DOS_oct_2009

Contents

E5 ditorial Neuro-Ophthalmology

Focus 57 Third Cranial Nerve Palsy

7 Common Problems during LASIK Surgery: How to solve them? J.L.Goyal, Sudha Seetharam, Ritu Arora

Retina Glaucoma

25 Central Serous Chorioretinopathy 61 Ganglion Cell Comlex: A Newer Diagnostic Aid in

Priyank Garg, Syed Asghar Hussain, S.K. Gupta, S.K. Garg, Pre-Perimetric Glaucoma
Gagan Bhatia, S. Natarajan Suneeta Dubey, Baswati Prasanth, Monica Gandhi, Julie Pegu,
Parmod Kumar
Cornea
Clinical Monthly Meeting
37 Pentacam: A Step Forward in Anterior Segment in Diagnostics
67 Clinical Talk -Management of Posterior Capsular Tear:
Amruta Padhye, Sujatha Mohan, Mohan Rajan
A Vitreo-retinal Surgeon’s Perspective
Refractive Surgery Neeraj Manchanda, S.N. Jha, Amit Khosla, H.K. Tewari,
Tinku Bali, Nidhi Tanwar
49 Pre-operative Evaluation for LASIK
A71 bstracts
Ranjan Dutta, Dariel Mathur, Yamini Kaushal
Columns

77 Membership Form

Attention DOS Members 3

All DOS members less than 35 years are invited to write for
DOS Times. Best five articles will be selected, and the first
author(s) will be invited as speakers at the Annual Conference on

17th and 18th April 2010 at Hotel Ashok.

www.dosonline.org

Editorial

My Dear Friends and Colleagues,

The midterm DOS conference is over, and suddenly we are halfway through this year. I hope you
enjoyed your time at the conference and benefited from it.

What makes a conference successful. (I wonder, and perhaps I can foretell; looking at the amount of
conferencing going on-change is in the offing. Someon , somewhere; is going to get this brainwave and start
rating the conferences. Some thing, like the TRP ratings. Sponsors and delgates will consider the TRP
ratings, before participation!)

Coming back to the question, “What makes a conference successful”? I want to start this debate and I invite your views. I wish
to publish the new, and the useful, and the radically creative ideas in the DOS times. Let us have a lively debate. Let us have a
flood of ideas and a fiery brainstorming.

Is it the academic content, the hands on workshops and the live surgery and the oratorical skills of the speakers. Is it the trade
exhibition and the display of technology, (exorbitant and overpriced; often beyond the reach of the average Ophthalmologist).
Is it the ambience, the food and the cultural programmes and events for the pleasant evenings. Is it the brand image of the
conference, the society organizing it and the big names associated with it ;providing the all important snob value. Is it the venue:
5 star or more; or the place-say a pretty hill station or a touristy beach town or even better: a cruise ship conference. Or is it –
all of them or something else all together that I have missed. It is that something else that I want you to tell me. To let me know. To let
all of us know.

It is well known that Cataract Surgery and many other eye surgeries do not require overnight stay in the hospital. Most of the
Cataract Surgeries done globally are ambulatory OPD procedures. High time therefore, that the Ophthalmology Clinics and Day
Care Centre, be recognized by the Delhi Govt. The Delhi Ophthalmological Society is trying hard to get it done. I request all
members to use their reach and influence, and the goodwill they have gained after so many years of hardwork. We can only get
this done by lobbying hard with the lawmakers. This issue affects each and everyone of us and let us throw aside all complacence
and do it together. Ophthalmology is a day care subspeciality, and it is a well known fact. This fact must be officially recognized,
and only with our constant, diligent efforts can we achieve this goal.

Thanking you,

Dr Amit Khosla
Secretary,
Delhi Ophthalmological Society

www.dosonline.org 5

Common Problems during LASIK Surgery: Focus
How to solve them?

