening of the hyperopic LASIK
and next, very high fluence cross linking is carried out corneas and therefore offers higher stability and the ability
over the flap. Whereas the standard CXL procedure uses to treat higher degrees of hyperopia with LASIK Xtra.
classic Dresden’s protocol, that is 3MW/cm2 UV fluence at Discussion
the average wavelength of 370nm, Avedro LASIK Xtra, KXL Kanellopoulos and colleagues studied LASIK Xtra in
System (Figure 2) involves the use of higher fluence UV Hyperopic corrections and concluded that Hyperopic
irradiation i.e. 30 MW/cm2, for 80 seconds (total energy LASIK Xtra, by reinforcing the biomechanical behaviour of
2.4 J/cm2). Prior to introduction of Avedro LASIK Xtra, the cornea, counteracts the intrinsic progressive flattening
KXL System, concurrent cross linking was done with a UV of the hyperopic LASIK corneas and therefore offers higher
fluence of 10 MW/cm2.3 stability and the provides for treatment of higher degrees of
Vibex XtraTM is 0.1% Riboflavine diluted in saline instead hyperopia3.
of Dextran. A significant incidence of Diffuse Lamellar Kanellopoulos studied Forty-three consecutive LASIK cases
Keratitis (DLK) was observed in initial cases of concurrent treated with femtosecond laser flap and the WaveLight
cross linking using standard 0.1% Riboflavine stabilised excimer and subsequently cross linked with UV-A
with 10% Dextran. Studied proved that Dextran which was irradiation4. The eyes were evaluated perioperatively for
left under the LASIK flap led to DLK, hence the Riboflavine uncorrected visual acuity, best corrected spectacle visual
used for LASIK Xtra, was diluted with saline instead of acuity, refraction, keratometry, topography, total and flap
Dextran. pachymetry, corneal optical coherence tomography, and
The rationale of treatment using a LASIK flap (as opposed endothelial cell count. Mean follow-up duration was 3.5
to irradiating the riboflavin-soaked stroma) is to reduce (range 1.0-4.5) years. He concluded that prophylactic
stromal exposure time and the risk of flap dehydration4. collagen cross-linking for high-risk LASIK cases was a safe
LASIK flap is prevented from exposure to Riboflavin as this and effective adjunctive treatment for refractive regression
would lead to partial absorption of the UV radiation and and potential ectasia.
hence suboptimal UV irradiation induced cross linking in
the residual stromal bed, which is the most important zone
contributing to corneal biomechanical stability. Also the
flap would have only 60-70 micron thickness of the stromal
tissue (depending on the planned flap thickness) and cross
linking in such thin layer of stromal tissue may lead to flap
shrinkage which might compromise the refractive outcome.
Hyperopic LASIK has an intrinsic biomechanical response,
which results in progressive flattening of the central cornea
beginning approximately 4-6 months after the procedure

28 l DOS Times - Vol. 20, No. 7 January, 2015

Refractive Surgery

Kanellopoulos and colleagues conducted a study on 165 LASIK-CXL eyes. The demarcation line (mean depth 200.04
consecutive eye posted for Myopic LASIK correction5. μm ± 27.01 [SD]; range 178 to 278 μm) was present in
They compared 73 eyes undergoing standard LASIK with 95.8% eyes. They concluded that combined LASIK-CXL
concurrent high fluence CXL with 82 eyes undergoing was safe, causing insignificant corneal biomechanical and
standard LASIK alone. Both the groups were followed upto morphologic changes similar to those with CXL treatment
1 year post operatively and manifest refractive spherical only.
equivalent (MRSE), refractive astigmatism, visual acuity, Celik and group conducted a study in which patients
corneal keratometry, and endothelial cell counts were underwent LASIK with concurrent accelerated CXL in
evaluated. They concluded that application of prophylactic 1 eye and LASIK only in the fellow eye to treat myopia
CXL concurrently with myopic LASIK surgery appeared to be or myopic astigmatism. The follow-up was 12 months9.
a safe procedure which contributes to improved refractive The attempted correction (spherical equivalent) ranged
and keratometric stability compared to standard LASIK. This from -5.00 to -8.50 diopters (D) in the LASIK-CXL group
was evidenced by slightly regressing keratometric stability and from -3.00 to -7.25 D in the LASIK-only group. Main
plots in the standard LASIK group as compared to stable outcome measures were manifest refraction, uncorrected
plots in the LASIK CXL group. (UDVA) and corrected (CDVA) distance visual acuities, and
Mazzotta et al, performed in vivo confocal microscopy the endothelial cell count. They found that at the 12-month
in a case of sequential accelerated CXL and followed up follow-up, the LASIK-CXL group had a UDVA and manifest
the patients unto 6 months post procedure6. The study refraction equal to or better than those in the LASIK-only
revealed that Epithelial basal cells showed an immediate group. No eye lost 1 or more lines of CDVA at the final
slight damage related to a direct cytotoxic effect of UV-A visit. The endothelial cell loss in the LASIK-CXL eye was
irradiation; however, the epithelium appeared normal not greater than in the fellow eye. No side effects were
in the first month after treatment. During the follow-up, associated with either procedure. They concluded that
corneal edema disappeared gradually and keratocyte Laser in situ keratomileusis with accelerated CXL appears
repopulation was complete at the 6th month. No changes to be a promising modality for future applications to
in the density of the extracellular matrix, were recorded at prevent corneal ectasia after LASIK treatment. The results in
the 6th month. Endothelial cell counts did not show ant this pilot series suggested that evaluation of a larger study
significant deterioration during the 6 month follow-up. The cohort is warranted.
study proved the safety of this procedure. In conclusion it can be stated that LASIK with prophylactic
Kanellopoulos et al. studied the possible topographic concurrent collagen cross linking is a safe procedure
epithelial profile thickness changes (remodelling) after high which enhances the post ablation biomechanical stability
myopic femtosecond laser in situ keratomileusis (LASIK) of cornea thereby providing a longer refractive and
with concurrent prophylactic high fluence cross-linking in keratometric stability both in myopic and hyperopic eyes.
comparison to standard Femtosecond LASIK7. They studied It does not have any deteriorating effect on cornealstromal
3 dimensional epithelial thickness distribution 6 months keratocytes or the endothelial cells. However issues such
post operatively using clinical spectral domain Anterior as the effect of concurrent cross linking on the visual acuity,
Segment Optical Coherence Tomography in matched induced aberrations, effect on contrast sensitivity require to
high myopic correction subgroups. It was concluded that be studied in detail. Further studies with a larger cohort and
application of prophylactic CXL concurrently with high a longer followup period are recommended.
myopic LASIK operation results in a statistically significant References
reduced epithelial increase in comparison with stand-
alone LASIK and this difference may correlate with higher 1. T. Seiler, K. Koufala, and G. Richter. Iatrogenic keratectasia after laser
regression rates and/or may depict increased biomechanical in situ keratomileusis. Journal of Refractive Surgery 1998;14:312–
instability in stand-alone LASIK. 17.
Tomita et al from Shinagawa LASIK centre, Tokyo in their
study compared eyes which underwent LASIK XtraTM to 2. Mi S, Dooley EP, Albon J, Boulton ME, Meek KM, Kamma-Lorger
those undergoing LASIK only8. They found changes in the CS. Adhesion of laser in situ keratomileusis-like flaps in the cornea:
corneal stroma cells similar to the changes in conventional Effects of crosslinking, stromal fibroblasts, and cytokine treatment. J
CXL using confocal microscope examination. No significant Cataract Refract Surg. 2011;37:166–72.
differences were found in UDVA, CDVA, MRSE, ECD,
dynamic bidirectional applanation readings (eg, CH, CRF, 3. Anastasios John Kanellopoulos, Gregory J Pamel. Review of current
KMI), or 37 additional studied parameters, between the indications for combined very high fluence collagen cross-linking
2 groups. Increased hyper reflectivity and a demarcation and laser in situ keratomileusis surgery. Indian J Ophthalmol.
line similar to that seen after CXL were observed in the 2013;61:430–32.

4. Anastasios John Kanellopoulos. Long-term safety and efficacy
follow-up of prophylactic higher fluence collagen cross-linking in
high myopic laser-assisted in situ keratomileusis. Clin Ophthalmol.
2012;6:1125–30.

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Refractive Surgery: LASIK Xtra: What is the Extra Benefit?

5. Anastasios John Kanellopoulos, Costas Karabatsas. Comparison 8. Tomita M, Yoshida Y, Yamamoto Y, Mita M, Waring G 4th. In
of prophylactic higher fluence corneal cross-linking to control, in vivo confocal laser microscopy of morphologic changes after
myopic LASIK, one year results. Clin Ophthalmol. 2014;8:2373–81. simultaneous LASIK and accelerated collagen crosslinking for
myopia: one-year results.J Cataract Refract Surg. 2014;40:981-90.
6. Cosimo Mazzotta, Angelo Balestrazzi, Claudio Traversi, Stefano
Caragiuli, and Aldo Caporossib. In vivo Confocal Microscopy 9. Celik HU1, Alagöz N, Yildirim Y, Agca A, Marshall J, Demirok A,
Report after Lasik with Sequential Accelerated Corneal Collagen Yilmaz OF. Accelerated corneal crosslinking concurrent with laser
Cross-Linking Treatment. Case Rep Ophthalmol. 2014; 5:125–31. in situ keratomileusis. JCataract Refract Surg. 2012;38:1424-31.

7. Kanellopoulos AJ, Asimellis G. Epithelial remodeling after
femtosecond laser-assisted high myopic LASIK: comparison of stand-
alone with LASIK combined with prophylactic high-fluence cross-
linking.Cornea. 2014;33:463-9.

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30 l DOS Times - Vol. 20, No. 7 January, 2015

Four Aces of Refractive Surgery: Aberrations, ReDfraiactgivne oSusrtgiecrsy
Aberrometers, Applications and Advances
Maneck Darius Nicholson
DNB

Maneck Darius Nicholson DNB, Vishal Arora MD, Natasha Pahuja DOMS, Rohit Shetty DNB, FRCS
Narayana Nethralaya, Bangalore, Karnataka

Very little attention was paid to the optical properties aberrations (dispersion) are traditionally divided into
of the eye prior to the advent of wavefront guided longitudinal and transverse. Chromatic aberrations
laser vision correction. It is well known that the normal limit retinal image quality because the real world is
human eye suffers from many aberrations, which cause polychromatic.
degradation of visual quality. Visual acuity is limited by Monochromatic aberrations are of two basic types of
diffraction, aberrations and photoreceptor density. Apart aberrations. Lower order and higher order aberrations.
from these limitations, a number of factors also affect visual Zernike expansion of aberrations (Explained later in the
acuity such as refractive error, illumination, contrast and article), are addressed as lower-order aberrations, with the
the location of the retina being stimulated. Zernike radial order n<3, and higher-order aberrations,
Why are aberrations important? with n≥3. This concept of division into lower and higher
For a long time clinicians have beensearching for an answer order is important for the ophthalmologist to understand
as to why a some patients with 20/20 Snellen corrected as the lower-order aberrations (2nd order aberrations,
visual acuity were still unhappy? The answer to this lies in defocus and primary astigmatism) significantly contribute
a cogent understanding of ocular wave front technology. to the total aberrations of the eye (remaining lower-order
Aberrations generated by the eye can be divided forms, piston and tilt, are usually ignored) andcan be easily
intomonochromatic and chromatic aberrations. Chromatic be corrected with glasses or contact lenses. Uncorrected
higher order aberrations (HOA) can be the cause of many

Figure 1: Simulated letter E before and after wavefront guided surgery.

www. dosonline.org l 33

Diagnostics: Four Aces of Refractive Surgery: Aberrations Aberrometers Applications and Advances

Figure 2: iTrace map showing aberrationsoriginating from the internal optical system (beyond posterior surface of
cornea to the retina (Top, Left), cornea (Bottom, Left) and total ocular aberrations (Top, Right). The image on the

right shows the simulated letter E of the same.

symptoms such as double vision, halos, lack of contrastand at the pupillary margin is the only thing that governs image
even compromised far and near vision. The correction of production on the retina. However as pupil size increases
higher order aberrations is believed to result in the so- image quality decreases due to increase in aberration.
called “super vision”, which has sparked the recent interest What do all these terms mean?
in wavefront-guided surgery (Figure 1). Visual quality is measured using certain technical terms.
The understanding of aberrations is important especially in The following explanation provides a simplified overview
refractive surgery. In wavefront guided LASIK the wavefront to have a better understanding of these terms.
analysis is coupled with an excimer laser machine and Point Spread Function (PSF)
excimer laser delivery is in accordance with the patients’ When a point of light passes through an aberrated optical
wavefront profile. In an optical system completely corrected system it causes the beam to spread producing a blur from
using wavefront-guided treatment, image quality is only a point. In such a way, each aberration causes the point of
dependent on diffraction and scattering. light to take on a characteristic appearance when it hits the
This article aims to review the basics of optical principles retina. The PSF of an aberration gives us an idea of what
of aberrations. patients actually see.
What are aberrations? Technically it is the image that an optical system forms of
In simplified terms aberrations can be defined as a point source of light. The PSF for a perfect optical system
imperfections in the human optical system. The ideal is an Airy disc, which is the Fraunhofer diffraction pattern
definition of optical aberrationsis the deviation of the for a circular pupil. The PSF is limited by diffraction and
wavefront that originates from the measured optical system optical aberrations. If the pupil size increases, diffraction
from reference wavefront that comes from an ideal optic decreases but the aberrationswill increase (Figure 3).
system2. PSF and pupil size
These aberrations may originate from any part of the Pupil size is extremely important when analyzing any
human optical system starting from the tear film, the wavefront data. The pupil size must be the same before any
cornea, pupil, lens and even imperfections of the retina. comparison between different maps is performed3.
(Figure 2). The cornea is the main source of ocular Effects of pupil size
aberrations as it dominates the optical power of the eye. 1. There is an increase in blur if either the refractive error
The pupil determines the amount of light entering the eye.
Accommodation produced by the crystalline lens also (LOAs) or pupil size is increased (both are independent
significantly contributes to aberrations. of each other, Figure 4).
The normal human eye is aberrations are minimum at a
pupil diameter of 2.5mm, as at this size diffraction of light

34 l DOS Times - Vol. 20, No. 7 January, 2015

Refractive Surgery

Figure 3: Image on the left shows the PSF of a perfect optical system at different pupil sizes. Image on the right
shows the PSF at different pupil sizes in a typical eye. Note the increase in size of the PSF at increasing pupil size.

Figure 4: Increase in cylinder (LOAs) at increasing pupil size, 2. Pupil size and HOAs are closely related to the depth
reduction in the increase in aberrations with pupils size after of focus. Decrease in pupil size increases the depth of
focus 4But the decrease in pupil size in turn causes
wavefront guided treatment. a reduction in the available light which reduces
visual quality andalso amplifies the adverse effects of
diffraction. It has also been seen that increasing certain
higher order aberrations such as spherical aberration
increases the depth of focus but again decrease visual
quality5.

The magnitude of HOAs that will allow an acceptable
visual quality and the depth of focus while considering the
influence of the pupil size have not been determined and
may vary between subjects.
Strehl Ratio
Strehl ratio is defined by the ratio between the actual
measured PSFpeak height and the PSF peak height of a

Figure 5: Optical Quality Assessment System (OQAS II) used to measure the modulation transfer function
(MTF) and Strehl Ratio. Printout showing the MTF, Strehl ratio contrast at 100 %, 20% and 9% (top).
www. dosonline.org l 35

Diagnostics: Four Aces of Refractive Surgery: Aberrations Aberrometers Applications and Advances

Figure 6: Classification of various aberrometry principles. When the spatial frequency increases, the MTF decreases
because the image contrast is lower than in the object7
diffraction-limited optical system (minimalaberrations). It (Figure 5).
ranges from 0 to 1, where 1 is equal to a diffraction-limited How can we measure these aberrations?
system. The ratio usually decreases as pupil size increases. The purpose of wavefront analyses of the eye is to evaluate
Modulation Transfer Function (MTF) the optical quality of the by measuring the shape of its
MTF is a function that allows for the assessment of the degree wavefront. For this, an aberrometer or wavefront sensor
of detail the human optical system is able to distinguish. is used. All commercial available aberrometers work on
When the quality of an optical system is degraded it is seen similar principle by passingtwo or more parallel beams of
that higher spatial frequencies representing finer details are light through the eye. A method is used to measure the
the first to be affected. MTF measures the contrast loss with extent to which those beams cease to travel in a visually
increasing spatial frequency when transferring an object to optimal trajectory. Complex mathematical formulas then
an image through an aberrated optical system6. predict aberrations based on the altered angle of those
In other words, it evaluates the correlation between contrast beams.
in the image formed by the optical system being measured Original aberrometers were based on the Hartmann
and the original contrast of the scene being observed. The Shack principle. It is a technique developed by Johannes
contrast reduction is greater for high spatial frequencies Hartmann in 1900 and modified by Shack and Platt in
(fine details and image contours). If the image contrast is the late 1960s. Numerous other methodologies and
the same as the object contrast, the MTF is highest i.e. 1. applications have since arisen.The first measurements of
HOAs were conducted by Smirov using a psychophysical
method, in 19618.
All aberrometers have three basic components.
1. An input light source (usually an infrared laser) that

throws light onto the retina.
2. An emerging wavefront represents the optical properties

of the eye.
3. The wavefront passes through a lenslet array made up

of 200 – 1400 lenses depending on the instruments
design. The light passing through individuallenslet
is then focused on a charged coupled device (CCD)
array, which is recorded by a computer.
Aberrometers are classified into three types (Figure 6). The
first type is the outgoing wavefront aberrometer as in the
Hartmann–Shack sensor, 9 the second type is the ingoing

Figure 7: Principle of Hartmann Shack aberrometry.
36 l DOS Times - Vol. 20, No. 7 January, 2015

Refractive Surgery

Figure 8: Image showing the Zywave (Bausch and Lomb), the iDesign (AMO) and IRX3 (Imagine Eye).

retinal imaging aberrometer i.e. Tscherningaberrometer10 The Zwave II aberrometer (Bausch and Lomb, Inc.) is part
and the sequential retinal ray tracing method11. The third of the Zyoptix diagnostic workstation. It gives us the raw
type is the ingoing feed- back aberrometer as used in the image, 2D analysis of the wavefront, variation of refractive
spatially resolved refractometer12 and the optical path power over varying pupillary diameters, higher order point
difference method13. We shall deal with each of these in spread function, 3D wavefront maps, Zernike amplitudes
further detail. and summary with refraction. It provides total wavefront
Hartmann Shack aberrometry analysis up to the 5th order. Assists in establishing a
Principle refractive treatment plan to correct an individual’s particular
A Hartmann-Shack device uses a narrow laser beam that aberration.
is sent along the ocular line of sight into the eye, where it The iDesign is a part of the AMO wavescan studio. It uses a
reflects fromthe retina. This reflection serves as secondary high definition Hartmann Shack sensor and analyzes 1250
source that illuminates the pupillary area from behind. data points. This data is fed to the STAR S4 IR Excimer laser
When a plane or spherical wavefront is projected into before treatment. The iDesign display includes overview
a perfect optical system free of aberrations the returning with eye image, corneal topography, and a Hartmann
wave should be aberration free i.e. plane or spherical. shack image, a custom view with corneal wavefront map,
However if the system has optical aberrations the returning axial power map, elevation map and the eye image, the
wavefront will reflect the aberrations of the system. Zernike coefficient display a wavefront map of total and
The outgoing light is then guided through a set of relay higher order aberrations, the point spread function, and an
lenses that projects the pupil plane onto an array of eye image for the limbus to limbus diameter (Figure 8).
tiny lenses that splits up the wavefront into a number of Limitation
individually focused spots on a charged coupled device 1. Measurement of highly aberrated eyes and small pupil
camera. Because of focal shift, the resulting spot pattern
(figure inset) shows spot displacements compared with the sizes is difficult. As the pupil gets smaller, the number
reference positions. This way, the wavefront slopes are of points diminishes because of the fixed lenslet array
determined for the entire pupil at once14 (Figure 7). density.
Machines using Hartmann Shack aberrometry 2. However fast and uncomplicated (because no moving
(Figure 8) parts are required), the performance of this parallel
1. Zywave method is limited to aberrations that are not too
2. iDesign complicated. To determine the focal shift directly,
3. IRX3 each reference position is allocated a neighborhood
in which the shifted spots are directly associated with
a specific reference position (square grid in figure
inset). For rapidly varying wavefronts with steep

www. dosonline.org l 37

Diagnostics: Four Aces of Refractive Surgery: Aberrations Aberrometers Applications and Advances

Figure 9: Line diagram showing the principle of Figure 10: WaveLight Analyzer Diagnostic
Tscherning aberrometry10. Device (Allegro).

slopes, this can result in focal shifts becoming so large Differential Skiascopy
that spots cross over to neighborhoods belonging to Principle
another reference position. This makes it impossible It is an automated streak retinoscopy done at 360 meridians.
to determine the focal shift in these areas. Crossover It utilizes a principle of skiascopic phase difference for
can be partially prevented by using prefocus lenses that refractive measurements. One slit of light isprojected onto
correct the ocular refraction14. the retina and another detects light reflected back. As these
Tscherning Aberrometry systems continuously rotate around an axis each scans a
Principle meridian of 1 degree.
Contrary to the Hartmann-Shack method, the Tscherning It uses focal shift in a different way, starting from the
aberrometer uses not 1 but a group of laser beams that observation that the retinal image of a light beam coming
enter the eye. These beams are generated using a wide
laser beam passing through a screen with a large number of Figure 11: OPD III scan (NIDEK).
round holes. The lens projects an image of the Tscherning
screen onto the retina, resulting in a spot pattern resembling
a Hartmann-Shack pattern, where again spots are displaced
due to focal shift. The Tscherning method projects a fixed
pattern of spots onto the retina. The retinal image is then
retrieved using a beam splitter and a second lens. The
distortion of the light spots in relation to the light reference
bundle is calculated as the wavefront error. This is then
viewed externally using a CCD camera. The advantage
is that it avoids inaccurate results from media opacities,
which can produce false positives with a Shack-Hartmann
device14 (Figure 9).
Machine using the Tscherning Method
The WaveLight Analyzer Diagnostic Device (Allegro) gives
a wavefront map, sagittal and tangential power maps, and
analysis of Zernike coefficients. It automatically detects
keratometric values during surface ablation procedures
(Figure 10).
Limitations
It has similar limitations to the Hartmann Shack method. As
all the spots are observed simultaneously highly aberrated
eyes cause confusion as to the origin of the observed spots.