Sujal Shah, DNB Neera Agarwal, MS, MBBS Anuj Kumar Singh, MD, MBBS

LASIK (Laser Assisted in Situ Keratomileusis) is a term used for correcting refractive errors and astigmatism by using laser.
The technique of Keratomileusis was developed by Jose Barraquer, who developed the first microkeratome, and developed
a technique to cut thin corneal flaps and alter its shape. Later the introduction of lasers in refractive surgeries rose from
Srinivasan’s work, who in 1980, discovered that Excimer laser could alter the living tissue in a precise manner with no
thermal damage to the surrounding area. Since then, this technique of LASIK has undergone tremendous amount of
change but, still there are a number of problems that the young surgeons face while carrying out this procedure. Here, we
questioned some of our pioneering refractive surgeons to throw some light on LASIK surgery related problems.

(SS): Dr, Sujal Shah, DNB, Cornea & Refractive Surgeon, Samyak Drishti Eye Centre, N.S. Patkar Marg, Mumbai,
Maharashtra, Visiting Asst. Prof. Jules Stein Eye Institute-UCLA, Los Angeles, USA

(NA): Dr. Neera Agrawal, MS, MBBS, Neera Eye Centre Neera & Laser Vision 91-B, Shyamlal Road (Opp. Hindi
Park), Daryaganj, New Delhi, India

(AKS): Dr Anuj K. Singh, MD, Laser Eye Clinic, Derawal Nagar, Delhi; India, Member American Society of Cataract
and Refractive Surgery.

(AC): Dr Ashima Chandra, DNB, Consultant, Sir Ganga Ram Hospital, Rajinder Nagar, New Delhi.

AC: What is the cut off K-reading? NA: The maximum Posterior float on Orbscan should not be >
50 microns and on Pentacam it should not be more than 25
SS: 48D micron. The readings above 40 micron on Orbscan and 20
micron on Pentacam are suspicious. Though, final decision
NA: When you are planning to do lasik in a patient, it is very should be made only after seeing all the maps on the screen,
important to know what would be the final K reading in a including a pachymetric map.
patient after lasik. The flattest K reading after Myopic lasik
should not be less than 37D and for a hyperopic Lasik AKS: 0.040 mm in younger patients, can stretch a bit in patients
steepest K should not be more than 48D. That means you over 30 years.
could correct more myopia if the K readings were steeper
and more hyperopia if the K readings were flatter. One AC: Max correctable refractive error in a patient?
should not perform Lasik in a patient with pre-operative
K-readings of 45 and above because of high suspicion of SS: 12D (depending on pupil size, pachymetry, flap thickness,
Keratoconus even in absence of definite signs of corneal topography).
keratoconus.
NA: The results for correction of > -10 D myopia and > +6 D
AKS: 37 D to 47 D. Beware of small + flat and large + steep hyperopia are unpredictable and prone to complications.
corneas. Hence these corrections are to be discouraged. Maximum
correctable error will also depend on pre-operative K
AC: Max post float on Orbscan and Pentacam readings.

SS: Don’t currently use Orbscan or Pentacam. But, probably AKS: + 6 D to – 10 D is a reasonable range. Beyond these the

elevation of 10-20 microns. image quality deteriorates.

www.dosonline.org 7

AC: Consideration for pupil size? The most common place to locate a missing flap is underside
of the keratome.
SS: Scotopic pupil size and pachymetry such that a treatment
diameter of approx 6mm can be used. Once you have located the flap you should put it on stromal
bed. Most of the times if you put the flap on the stromal
NA: Any pupil more than 6.5 mm will lead to considerable night bed you will be able to make out which side is epithelial
vision problems. In such patients one should discourage because the flap tends to take the shape of cornea. You
lasik especially if they are also involved in night driving. must remember that you can never attach epithelium on
stromal side, so once the flap is securely in place ,there is no
AKS: Wavefront guided or optimized treatment would be need for you to worry.
desirable for larger pupil size as the effective optical zone
has to overlap the scotopic pupil by at least 1 mm. A blend AKS: 1. If the flap is in place and properly oriented – hinge the
zone, wherever possible, makes life easy for everyone. A flap with two interrupted 10-0 monofilament sutures
large pupil not only causes night vision problems; it also at 11 – 1 o’clock and proceed. Suture removal after 5
results in more induced higher order aberrations. Using days.
Customvue AND a blend zone in VISX, we try to provide
the benefits of both customized and optimized treatments 2. If the flap is subluxated but still on the eye, drag it
in large pupil eyes. sideways with two instruments to get enough clear
space for ablation. After ablation the flap is to be
Very small pupils are difficult to track. dragged back onto the bed and a bandage lens applied.