38 l DOS Times - Vol. 20, No. 7 January, 2015

Refractive Surgery

Figure 12: Principle of ray tracing aberrometry.

from a superior direction is located below the optical axis in Limitations
a myopic eye and above the optical axis in a hyperopic eye. The scan area is an annulus of 2mm x 6mm. Therefore this
Because the retina can be considered a spherically concave does not analyze the central area of the optical system.
mirror (reflecting about 4% of the incident light), the beam Also, because the system measures along meridians the
is reflected back in more or less the original direction in a detection of radially symmetric modes are problematic.
myopic eye. In a hyperopic eye, however, the reflection Thus the system either under or over estimates common
is directed to the opposite side of the pupil. Moving the modes such as trefoil, tetrafoil and pentafoil.
incident beam along a certain pupillary meridian (indicated Ray Tracing aberrometry
by arrows in the figure) will result in a reflected beam that Principle
goes in the same or the opposite direction as the incident Ray tracing employed most widely by iTrace (Tracey
beam. The difference in direction and the ratio between technologies) uses sequential ray tracing as a mechanism
the speed of the incident beam and that of its reflection can to analyze the aberrations of an optical system. In this
then be used to estimate the ocular refraction along this instrument a thin laser beam is projected through the
meridian15. entrance pupil at a very high speed following a concentric
The retina is scanned with an IR beam, and the time matrix (Figure 12).
difference of reflected light is captured by an array of Each beam produces a spot on the retina the location of
rotating photo detectors over the 360° of the retina. which is monitored by semiconductor photo detectors.
Therefore light passing through a scanning slit is compared Once the position of one spot is determined the laser
to the reference light from a diode array. beam moves to determine the location of another spot on
Machine using Differential Skiascopy the retina. This process is done till 256 points have been
The OPD-Scan III (Nidek, Inc., Fremont, CA) machine has projected through the entrance pupil.
a wide measurement area of 9.5mm, which measures 2520 In this way the error distance (x,y) of each point from
data points. It gives an overview summary, which provides the fovea is determined. This helps find the theoretical
refractive data, and incorporates corneal disease analysis conjugate focal points for each spot, which in turn tells
software and data for cataract and refractive surgery. It us the transverse aberration for that point at the entrance
gives information about corneal spherical aberration, pupil.
corneal indices, astigmatism and pupil information. It can
identify early cataracts, which show increased internal Machine using the Ray tracing Principle
aberrations. It also gives information about pupil size, iTrace measures aberrations over the whole eye over a
optical quality indices, higher order point spread function, flexible measurement zone of 2-8mm. It also provides,
cornea summary, toric IOL planning, wavefront summary multi-zone refraction analysis, for day to night vision
and the Holladay summary (Figure 11).

www. dosonline.org l 39

Diagnostics: Four Aces of Refractive Surgery: Aberrations Aberrometers Applications and Advances

Figure 14: Pentacam printout of a patient showing
the entire wavefrontrepresented in the form of 1st to

6th order Zernike polynomials.

Figure 13: iTrace (Tracey Technologies) machine. In 1934, Fritz Zernike published a paper describing a
set of polynomials that could be used to expand the
assessment, over refraction with spectacle or contact lens, aberration data. Each polynomial represents a particular
and in addition to a complete topographic analysis also mode of optical aberrations. Thus the entire wavefront
measures accommodative volume (Figure 13). can be described by coefficients, which when taken as a
Advantages whole reconstructs the wavefront map, but individually
It makes measurements in highly aberrated eyes with a describe the relevant amount of each aberration mode.
dynamic range of +/- 15D. The diameter of the 256-beam Different modes allow us to visualize the primary types of
matrix can be adjusted according to the pupilsize. One can aberrations, which contribute to the overall deviation.
select azone of interest however one must remember each The first to sixth orders Zernike polynomials are shown
spot is not immune to blurring by microaberrations. graphically in this figure. The zero order has one term. The
An interesting point to note is that the technology used first order has two terms that represent tilt for the x and y
by this machine was initially used by the Institute of axes. The second order includes three terms that represents
Biomedical Engineering of Kiev (Ukraine) for missile and defocus and regular astigmatism in the two directions. The
satellite tracking! third order has four terms that represent coma and trefoil,
How do we describe these deviations? What are and similarly, the fourth order has five terms that represent
Zernike Polynomails? tetrafoil, secondary astigmatism and spherical aberration.
A wave front is an imaginary surface joining all points (Figure 14).
in space that are reached at the same time by a light The polynomials can be expanded up to any random order
wave propagating through a medium. A deviation of the if a sufficient number of measurements are made for the
wavefront that originates from the optical system, from calculations. The unit for wavefront aberrations is microns
a reference wavefront that comes from an ideal optical or fractions of wavelengths and is expressed as the root
system constitutes a wavefront aberration6. mean square or RMS.Monochromatic aberrations can be
In order to make the understanding of this data easy, the evaluated quantitatively using the Zernike coefficients for
wavefront error is broken down into data and can be each term2.
analyzed by using certain numerical terms called Zernike References
polynomials2.
1. Atchinson, D.A. and Smith, G. (2006) Optics of the human eye,
Butterworth-Heinmemann.

2. Maeda N. Clinical applications of wavefront aberrometry - a review.
Clin Experiment Ophthalmol. 2009;37:118-29.

3. Roorda A. A review of basic wavefront optics. In: Krueger RR,
Applegate RA, MacRae SM, eds, Wavefront Customized Visual
Correction; the Quest for Super Vision II. Thorofare, NJ, Slack, 2004;
9–18.

4. Sergienko NM, Tutchenko NN. Depth of focus: clinical manifestation.
Eur J Ophthalmol 2007;17:836–40.

40 l DOS Times - Vol. 20, No. 7 January, 2015

Refractive Surgery

5. Rocha KM, Vabre L, Chateau N, Krueger RR. Expanding depth of 11. Molebny VV, Panagopoulou SI, Molebny SV, Wakil Y, Pallikaris IG.
focus by modifying higher-order aberrations induced by an adaptive Principles of ray tracing aberrometry. J Refract Surg. 2000;16:S572–
optics visual simulator. J Cataract Refract Surg 2009;35:1885-92. 75.

6. Mello GR, Rocha KM, Santhiago MR, Smadja D, Krueger RR. 12. Burns SA. The spatially resolved refractometer. J Refract Surg2000;
Applications of wavefront technology. J Cataract Refract Surg. 16: S566–9.
2012;38:1671-83.
13. MacRae S, Fujieda M. Slit skiascopic-guided ablation using the
7. Kawamorita T, Uozato H. Modulation transfer function and pupil Nidek laser. J Refract Surg. 2000; 16: S576–80.
size in multifocal and monofocal intraocular lenses in vitro. J
Cataract Refract Surg 2005;31:2379-85. 14. Rozema JJ, Van Dyck DE, Tassignon MJ. Clinical comparison of 6
aberrometers.Part 1: Technical specifications. J Cataract Refract
8. Tyson RK. History and background. In: Principles of Adaptive Surg. 2005;31:1114-27.
Optics, 2nd edn. Boston, MA: Academic press, 1998; 1–25.
15. MacRae S, Fujieda M. Slit skiascopic-guided ablation using the
9. Thibos LN. Principles of Hartmann-Shack aberrometry. J Refract Nidek laser. J Refract Surg 2000; 16:S576– S580.
Surg2000; 16: S563-65.

10. Mrochen M, Kaemmerer M, Mierdel P, Krinke HE, Seiler T. Principles
of Tscherning aberrometry. J Refract Surg. 2000;16: S570–1.

www. dosonline.org l 41

MReifsrcacetlilvae nSueroguersy

Vitreomacular Traction:
Management
Raji K.

MS, DNB

Raji K. MS, DNB, A.K. Upadhyay MS, S. Waikar MS, DNB, P. Tiwari MBBS
Department of Ophthalmology, Command Hospital (WC) Chandimandir

Vitreous is a clear gel that occupies the posterior segment are useful tools to diagnose PVD in such circumstances
of the eye which is made up of 98% water and 2% (Figure 1).
macromolecules1,2. The outer cortex of vitreous which is Posterior Vitreous Detachment (PVD) and
made up of dense collagen (Type II) is firmly attached to anomalous PVD
internal limiting membrane (Type IV collagen). Vitreous is Outer cortex of vitreous is made up of type II collagen which
strongly attached at vitreous base, optic disc and to some is strongly attached to internal Limiting membrane (type IV
extend on macula. As the age advances, gel undergoes Collagen). With the advancing age vitreous gel liquefies,
liquefaction and attachment between vitreous and internal a process called synchysis and collapses which is known
limiting membrane (ILM) weakens and it gets completely as syneresis. As the age advances vitreous detaches from
separated which is called posterior vitreous detachment retina, a process known as Posterior vitreous Detachment
(PVD), which usually begins in the perifoveal macula3,4. (PVD) (Figure 2). Though some people experience some
PVD occurs in two phases liquefaction followed by floaters, generally PVD is asymptomatic. If vitreo retinal
separation. The completion of vitreo-papillary separation adhesions are not weakened at places, patients can be
often characterized by the Weiss ring is usually an acute symptomatic which is known as anomalous PVD. The
and symptomatic event. Inadequate or incomplete vitreo- effects of persistent traction on optic disc (vitreo papillary
retinal interface separation result in anomalous PVD with adhesion) can lead to neovascularization of optic disc(NVD)
vitreo-macular interface (VMI) anomalies. Anomalous PVD especially in diabetics, which can lead to haemorrhage and
is defined as partial vitreous detachment with persistent loss of vision. Traction near vitreous base cause tears and
attachment in the macular region featuring an anomalous retinal detachment. When perifoveal vitreous cortex gets
strength of adhesion to one or more structures in the attached on to macula after detached from surroundings,
posterior pole, resulting in tractional deformation of retinal Focal VMA develops7, which is usually asymptomatic. Or
tissue5.
Definition and Classification of Vitreomacular Figure 1: Fundus photograph and OCT scan of normal normal macula. *
Adhesion formerly known as inner segment – outer segment junction. interdigitation
Vitreomacular adhesion (VMA) denotes residual strong
adhesion between vitreous and macula when PVD is between photo receptors outer segment and RPE.
incomplete.
With the evolution of Optical Coherence Tomography
visualization and understanding of the vitreo-retinal
interface has improved6. OCT is central to diagnosis and
increased the likelihood of detecting VMT. When vitreous
separation is full and complete, detached vitreous is difficult
to detect by OCT. Clinical examination and ultrasound

www. dosonline.org l 43

Miscellaneous: Vitreomacular Traction: Management

Figure 2: Stages of PVD. Johnson and Sebag4,5. Stage 1: applicable classification system to identify, monitor and
Perifoveal detachment. Vitreous attached to fovea, optic disc manage vitreomacular interface disorders. This is based
and mid –peripheral retina. Stage 2: Vitreous attached to optic on multiple OCT B-line scans images and classified by
disc and mid periphery. Stage 3 PVD: Vitreous detached from the size of attachment or lesion and presence of retinal or
fovea, mid- peripheral retina and attached only at optic disc. vitreoretinal conditions8.

Stage 4: Complete PVD. Definitions of Macular hole and Pseudo Hole
Impending macular hole: It is described in cases where
VMA is described as residual adhesion between vitreous there is full thickness macular hole in one eye and VMT is
and macula, when there is incomplete PVD. If traction observed in the fellow eye.
is enough to cause disturbance in macular architecture Full thickness macular Hole: Full thickness lesion with
VMA can lead to VMT, which is always pathologic and interruption of all layers of retina from ILM to RPE. If size
symptomatic. Vitreomacular Traction (VMT) is defined of the hole is <400µm, pharmacological vitreolysis can
as structural abnormality associated with loss of vision. be tried. Chances of FTMH closure (40.6%) at day 28 vs
Symptoms associated with VMT are blurring of vision, placebo (10.6%). Lamellar macular hole: round or oval
metamorphopsia and difficulty in reading. reddish lesion with partial thickness foveal defect. OCT
Vitreomacular Adhesion: focal adhesion of the vitreous features include irregular foveal contour, intra retinal
face within macular region. splitting,
Vitreomacular Traction: VMA causing focal tractional Broad VMA and tractional Macular Thickening: when VMA
distortion of macula. is > 1500µm, it can cause schisis of retinal layers.
Vitreo macular traction syndrome: VMT associated with ERM and macular pucker: cause of ERM is not completely
loss of visual function known. After PVD vitreous remnants are attached to
Symptomatic VMA: VMT syndrome, macular hole or cases the surface of retina (vitreoschisis), which stimulate
where normal or abnormal VMA coexist with macular proliferation of hyalocytes, glial cells and histiocytes on its
diseases, with loss of vision. surface cause development of ERM. Centripetal tractional
International Vitreomacular Traction Study (IVTS) Group forces on retinal surface cause macular pucker.
has developed a simple, evidence based clinically Pseudohole: ERM with central opening can give rise to
Pseudo hole formation which appear as round or oval
shaped defect. Surgical membrane peeling is advised in all
these condition.

Treatment of Vitreomacular Adhesion
Observation: Focal VMA can resolve spontaneously even
without treatment. Amsler grid evaluation is advocated in
patients with asymptomatic focal VMA.
Pharmacological vitreolysis should be considered when
VMA has progressed to VMT. These agents break down
the peptide bonds in laminin and fibronectin molecules
which keeps the adhesion between ILM and vitreous.
Collagenase, chondroitinase, hyaluronidase,plasmin,
plasminogen activator are few agents used for vitreolysis.
Plasmin is manufactured from patients own blood and it
is very unstable. Ocriplasmin, is a recombinant truncated
form of human plasmin with molecular weight 27.8kDa.
it is a DNA molecule which is more stable than plasmin
and has emerged as new vitreolytic agent. It is recombinant
protease with activity against fibronectin and laminin.
VMT and FTMH with focal VMA are called symptomatic
VMT: in macular holes with VMT, Pharmacological
vitreolysis are indicated. Ocriplasmin was approved for
treatment of symptomatic VMA and VMT, including
macular hole with diameter <400µ. In patients with

44 l DOS Times - Vol. 20, No. 7 January, 2015

Refractive Surgery

Figure 3: Optical coherence tomography (OCT) scans illustrating (A-C) vitreomacular adhesion (VMA) and (D-F)
vitreomacular traction (VMT) according to International Vitreomacular Traction Study Classification System.

Anatomical State IVTS classification system
VMA
Definition
VMT Evidence of perifoveal vitreous detachment from retinal surface vitreous cortex attached to
macula within a radius of 3mm no change in foveal anatomy
FTMH Classification: by extend of attachment area- focal <1500µm, Broad >1500µm: Isolated
absence of concurrent retinal condition,
LMH Concurrent: associated with retinal anomaly
Macular pseudohole Definition: Evidence of perifoveal vitreous detachment from retinal surface vitreous cortex
attached to macula within a radius of 3mm
Associated with distortion of foveal surface, intraretinal structures,
Classification: by extend of attachment area- focal <1500µm, Broad >1500µm:
Isolated absence of concurrent retinal condition,
Concurrent: associated with retinal anomaly
Full thickness macular lesion, interrupting all layers from ILM to RPE
Classification: By Size
Small≤250µm
Medium≥250 µm and ≤400µm
Large ≥400µm
By presence or absence of VMT
By cause: Primary (initiated by VMT)
Secondary (trauma or associated disease)
Definition: irregular foveal contour
Defect in the inner fovea
Intraretinal splitting
Intact photoreceptor layer
Definition: invaginated or heaped foveal edges
Concomitant ERM with central opening
No loss of retinal tissue
Steep macular contour to central fovea with near normal central foveal thickness.

isolated VMT, without ERM had resolution by 28 days after occlusion is poorly understood. If there is no release of
single injection of 0.125mg/0.1ml ocriplasmin (29.8%) as VMT, patients can undergo PPV. 30-50% of stage I MH
compared to placebo injection (7.7%)9. Natural history regress spontaneously where as only 10% stage II and
of VMT associated with AMD, DME and retinal vein III holes do so. 125 µg Ocriplasmin injection resulted in

www. dosonline.org l 45

Miscellaneous: Vitreomacular Traction: Management

Figure 4: Full-Thickness Macular Hole (FTMH)

spontaneous resolution of FTMH in 40.6% (MIVI TRUST- laminin which is present in other layers of retina, including
Microplasmin for IntraVitreous Injection- Traction Release Bruch membrane, interphotoreceptor matrix, External
without Surgical Treatment) of patients, within 28 days limiting membrane, Outer plexiform layer, inner plexiform
versus placebo (10.6%). Closure rates were higher in small layer and ILM. Though the effect on photoreceptor outer
FTMH (58.3%) as compared to medium (36.8%) and large segment is transient, the action on rods is more prolonged.
MH (0%). Only 8.7% of eyes with FTMH with ERM had Surgical treatment: Pars Plana Vitrectomy (PPV) with ILM
resolution of VMT. peeling is the standard treatment advocated for VMT. The
Side Effects of ocriplasmin success of relieving VMT ranges from 80-90%. The surgery
Ocular adverse effects of Ocriplasmin injection are helps to improve blurred and distorted vision, also can help
vitreous floaters, photopsia, blurred vision, conjunctival in improving vision. But this can be associated with various
harmorrhage, potential for lens subluxation, retinal breaks complications like retinal breaks, retinal detachment,
and dyschromatopsia (as yellow vision). ERG changes in endophthalmitis, and development of cataract.
the form of reduced ‘a’ and ‘b’ wave amplitude is reported Summary
in patients experiencing dyschromatopsia. Patients can Clinical outcome depends on ability of treating physician’s
experience transient loss of vision, which is attributed to ability to form correct diagnosis and treat accordingly.
the disruption in the ellipsoid layer( previously known Untreated cases can lead to permanent damage to retina.
as photoreceptor IS/OS junction). Wide spread retinal With the availability of non-surgical treatment patients
dysfunction can develop in patients due to its effect on comfort and quality of life can be improved.

46 l DOS Times - Vol. 20, No. 7 January, 2015

Refractive Surgery

References 6. Koizumi H, Spaide RF, Fisher YL,et al. Three dimensional evaluation
of vitreo-macular traction and epiretinal membrane using spectral
1. Sebag J. Vitreous: the resplendent enigma. Br J Ophthalmolo domain optical coherence tomography.Am J Ophthalmol 2008;
2009;93: 989-91. 145: 509-17.

2. Bishop PN. Structural macromolecules and supramolecular 7. Kroll P, Wiegand W, Schmidt J. Vitreopapillary traction in proliferative
organization of vitreous gel. Prog Retin Eye Res2000;19: 323-44. diabetic vitreoretinopathy.. Br J Ophthalmol 1999;83:261-64.

3. Johnson MW. Perifoveal vitreous detachment and its macular 8. Sebag J, Wang MY, Nguyen D, sadun AA. Vitreopapillary adhesion
complications. Trans Am Ophthalmolo Soc 2005; 103:537-67. in macular diseases. Trans Am Ophthalmol Soc 2009;107:35-44.

4. Uchino E, Uemura A,Ohba N. Initial stages of posterior vitreous 8. Duker JS, Kaiser PK, Binder S, et al. The international Vitreomacular
detachment in healthy eyes of older persons evaluated by optical Traction Study Group Classification of Vitreomacular adhesion,
coherence tomography. Arch Ophthalmolo 2001;119: 1475-9. traction, and macular Hole. Ophthalmol 2013;120:2611-19.

5. Sebag J. Anomalous posterior vitreous detachment: a unifying 9. Stalmans P, Benz MS, Gandorfer A, et al. Enzymatic vitreolysis with
concept in vitreo-retinal disease. Graefes Arch Clin Exp Ophthalmolo ocriplasmin for vitreomacular traction and macular holes. N Eng J
2004; 242: 690-8. Med 2012: 367;606-15.