AC: How to deal with small palpebral aperture? 3. If the flap is on the keratome, it should be secured
carefully and kept in BSS. After ablation it is put back
SS: Different ring size, lignocaine jelly, lateral canthotomy, avoid using the asymmetric marks on the cornea to correctly
speculum. orientate the anterior – posterior faces. The epithelial
side is smooth and will not go down well on the stromal
NA: One of the most common problems faced during Lasik is bed. The stromal side is granular and will settle easily.
that of small palpebral aperture. For such patients, it is Never suture the flap where the anterior posterior
wise to have a speculum with a tight screw so that it does orientation is in doubt. A free flap on a astigmatic
not give way in case the patient squeezes the eye during cormea is toric in configuration and will induce
making of the flap. The other trick would be to rotate the astigmatism if put back with a rotational error.
speculum with your ring finger along with the movement
of the keratome. AC: How to manage incomplete flap?

AKS: Use narrower footplates on the suction if available SS: Abort procedure on same day and treat after 2 – 4 weeks.
[tradeoffs → more decentration and suction loss]. Open
wire speculum instead of solid blades. Canthotomy or PRK NA: To avoid incomplete flap from happening you must do the
in desperate situations. dry run on the suction ring to see how for the keratome
must go for complete flap. Let this be a reference point for
AC: How to avoid suction loss during flap making? you to use while making a flap on cornea.

SS: Keep talking with patient to relax them and prevent Moreover incomplete flaps are more common in case of
squeezing. narrow palpebral aperture where full range of movement
of keratome is not possible. Whenever you have an
NA: It is very important to check IOP with applanation after incomplete flap, you must make an estimate whether it will
securing the suction ring in place. Other important method allow ablation or not. In case ablation is not possible, one
is to release the hold on the ring to see if it stays in place. should abandon the procedure and repeat the flap one
Most of the time problem arises if there is too much month later.
conjunctival tissue between the cornea and the suction ring,
which tends to swell up and the ring pressure is not applied AKS: If we get a 6mm oz clear, proceed with treatment protecting
in the proper place. the hinge to prevent double ablation. If the flap is well
centred but not giving adequate clearance, try to rectify the
AKS: Avoid repeated applications of suction ring and twisting error [mechanical block, break in vacuum line, electrical
movements of the ring once the suction is on. Beware of disconnection], then IMMEDIATELY put the suction ring
pterygia, pingueculae, filtering blebs, scleral buckles etc. into the original conjunctival groove and make a second
pass. The blade will go into the first cut. If the keratome
AC: How to manage a free flap? cannot be set right immediately or the flap is badly centred,
it is better to wait 3 weeks and do a surface procedure.
SS: If diameter is large enough to permit treatment, go ahead
and treat same day and can be realign flap as per preop AC: How to manage a button hole?
marking and use BCL.
SS: Realign the flap carefully. Rpt procedure after 2-4 weeks.
NA: It is very important to remember that this complication will
always be seen by all lasik surgeons in their lifetime. If you NA: If you have a button hole it is important not to proceed
have a free flap you should remember following things. with the ablation, otherwise you will end up with bad corneal

8 DOS Times - Vol. 15, No. 4, October 2009

haze. Flap with Button hole should be replaced and a new AKS: Steamy cornea under the flap with fluid accumulation at
flap should be made 1 month later. There are higher chances the interface. Unexplained sudden regression of the
of button hoe in very steep corneas, so one has to be careful refractive correction.
in these cases.
AC: Regression – when to treat?
AKS: Abort procedure as soon as button hole is seen. Put flap
back in place with least possible disturbance. Bandage lens. SS: When the following criteria are met to exclude primary
Following stabilization of the activated stromal keratocytes undercorrection.
and epithelial remodelling [3 – 4 weeks], a trans-epithelial
PTK or PRK with Mitomycin can be done. a. initially the correction was accurate / stable at 6-8 weeks
postop.