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Madhya Pradesh. Over the last 50 years, Sadguru Netra
Chikitsalaya has contributed extensively to the field of
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ophthalmic techniques and its community-based outreach
activities. In 2014-2015, over 125, 000 surgical procedures

were performed in the hospital through its direct and outreach services. The institution is calling eligible medical professionals for:

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www. dosonline.org l 47

RefraEctvivoelSuutrigoerny

Presbyopia- Evolution
and Current Management

Vijay Kumar Sharma
MS

Vijay Kumar Sharma MS, Tarun Arora MD, DNB, FICO, Rajesh Sinha MD
Dr. Rajendra Prasad Centre for Ophthalmic Sciences,
All India Institute of Medical Sciences, New Delhi

The correction of presbyopia and the restoration of theory of sclerosis of the crystalline lens as the cause of
accommodation are considered the final frontier of Presbyopia has been challenged in 1992 by Schachar2.
refractive surgery. Presbyopia is a physiologic inevitability Schachar suggests that the longitudinal muscle fibers of
that causes the gradual loss of accommodation. The the ciliary muscle contract during accommodation, placing
accommodative ability of the eye starts to decline usually more tension on the equatorial zonules, while relaxing
after the age of 40-45 years. In 2005, the estimated global the anterior and posterior zonules. This force distribution
impact of presbyopia was 1.04 billion people, with over causes an increase in the equatorial diameter of the lens,
the half not having adequate near-vision correction, and decreasing the peripheral volume while increasing the
410 million people listed as visually impaired (94% in central volume. As the central volume increases, so does
developing countries)1. the power of the lens. Under this theory, Presbyopia occurs
Historical perspectives because of the increasing equatorial diameter of the aging
Chinese are credited with inventing eyeglasses to correct or
aid vision in 13th century. Marco Polo in 1270, noted them Figure 1: Benjamin Franklin- Inventor of
wearing glasses on the head. However around the same bifocal reading glasses
time, in Florence, Italy, the Dominican friar Alessandro
Della Spina and his friend, the physicist Salvino Degli
Armati, also developed glasses. The tombstone of Armati,
who died in 1317, bears the inscription “the inventor of
spectacles”. Perhaps the earliest treatment of Presbyopia
was invented as early as 1784 when Benjamin Franklin
designed Bifocal spectacles (Figure 1). Patients with
presbyopia have several options for eyeglass correction:
bifocals, trifocals, progressive addition lenses, or separate
eyeglasses for distance and reading.
The pathophysiology of Presbyopia still remains poorly
understood. Various theories have been put forward to
explain loss of accommodation with age. According to a
theory proposed by Helmholtz, accommodation occurs as
a result of the elastic properties of the lens and possibly
the vitreous that allows the lens to expand and increase
its power when zonular tension is relieved during ciliary
muscle contraction. As the lens changes with age, the ability
to expand and increase refractive power is lost. Helmholtz’s

www. dosonline.org l 49

Evolution: Presbyopia- Evolution and Current Management

Table 1: Current surgical treatment options for presbyopia

Cornea Lens Sclera
Anterior ciliary sclerotomy
Monovision (LASIK and PRK) Monovision (Monofocal IOL)

Presbyopic LASIK (multifocal Laser Multifocal IOL
ablation)

Conductive keratoplasty Accomodative IOL

Intracor Femtosecond laser

Corneal inlay

lens. Once the lens diameter reaches a critical size, usually three different approaches that have been used for corneal
during the fifth decade of life, the resting tension on the multifocality: transitional multifocality, central presbyLasik
zonules is significantly reduced. (center for near) and peripheral presbyLasik (peripheral
Current surgical procedures to treat presbyopia cornea for near) and concluded that although central
In the last decades there have been several attempts to presbyLasik creates a bifocal cornea, the other techniques
correct presbyopia in order to eliminate the dependence on increase the depth of focus based on the ablation of the
reading glasses. The number of different techniques and the peripheral cornea. Transitional multifocality creates
variety of approaches arises from the partial effectiveness intentionally an increase in coma aberration. Based
of most methods to restore true accommodation. The on the published results, both central and peripheral
anatomical site of the procedure differs, depending on the presbyLasik resulted in adequate spectacle independence
method utilized (Table 1). simultaneously for far and for near. A neuroadaptation
Corneal procedures process is necessary for peripheral presbyopic LASIK. Very
Monovision LASIK and surface ablations (PRK, LASEK, Epi- recently, a new proprietary ablation pattern (Supracor,
LASIK) Bausch and Lomb/Technolas, Munich, Germany) was
Monovision has been used to compensate for presbyopia by applied using a profile that steepens the center of the
optically correcting one eye for distance vision and the other cornea to create hyperprolate shape resulting about 2 D
eye for near vision. This strategy induces anisometropia near addition with controlled higher order aberrations
with a consequent reduction in binocular acuity and (HOA). Ninety-six percent of the patients were satisfied
stereopsis. Success rates for monovision refractive laser with this procedure at 6 months.
correction have been reported to be high (72 to 92%)3. Different presbyopic laser ablation profiles currently offer
Factors related to better outcomes are associated with an alternative treatment for presbyopia. Many of these
anisometropia of less than 2.50 diopters (D), good distance techniques are still under evaluation today. Long-term
correction of the dominant eye, stereo acuity reduction of scientific evidence is necessary to assess their role toward
less than 50’ of arc, distance esophoric shift of less than 0.6 spectacle or contact lens independence for near.
prism diopters and highly motivated patient who can adapt Presbyopic femtosecond laser ablation (Intracor)
to monovision. The utilization of femtosecond laser technology in
The amount of target refraction in monovision remains ophthalmology, introduced new techniques in the field
controversial. Some authors suggest correcting up to –2.50 of refractive surgery4. Femtosecond laser pulses applied
D, whereas others suggest not exceeding –2.00 D. Patient in a concentric ring fashion inside the corneal stroma
age, occupation, needs and lifestyle plays a role in the were able to induce changes in the corneal shape without
decision of the amount of target correction in monovision. cutting a flap. Ruiz et al. performed and published for
Patient selection is very important for the outcomes and the first time the Intracor procedure using a Technolas
high patient satisfaction of any monovision procedure. Femtosecond Laser (Bausch and Lomb Technolas, Munich,
Presbyopic excimer laser ablation Germany). In this proprietary procedure, the pattern of
Attempts to create multifocal profiles to correct presbyopia laser delivery is entirely intrastromal, without impacting the
have been made since 1992 using Excimer laser. The endothelium, Descemet’s membrane, Bowman’s layer, or
introduction of LASIK in refractive surgery offered a more epithelium at any point throughout the operation, creating
effective and controllable technique for the creation of a central steepening of the anterior corneal surface.
multifocal, bifocal or other profiles. Alio et al. reviewed Such a procedure has several potential advantages: No
epithelial disruption, no pain and inflammation related
to the absence of epithelium and quick recovery. Early
results of this procedure yielded a significant and stable

50 l DOS Times - Vol. 20, No. 7 January, 2015

Refractive Surgery

Figure 2: Kamra inlay

gain of uncorrected near visual acuity (UNVA) and corneal regression of refractive and keratometric effects of CK has
steepening, without a significant loss of endothelial cells been observed over short-, mid- and long-term follow up
or corneal thinning up to 18 months postoperatively5. No period, limiting the usage of this procedure.
significant regression of visual acuity or further corneal
steepening occurred during the follow-up period. Intracor Corneal inlays
has also some disadvantages: It can lead to a reduction Intracorneal implantation of a lens is not a novel idea.
of mesopic contrast sensitivity and an increase of glare Jose Barraquer developed and experimented with the
sensitivity according to the study conducted by Fitting et al. first prototype in 1949. He soon abandoned this idea
The authors suggested that possible consequences on night because of the corneal tissue’s aggressive response to the
driving ability should be discussed with the patients prior flint glass material. The discovery of hydrogel and other
to treatment. Further studies with larger number of eyes are more biocompatible materials revived the concept of
required to assess the safety, efficacy and long-term stability corneal inlays, two decades later. The new materials were
of this new procedure. transparent and permeable to nutrients and promised to be
Conductive keratoplasty well-tolerated by the corneal tissue. They had, however,
Conductive keratoplasty (CK) is a non-invasive, in-office many complications: Thinning and melting of the overlying
procedure for the correction of hyperopia, hyperopic stroma, corneal opacification, decentration and haze that
astigmatism, and management of presbyopia. It is based led to explantation of many of these devices.
on radiofrequency energy delivered through a fine needle Keates et al (1995) reported their results of using the small-
tip that is inserted into the peripheral corneal stroma in a diameter corneal inlay to create a bifocal cornea to correct
ring pattern. A series of spots (8-32) are placed in up to presbyopia. According to the authors, uncorrected near
three rings of 6-, 7-, 8-mm optical zones in the corneal vision had improved from J4 to better than J2 in four of
periphery. The shrinkage of collagen between the spots the five eyes implanted at 12 months postoperatively. The
creates a band of tightening, which results in steepening newest generation of corneal inlays is made of materials
of the central cornea. The United States Food and Drug with enhanced biocompatibility6. Advances in technology,
Administration approved this procedure about a decade ago such as femtosecond lasers, facilitate the easier, more
for the temporary correction of mild to moderate spherical reliable creation of stromal pockets, offer better estimation
hyperopia in people over 40 years old. It is applied as of implantation depth and improve centration of corneal
a monovision procedure in the non-dominant eye of inlays. Currently, there are three different designs of
presbyopic individuals. The advantages of CK include that it presbyopic corneal inlays.
is a minimally invasive, in-office and relatively cost-effective Small aperture inlay (Kamra, Acufocus Inc, Irvine, CA,
procedure. However, it has significant contraindications in USA) that increases the depth of field using the pin-hole
eyes with corneal disease and dry eye syndrome. Various effect to restore near and intermediate visual acuity without
studies evaluated the safety and efficacy of CK. Although significantly affecting distance vision7 (Figure 2). The
satisfactory NUCVA was reported initially, significant AcuFocus Kamra corneal inlay is a 5μ-microperforated

www. dosonline.org l 51

Evolution: Presbyopia- Evolution and Current Management

artificial aperture (3.8 mm outer diameter; 1.6 mm inner Figure 3: Raindrop or hydrogel corneal inlay
diameter) made of polyvinylidene fluoride, a material
reported to be highly biocompatible in vitro. It is implanted Figure 4: Flexivue Corneal Inlay
unilaterally in the non-dominant eye. The inlay received the
Conformité Européenne (CE) mark for use in the European simultaneous images, either monocularly using multifocal
Union in 2005. The initial reports show an improvement in IOLs or binocularly through monovision. In monovision,
all tested reading performance parameters in emmetropic one eye is optimized for distance vision and the other eye
presbyopic patients, as the result of an increased depth for near, as described in the corneal procedures. Another
of field. The Kamra inlay implantation can be combined option is to utilize accommodative IOLs that use the ciliary
with LASIK improving near vision with a minimal effect on muscle contraction to change the refractive state of the eye
distance vision, resulting in high patient satisfaction and by shifting the IOL position.
less dependence on reading glasses according to a recent Multifocal IOL
paper by Tomita et al. The multifocality of the latest generation IOLs is based
Space-occupying inlays that create a hyperprolate cornea on refractive and diffractive technology. Excellent clinical
(Raindrop, Revision Optics, Lake Forest, CA, USA). The outcomes have been reported with different IOLs.
Raindrop Near Vision inlay is made of hydrogel, is 32 μ Patient selection is very crucial in order to avoid patient
thick and has a diameter of 2 mm8 (Figure 3). In the first dissatisfaction and secondary procedures for IOL exchange.
published paper in a peer-reviewed journal, Garza et Until recently, most multifocal IOLs could provide
al. concluded that the hydrogel corneal inlay improved satisfactory vision for far and either near or intermediate
uncorrected near and intermediate visual acuity in 20 distance. They were actually bifocal lenses. The most
patients with emmetropic presbyopia, with high patient recent multifocal IOLs with improved optics have enhanced
satisfaction and little effect on distance visual acuity at 1 intermediate distance, giving the patient a full range of
year postoperatively. vision. Multifocal IOLs reduce contrast sensitivity and cause
Refractive annular addition lenticules that work as bifocal more glare and halos in comparison to monofocal IOLs.
optical inlays separating distance and near focal points
(Flexivue Microlens, Presbia, Irvine, CA, USA). The Presbia
Flexivue Microlens is made of a hydrophilic polymer, has
a diameter of 3 mm and its edge thickness is approximately
15 μm (Figure 4). The central 1.6 mm zone of the inlay
is optically neutral. The Flexivue Microlens has a 0.5 mm
hole in the center for allowing adequate nutritional flow
in the cornea. Limnopoulou et al. reported uncorrected
near visual acuity of 20/32 or better in 75% of operated
eyes, whereas mean uncorrected distance visual acuity
(UDVA) decreased statistically significantly from 0.06
logMAR (20/20) preoperatively to 0.38 logMAR (20/50)
postoperatively. Mean binocular UDVA was not significantly
altered. Overall, higher order aberrations increased and
contrast sensitivity decreased in the operated eye. No tissue
alterations were found using corneal confocal microscopy.
A great advantage of the corneal inlays is their potential
reversibility. Although the initial papers show encouraging
results, further studies and longer follow up are needed for
the clinical assessment of the inlays.
Lens procedures
In the last decades cataract surgery has evolved to a
refractive procedure, in which the ophthalmic surgeon
attempts to correct all or most of the refractive errors of
the patient, including presbyopia, in a single operation.
Currently, there are different approaches in IOL optic
design to compensate for the loss of accommodation.
One approach is to provide the visual system with two

52 l DOS Times - Vol. 20, No. 7 January, 2015

Refractive Surgery

In some cases, these optical phenomena can be disturbing develop during ciliary muscle contraction. The procedure
and a secondary intervention and IOL explantation might is hypothesized to restore accommodative amplitude in
be required. The most common reason for explantation or presbyopic subjects. Although various studies have shown
secondary intervention was glare/optical aberrations (68%), that anterior ciliary sclerotomy or any other scleral surgical
followed by incorrect IOL power (21%). Precise biometry technique is not very effective treatment for the correction
for IOL calculation and correction of astigmatism is crucial of presbyopia. Better controlled studies are needed for the
for a good outcome after multifocal IOL implantation. evaluation and the possibility of utilization of this technique
Accommodative IOL in the future, based on scientific evidence.
Current accommodative IOL designs have either single Conclusion
or double lens systems that are based on the “focus shift” At present, the ophthalmic surgeon has several options
principle. Theoretically, the contraction of the ciliary for the correction of presbyopia in individuals who
muscle moves the optic anteriorly, thereby increasing the wish to decrease their dependence on reading glasses.
dioptric power of the eye. Menapace et al. found that axial Improvements in technology have advanced surgical
shift and thus true accommodative effect was small or options, offering a variety of approaches. The restoration
even absent, and also very variable, making an individual of accommodation, which is considered the final frontier in
prediction impracticable. In a study by Klaproth et al., refractive surgery, still remains a challenge.
comparing different accommodative IOLs based on the References
principle of using ciliary muscle contraction for moving the
IOL or changing its thickness and/or surface radii during 1. Holden BA, Fricke TR, Ho SM, Wong R, Schlenther G, Cronjé S, et
accommodation in order to change the ocular refractive al. Global vision impairment due to uncorrected presbyopia. Arch
power, the authors concluded that a proof of principle of Ophthalmol. 2008;126:1731–9.
such lenses under physiological, non-pharmacologically
stimulated conditions is still lacking. In a recent paper by 2. Schachar RA. Cause and treatment of presbyopia with a method
Zamora-Alejo et al., no significant signs of accommodation for increasing the amplitude of accommodation. Ann Ophthalmol.
were found with a single-optic accommodative IOL. The 1992;24:445–7. 452.
accommodative IOL showed some benefit for intermediate
visual function compared to monofocal IOLs with both 3. Farid M, Steinert RF. Patient selection for monovision laser refractive
groups wearing full correction for distance. Alio et al. surgery. Curr Opin Ophthalmol. 2009;20:251–4.
compared the visual and ocular optical performance in
eyes with a single-optic or a dual-optic accommodating 4. Ruiz LA, Cepeda LM, Fuentes VC. Intrastromal correction of
intraocular lens. They found that eyes with the dual-optic presbyopia using a femtosecond laser system. J Refract Surg.
IOL had significantly better ocular optical quality. Further 2009;25(10):847–854.
studies are necessary to provide evidence of the efficacy of
single- or double-optic accommodative lenses. 5. Holzer MP, Mannsfeld A, Ehmer A, Auffarth GU. Early outcomes
Scleral procedures of INTRACOR femtosecond laser treatment for presbyopia. J Refract
Anterior ciliary sclerotomy is based on Schachar’s theory Surg. 2009;25:855–61.
and involves making radial incisions in the sclera overlying
the ciliary muscle9. According to this theory, radial 6. Waring GO, 4th, Klyce SD. Corneal inlays for the treatment of
sclerotomies allow expansion of the sclera overlying the presbyopia. Int Ophthalmol Clin. 2011;51:51–62.
ciliary body, increasing the space between the lens equator
and the ciliary body. This may place more resting tension 7. Tomita M, Kanamori T, Waring GO, 4th, Nakamura T, Yukawa S.
on the equatorial zonules, allowing for increased tension to Small-aperture corneal inlay implantation to treat presbyopia after
laser in situ keratomileusis. J Cataract Refract Surg. 2013;39:898–
905.

8. Garza EB, Gomez S, Chayet A, Dishler J. One-year safety and
efficacy results of a hydrogel inlay to improve near vision in patients
with emmetropic presbyopia. J Refract Surg. 2013;29:166–72.

9. Hamilton DR, Davidorf JM, Maloney RK. Anterior ciliary sclerotomy
for treatment of presbyopia: A prospective controlled study.
Ophthalmology. 2002;109:1970–6.

www. dosonline.org l 53

Principles of Kerato- RePfraGctivCe Sourrngeerry
Refractive Surgery
Abhishek Dave
MD, FMRF, FICO

Abhishek Dave MD, FMRF, FICO Vinay Arora MS, Sridevi Gunda DNB
Prachi Jhala Dave MS, DNB, Umang Mathur MS, FLVPEI

Cornea & Refractive Surgery Services, Dr. Shroff’s Charity Eye Hospital, New Delhi.

Refractive surgery procedures for the correction of myopia, steep corneas. Flatter corneas present less tissue through a
hyperopia, presbyopia and astigmatism can broadly be given ring size and produce smaller diameter flap increasing
divided into 2 categories: keratorefractive techniques and the risk of free-flaps.
lenticular and scleral based procedures. Keratorefractive Flap Thickness and Hinge Location
surgeries rely on at least five major methods to reshape Factors affecting flap thickness are head-plate depth, corneal
the corneal surface – incisions, lasers, thermal procedures, thickness, pre-operative refractive error, blade sharpness,
corneal implants and non-laser lamellar surgery. Incisional blade length, translational speed and intraocular pressure.
procedures and non-laser lamellar surgeries have largely The 2 most important patient factors that decide the head
been replaced by laser refractive procedures. Corneal plate depth are the corneal thickness and pre-operative
implants are mainly used in corneal ectatic disorders and refractive error2. IOP can affect flap thickness with lower
thermal procedures limited to hyperopic corrections. So IOP resulting in thinner flaps. Another important factor is
we will be limiting our discussion mainly to laser refractive the actual flap depth produced by different microkeratomes.
surgeries. The Flap Thickness Study Group found significant difference
Microkeratomes: Principles and Settings in the flap thickness produced by different microkeratome
The basic components of a microkeratome are: suction systems3. Now with the help of femtosecond lasers we can
ring, keratome head, blade control and variables. The main create thinner flaps thus giving us more room for ablation
variables are as follows: preserving a good residual bed. The femtosecond flaps
1. Suction ring size and flap diameter varies much less in thickness also.
2. Flap thickness and hinge location The two hinge locations used are superior and nasal.
3. Vacuum setting Superior hinge has the advantage of upper lid compression
4. Blade selection and controls maintaining flap position and centration. But the same
Suction Ring Size is associated with greater dry-eye symptoms due to the
The size of the suction ring is the primary determinant of the corneal hypoesthesia produced by severing of the nasal and
flap diameter. Preoperative keratometry influences the flap temporal nerve plexus. Nasally placed hinge fairs better in
diameter1. Use of a large diameter suction ring for patients this regard4. However few studies contradict this.
with steep corneas can result in flaps that exceed the clear Residual Posterior Stromal Thickness (RPST)
corneal diameter, resulting in damage to limbal vessels and This is the most important factor to be considered when
also increasing the chances of button-hole complications. choosing the flap thickness. A minimal RPST of 250
So a smaller diameter ring is recommended for significantly µm is essential to prevent post lasik ectasia5. But it is
recommended to preserve a RPST of 280-300 µm. Thus 250

www. dosonline.org l 55

PG Corner: Principles of Kerato-Refractive Surgery

µm plus the flap thickness are subtracted from the lowest Beam Homogeneity
central pachymetry to determine how much ablation can be This is a measure of the consistency of energy distribution
performed. The ablation depth can be approximated using applied over the ablation area. Poor beam homogeneity can
the Munnerlyn formula: Depth of Ablation = Dioptres of lead to irregular ablations. This becomes very important for
Correction X (Ablation Diameter)2/3. The decision to create customized ablations. Beam homogeneity can be verified
a thinner flap to treat higher powers should be weighed by test ablations performed on appropriate substrate
against the disadvantages of a thin flap i.e. higher risk of material provided by the manufacturer.
flap folds, buttonhole formation and increased difficulty in
handling thinner tissue. Beam size, Beam Delivery Systems & Ablation Profiles
Vacuum Setting The smaller the beam size, the easier it is to control the
The suction system should be sufficient to raise the IOP to homogeneity of the beam. The trade-offs for a smaller beam
at least 65 mm Hg. Lower pressure can produce thinner size include increased treatment time, corneal dehydrations
flaps and higher pressure increase risk of chemosis and and small amounts of decentration. Beam sizes of ≤ 1mm
optic nerve head injury. Newer microkeratome systems are adequate to correct up to Fourth-order Zernike terms.
automatically stop oscillations and forward progress if there There are three main types of beam delivery systems:
is loss of suction. 1. Full-beam Systems: They were used in first generation
Femtosecond Laser
Femtosecond laser consists of a solid state Nd: glass laser lasers. They offer more rapid treatment and are less
source generating pulses at rates of 3-5 kHz with each sensitive to decentration. However, they are more
pulse of 500 femtosecond duration and 3-5 µm size. Laser difficult to homogenize, yield less regular ablation
delivery occurs via a scanning spot ablating 0.3 µm/pulse surfaces and customized treatment is impossible.
with an accuracy of approximately 1 µm6. The vacuum 2. Scanning Slit Delivery: A diaphragm is placed between
system raises the IOP to around 35 mm Hg. The depth the eye and a full beam, creating a rectangular beam
accuracy achieved is around 10 µm. The first pulses are with a smaller width, improving homogeneity.
delivered along the hinge. A pocket is created to receive 3. Flying Spot: In this case beam is small and circular.
the gases. The edges of flap are prepared at last with a Beam direction is controlled by pivoting mirrors. Large
variable angle chosen by operator (60-90 degree) ensuring number of pulses, at a very high frequency is used,
maximal stability. FS laser has the potential advantages of each pulse removing only a very small area of tissue.
reduced flap complication rate, increased consistency of They have the advantage of providing asymmetrical
flap thickness and diameter, reduction in suction pressure ablation profiles.
required and flexibility of hinge creation. The principles for ablation in myopia, hyperopia and
Excimer Laser: Principles & Settings astigmatism have been depicted in (Figure 1, Figure 2) and
Principles (Figure 3) respectively.
The excimer laser utilizes a 193-nm UV wavelength
produced by the dissociation of an excited dimer, consisting Laser Room Environment
of Argon and Fluoride. The direct breakage of chemical The laser room environment is an important variable which
bonds by a high energy laser is called photochemical should be controlled. The room should be cool for optimal
ablation. Pulses produced are of approximately 10-nsec laser performance. The temperature varies from laser to
duration with laser repetition rates between 50 and 400 laser, but a temperature of 18-24°C is optimal. Ambient
Hz. Molecular fragments of approximately 10-20 carbon level humidity between 40-50 % should be maintained.
atoms are ejected in a plume lasting 3-15 µsec7. Over-corrections are more likely in dry conditions and vice
versa8.
Laser Fluence Other Considerations in Lasik
Laser fluence is described as the amount of energy applied Pupil Size
per unit area with each pulse (mJ/cm2). The minimum Laser should be planned in such a way that the Functional
fluence necessary for proper photoablation of the cornea is Optic Zone (FOZ) should be more than the mesopic pupil
approximately 50-60 mJ/cm2. It should be checked before size. FOZ is 25% less than the ablation diameter. Larger
every ablation, which is usually performed automatically pupil diameter requires a larger ablation zone otherwise it
in most laser delivery systems. The two factors affecting can give rise to significant glare post-operatively. However,
fluence are gas pressure and voltage. Low fluence means modern LASIK has negated the role of the low light pupil in
that the gas concentration should be raised to avoid under predicting adverse visual outcomes after LASIK outside of
corrections. the early postoperative period9.

56 l DOS Times - Vol. 20, No. 7 January, 2015

Refractive Surgery

Figure 1: Myopic Ablation Profile. Figure 2: Hyperopic Ablation Profile.

Figure 3: Astigmatic Ablation Profile. angle kappa can be measured using a synoptophore or
major amblyoscope. Most excimer laser platforms centre
Optical Zone (OZ) keratorefractive procedures over pupillary axis. However,
According to the Munnerlyn’s formula, the depth of ablation in cases with a large angle kappa (hyperopes), there is
is directly proportional to the square of the diameter of the a greater chance of decentred ablation because of the
OZ. For example, reducing the OZ from 6mm to 5mm, increased distance between pupillary axis and visual
induces a reduction of nearly 30% of the maximal depth of axis. Decentred ablation can lead to a number of visual
ablation. This can allow full correction of high myopic errors complaints including glare, distortion, reduced visual
in patients with relatively thin corneas. The disadvantages acuity, and diplopia. Thus, accurate centration of the
of an excessively small OZ include poor optical quality and ablation zone during laser vision correction is essential
increased risk of regression10. For an ablation zone of 6.0 for optimal outcome. Excimer laser systems allow for the
mm, a conventional myopic correction would be expected movement of the ablation centre away from the pupil
to remove approximately 12 μm/D of correction. centre with an offset by entering either X and Y Cartesian
Angle Kappa in Refractive Surgery or R and Ɵ polar values. Large angle kappa should also be
The exact definition of angle kappa is the angular distance considered before using a wavefront-guided treatment as
between visual and pupillary axis. Clinically, the angle wavefront is currently calculated centered on pupil. The
kappa was redefined as the angular distance between the relatively small degree of angle kappa in myopic eyes and
line of sight (line connecting the pupillary centre and the the larger optical zone in myopic ablation compared to
fixation point) and the pupillary axis (Figure 4). The exact hyperopic ablation makes myopic ablation less sensitive to
decentration11.
Custom Ablation
The linking of the laser device to various instruments
allows for correction of irregular (eccentric) ablations and
high-order aberrations. Few of the customized ablation
procedures include:
Wavefront-optimized ablation profile: In addition to treating
lower-order aberrations, wavefront-optimized treatments
attempt to maintain the preoperative prolate shape of the
cornea by removing more stromal tissue peripherally than
in conventional treatments and adjusts for postoperative
biomechanical and biologic effects.
Wavefront-guided ablation profile: Wavefront-guided
treatment is customized ablation that attempts to reduce
the optical aberrations and the total wavefront error of
patient’s eye to a reference ideal. The input data are more
complex and time consuming to measure as it is derived

www. dosonline.org l 57

PG Corner: Principles of Kerato-Refractive Surgery

Figure 4: Angle kappa. Q-factor adjusted ablation profile (F-CAT): This approach
is based on refractive error and corneal topography
from objective wavefront sensors (e.g. Hartmann–Shack measurements, and the resultant laser ablation profile
sensor and Tscherning aberrometer). It ablates deeper into corrects the refractive error, while trying to produce a
the stroma compared to conventional treatments. more aspheric corneal shape. The target corneal contour
Topography-guided ablation profile (T-CAT): Topography for reducing spherical aberrations is calculated as having a
- guided ablations are an alternative treatment option Q-factor of −0.40. The major advantages of this technique
for patients with irregularities of the corneal surface like compared to wavefront-guided treatments are that it is
keratoconus. A major limitation of this technology at this less time consuming and produces a clinically equivalent
time is that it does not correct refractive spherical error; reduction in certain postoperative optical aberrations to
therefore, a two-stage keratorefractive procedure has been wavefront-guided ablations. Its disadvantages are that
proposed where a topography-guided treatment is followed it ablates more tissue centrally than wavefront-guided
by a wavefront-guided treatment. treatments and does not correct all higher-order aberrations
as it predominantly corrects spherical aberrations, similar
to wavefront-optimized ablations.
Relex/ Smile Refractive Procedures
These are keratolenticular refractive procedures in which
femtosecond laser can be used to carve out a lenticule
within the corneal stroma. The lenticule can then be
extracted from within the corneal stroma, either by creating
and lifting a hinged flap or by extricating it using a small
incision in the cornea. These techniques of femtosecond
lenticule extraction are known as femtosecond lenticule
extraction (FLEx) and small-incision lenticule extraction
(SMILE), respectively. These techniques have the advantage
of all-in-one femtosecond laser procedure. They represent
novel integrated surgical techniques to perform corneal
laser surgery in a single step needing only one laser to
perform laser refractive surgery and have various clinical,
practical, and economic advantages over the more
traditional two-laser solution12.
References

1. Choi YI, Park SJ. Corneal flap dimensions in laser in situ keratomileusis using the
Innovative automatic microkeratome. Korean J Ophthalmol 2000;14:7-11.

2. Yi WM, JooCK. Corneal flap thickness in laser in situ keratomileusis using an
SCMD manual microkeratome. J Cataract Refract Surg 1999;25:1087-92.

3. Solomon KD, Donnenfeld E, et al. Flap thickness accuracy: comparison of 6
microkeratome models. J Cataract Refract Surg. 2004;30:964-77.

4. Donnenfield E, Solomon K, Perry HD, et al. Effect of hinge position on dry eye
signs and symptoms following LASIK. Ophthalmology 2003;110:1023-29.

5. Seiler T, Kofala K, Richter G. Iatrogenic keratectasia after laser in situ
keratomileusis. J. Refract. Surg. 1998;14:312-17.

6. Ratkay-Traub I, Ferincz IE, Juhasz I, et al. First clinical results with the
femtosecond neodymium glass laser in refractive surgery. J. Refract. Surg.
2003;19:94-103.

7. Puliafiti CA, Stern D, Krueger RR, et al. High-speed photography of excimer laser
ablation of the cornea. Arch Ophthalmol 1987;105:1255-59

8. De Souza IR, de Souza AP, et al. Influence of temperature and humidity on laser
in situ keratomileusis outcomes. J Refract Surg 2001;17:202-205

9. Myung D, Schallhorn S, Manche EE. Pupil size and LASIK: a review. J Refract
Surg 2013;29:734-41.

10. Freedman KA, Brown SM, Mathews SM, et al. Pupil size and the ablation zone
in laser refractive surgery: considerations based on geometric optics. J Cataract
Refract. Surg. 2003;29:1924-31.

11. Park CY, Oh SY. Measurement of angle kappa and centration in refractive
surgery. Curr Opin Ophthalmol. 2012;23:269-75.

12. Kim JR, Hwang HB, Mun SJ, Chung YT, Kim HS. Efficacy, predictability, and
safety of small incision lenticule extraction: 6-months prospective cohort study.
BMC Ophthalmol. 2014;3:14:117.

58 l DOS Times - Vol. 20, No. 7 January, 2015

Monthly MeReetfirancgtivCe Sourrngeerry

Retained Intraocular Bhartendu Varma
Foreign Body DNB, FICO

Bhartendu Varma DNB, FICO, Nidhi Panwar MD, FNB, S.N. Jha MD
Department of Ophthalmology, Sir Ganga Ram Hospital, Rajender Nagar, New Delhi

Intraocular foreign bodies represent up to 41% of all open We report a case of a young male who presented to us
globe injuries1-3. While foreign objects can be composed within 1 hour of a hammer-chisel injury.
of almost any substance, most common are metallic, as the Case Report
majority of patients are injured while welding or hammering. A 29-year old male presented with chief complaint of pain,
Intraocular foreign bodies (IOFBs) may become embedded photophobia, watering of left eye since 1 hour following
in any ocular structure, from the anterior chamber to the trauma. There was history of injury to the eye while working
retina. 75% of the IOFBs lodge in the posterior segment4. with hammer & chisel. The patient was evaluated for any
Retained intraocular foreign bodies most commonly result other injuries apart from the ocular trauma. Prophylaxis
from occupational activities and predominantly involve against tetanus was given.
males in 3rd to 4th decade5. On ocular examination the patient had visual acuity of 6/9
There is an increased risk for endophthalmitis and toxicity in right and 6/9P in the left eye. There was a self-sealed
by the IOFB material, as well as other considerations
specific to its surgical removal. Figure 1: Self-sealed full thickness linear
When a patient presents with an open globe injury, a penetrating wound.
complete history is essential in establishing a diagnostic and
therapeutic plan. First, any life-threatening injuries should
be assessed and treated appropriately, particularly because
of the risk of associated head trauma. Check and document
the visual acuity and relative afferent pupillary defect. The
measurement of intraocular pressure should be deferred if
there is a large laceration or concern for a ruptured globe.
It is not uncommon that, in cases of small projectile foreign
bodies, such as those associated with hammering, the entry
wound is small and can be self-sealing.
Investigations that can be done in case there is doubt, are
as follows:
• CT scan with thin slices - gold standard
• B-scan Ultrasonography - sensitivity is user dependent.
• Plain X-ray orbits - screening modality.
• MRI contraindicated in suspected metallic IOFBs.
Management protocol may vary according to the time of
intervention which may be early or delayed.

www. dosonline.org l 59

Monthly Meeting Corner: Retained Intraocular Foreign Body

Figure 3

Figure 2: Sectoral iris defect with D shaped
pupil with localized inferior lenticular opacity..

full thickness linear penetrating wound on the cornea of Figure 4
left eye from 4 to 6 o’clock hours, approximately 3x1 mm
(Figure 1). intraocular foreign body with grade 1 Visual acuity without
The anterior chamber was of normal depth, cells as per RAPD involving Zone 1 and an OTS Raw Score of 77 and
SUN group classification was 3+ and flare was 1+. The an OTS score of 3. On the basis of the OTS score we were
pupil was D shaped (Figure 2) with sluggish reaction and able to counsel the patient about the prognosis and the
there was no RAPD. Sectoral full thickness iris defect at 4 risks, along with the need for surgery.
to 5 o’clock hour was observed. This made our index of Initial management was started, patient was given Inj.
suspicion high for a retained intraocular foreign body. Ceftriaxone 1gm IV, mannitol infusion 350 ml IV over
Anterior subcapsular opacity was appreciated inferiorly, as 45 mins, Tab. Acetazolamide 2 tab stat, moxifloxacin and
seen through the full thickness iris defect. homatropine 2% eye drops were instilled and the eye was
On fundus examination media were clear glow was present, patched.
disc was normal, a foreign body, floating in vitreous cavity
was visualized (Figure 3). Macula was normal (Figure 4).
We performed a siedel test which was negative, the
Intraocular pressure was 35mm with Tonopen. Right eye
examination was within normal limits.
CT scan orbits were done which showed an Intraocular
foreign body measuring 2.8x1.8mm (Figure 5).
We made a diagnosis of left side self-sealed full thickness
corneal penetrating injury with traumatic cataract with
retained intraocular foreign body. As per Ocular Trauma
Classification Group Left Eye Open globe injury with

60 l DOS Times - Vol. 20, No. 7 January, 2015

Refractive Surgery

Figure 5: CT Scan

Figure 6: Posterior capsular defect from 4-6 o’clock. Corneal perforation repair was done with 10-0 ethilon. A 23
G trocar entry was made inferotemporally to lower down
The patient was NPO for the past 5 hours when he the pressure, it was plugged during phacoemulsification.
presented to us, so we planned for an urgent surgery and Clear corneal temporal phacoemulsification was carried out
our plan being: with low fluidic parameters. After removal of the nucleus
• Repair of corneal perforating injury a posterior capsular defect (Figure 6) was identified in the
• Phaco-aspiration ± IOL Implantation inferotemporal area at 4-6 clock hours corresponding to the
• Pars plana vitrectomy with endolaser with removal of iris defect (highlighting the path of the foreign body).
The corneal wound (made for phacoemulsification)
intraocular foreign body ± silicone oil injection was sutured with 10-0 Ethilon. Ports for 23 Gpars plana
• Intravitreal Antibiotics (Vancomycin + Ceftazidime) vitrectomy were made, anterior vitrectomy was carried
out.The foreign body which was floating had lodged into
under GA with guarded visual prognosis. the retina and had created a retinal break with a localized
detachment (Figure 7).
A complete vitrectomy was carried out along with removal
of vitreous and its adhesions surrounding the foreign body,
with induction of PVD with the help of tricort (Figure 8).
A separate sclerotomy was made superotemporally with
the help of MVR blade measuring around 3 mm at 4mm
from limbus (Figure 9).
23 G ILM forceps was introduced through the separate
sclerotomy and the foreign body was grasped& removed
through the sclerotomy. The foreign body measured
3x2mm approx (Figure 10).
Fluid air exchange was done through the retinal break.
Retinal photocoagulation was done along the retinal break,
3 rows of laser barrage was done in the periphery. Silicon
oil was injected. Scleral ports were closed with 8-0 vicryl.
Post-operatively the patient was started on Prednisolone
acetate e/d 8 times/day, moxifloxacin e/d 4 times/day,

www. dosonline.org l 61

Monthly Meeting Corner: Retained Intraocular Foreign Body

Figure 7: Foreign body lodged into the retina
alongwith localized detachment.

Figure 9: Separate Sclerotomy for removal of IOFB.

Figure 8: Induction of PVD, assisted by Triamcinolone acetonide
and 23 G Backflush Cannula.

homatropine e/d 3 times/day, brimonidine + timolol Figure 10: Removed Intraocular Foreign body.
(combination) e/d 2 times/day, tab Ofloxacin 200 mg 2
times/day. Discussion
On 1st post-operative day VA was 2/60 with an IOP of 19 Classification of Open Globe Injury
mm Hg. (Figure11) 1. Type of injury
At 2 weeks post-operative BCVA was 6/24 A. Rupture
(+4.00/+4.00x180º), IOP was 16, retina was attached. B. Penetrating
At 5 weeks follow up BCVA was 6/24P , localized epiretinal C. Intraocular foreign body
membrane was seen along the inferior vascular arcade D. Perforating
superior to the site of retinal break. (Figure 12) E. Mixed
Further plan of management 2. Grade based on V/A at initial examination*
1st Stage- Silicon Oil removal with ERM peeling with Grade 1: greater or equal to 20/40
C3F8 injection.
2nd Stage- SecondaryIOL implantation

62 l DOS Times - Vol. 20, No. 7 January, 2015

Refractive Surgery

Figure 11: 1st POD fundus picture with lasered retinal break.

Grade 2: 20/50 – 20/100
Grade 3: 19/100 – 5/200
Grade 4: 4/200 – light perception
Grade 5: no light perception**
3. RAPD
Positive: RAPD Present
Negative: RAPD absent
4. Zone of injury***,based on location
Zone1: Isolated to cornea (includingcorneo-scleral

limbus).

Ocular Trauma Score (OTS)

Initial Visual Factor Row Points

A Initial visual acuity NLP - 60 Figure 12
category LP to HM- 70
1/200 to 19/200- 80 Zone 2: Limbus to 5mm posterior into the sclera.
20/200 to 20/50- 90 Zone 3: Posterior to anterior 5mm of sclera.
>20/40- 100 Timing of Primary Repair
-23 The wound should be closed as soon as possible. Delay in
B. Globe rupture -17 closure could increase not just the risk of infection but also
-14 the opportunity for an expulsive hemorrhage and extrusion
C. Endophthalmitis -11 of intraocular contents. Systemic and topical antibiotic
-10 therapy should be started as soon as possible. Tetanus
D. Perforating injury prophylaxis should never be forgotten.

E. Retinal detachment

F. Afferent papillary
defect (Marcus Gunn
pupil)

Raw score sum-sum of raw point

www. dosonline.org l 63

Monthly Meeting Corner: Retained Intraocular Foreign Body

Row Score Sum OTS Sum NLP LP/HM 1/200-19/200 20/200 to 20/50 > 20/40

0-44 1 73% 17% 7& 2% 15%
45-65 2 28% 26% 18% 13% 44%
66-80 3 2% 11% 15% 28% 74%
81-91 4 1% 2% 2% 21% 92%
91-100 5 0% 1% 2% 5%

Vitreous Magnetic Visualised Non-Visualised
(unimpacted, no Ext. Magnet/ vitrectomy Vit, Forceps, Magnet
evidence of retinal
injury) Vitrectomy, Forceps Vit, Forceps
Non magnetic, unimpacted. Non Trap Door/ Vitrectomy, Forceps Trap Door/Vitrectomy, Forceps
Intraretinal Magnetic and
Magnetic

Early removal of the IOFB at the time of primary repair • For nonmagnetic foreign bodies proper forceps are
has the following advantages: Single procedure, decrease used.
in endophthalmitis rate, decrease in PVR rate. Many
studies suggest that early Vitrectomy and removal of • Following IOFB removal, a thorough peripheral
IOFB decreases the risk of infectious endophthalmitis and Vitrectomy should be performed, and posterior hyaloid
proliferative vitreoretinopathy. Unless the IOFB is removed should be removed.
and the wound repaired within 24hrs the patient’s risk of
severe complications – such as endophthalmitis or vision References
loss – quadruples. Delay in IOFB extraction, presence of
intraocular hemorrhage, preoperative retinal detachment 1. Cazabon S, Dabbs TR.Intralenticular metallic foreign body. J.
are the predictive factors for anatomic failure (postoperative Cataract Refract Surg. 2002; 28: 2233-4.
retinal detachment is considered as the anatomic failure).
Good initial presenting VA, early surgical intervention to 2. Arora R, Sanga L, Kumar M, et al.Intralenticular foreign bodies: report
remove IOFB (within 24 hours) and PPV are predictive of eight cases and review of management. Indian J Ophthalmol.
factors for good visual outcome. 2000; 48: 119-22.
Surgical options
• Vitrectomy and removal of IOFB by magnet or forceps. 3. Coleman DJ, Lucas BC, Rondeau MJ, et al. Management of
• Un-impacted ferrous IOFB - strong intraocular magnet. intralenticular foreign body. Ophthalmology. 1987; 94: 1647-53.

4. Dhir SP, Mohan K, Munjal VP, et al. Perforating ocular injuries
with retained intra-ocular foreign bodies. Indian JOphthalmol.
1984;32:289-92

5. Behrens-Baumann W, Praetorius G. Intraocular foreign bodies. 297
consecutive cases. Ophthalmologica. 1989; 198: 848.

64 l DOS Times - Vol. 20, No. 7 January, 2015

DOS Times Quiz Delhi
Ophthalmological
Society

Instructions:

1. Please return your answers to [email protected] or mail them to “The Quizmaster, DOS Times Quiz,

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2. The answers should reach not later than 31th March, 2015.

The quiz can also be viewed and directly answered on our website www.dosonline.org

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will be given a prize of Rs. 2,500. If there are more than one correct entries, the winner of the prize will be decided by

draw of lots. Quiz compiled by Dr. Parul Jain

1. Identify the complication seen after refractive 2. Identify the complication.
surgery.

3. Identify the IOL? 4. What is the thickness of Implantable contact
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