AC: How to manage debris under the flap? b. there is a change in the refraction from the correction
achieved at 6-8 weeks.
SS: If signoificant, lift flap and re-rinse.
c. If the patient is symptomatic
NA: Common debris seen under the flap is meibomian
secretion, cotton fibres, pieces of eye lashes. It is very d. If ectasia can be ruled out
important to wash the undersurface of the flap carefully to
remove all the debris. Patient should be examined on slit e. If there is adequate pachymetry available for
lamp immediately after surgery for evidence of debris under retreatment
the flap. In case some debris is present it should be
immediately taken care of. NA: When to treat regression – at least 2 repeat refractions at
one month apart should be the same, in case you are
AKS: Evert flap and loosen debris with a dripping wet sponge. considering re-teatment.
Wash with smooth laminar flow.
AKS: At least 3 months post surgery in myopes and 1 month in
AC: How to manage DLK? hyperopes.

SS: Early stage, medical management with steroids. If it does AC: Which powers?
not clear re-lift flap and rinse.
SS: Any power low or high if it is symptomatic and makes a
NA: DLK or Diffuse Lamellar Keratitis is the interface visually significant difference to the patient, provided safety
inflammation seen in some case after Lasik. The best way is is not compromised.
to start on 1 hourly strong steroids like Prednisolone
Acetate. However there is no role of systemic steroids. In NA: How to evaluate –Pentacam or Orbscan are a must to
case it does not resolve with steroids, one may need to lift evaluate posterior float.
the flap and wash the undersurface. But one must
remember that every repeat procedure predisposes to AKS: Apparent overcorrections can be very misleading. Always
repetition of DLK. So lifting of flap should be the last resort confirm under cycloplegia.
when everything else has failed.
AC: How to evaluate patient with regression?
AKS: Topical steroids, gentle wash of interface with warm Ringer’s,
topical acetylcysteine [5%-10%, to prevent stromal lysis], SS: Chk posterior corneal elevation on Pentacam or similar
Polymyxin eye drops [endotoxin binders]. Frequent follow device to exclude iatrogenic.
up.
NA: How to treat – In most cases old flap can be re-lifted even
AC: When to suspect raised IOP? 2 -3 years after first Lasik. But in case old flap can not be
lifted one can go for a fresh flap. The only problem that is
SS: In the presence of interface fluid, ie a clear space between encountered with fresh flap is wedge resection which should
the flap and bed, postoperatively. be replaced with the flap.

NA: Contrary to normal belief, quite a few patients will show AKS: Posterior float and keratometric maps are a must and
response to mild steroids like Flourometholone. It becomes should be matched with preoperative data whenever
difficult to diagnose because these patients present with possible. Induced cylinders merit a meticulous slit lamp
either collection of fluid in the interface and appearence of examination. A wavefront analysis and OCT to evaluate
a cleft between host and stromal bed. Sometime the picture flap thickness are desirable though not mandatory.
is almost indistinguishable from DLK and you treat them Adequate thickness is essential for a retreatment.
with frequent steroids and the condition worsens. As a rule
if any DLK is worsening one must check intra-ocular AC: How to treat ( same flap/ new flap)?
pressure. Sometimes if there is formation of a fluid cleft,
the pressure measured may appear to be within normal SS: If relaiable data regarding flap thickness and residual stromal
range but the classic picture must alert you to raised IOP. It bed is available, relift the same flap. If no relialble data-
is to be managed with anti-glaucoma medication and history or investigations such as OCT are available, then
stopping steroids. new flap that is the thinnest possible.

NA: Most of the times there are no complications with re-
treatment but one must note that there is a higher chance
of developing epithelial down-growth with re-treatment.

www.dosonline.org 9

AKS: Relift 1st choice, surface ablation 2nd choice, recut 3rd choice. area to prevent regrowth. The cell nest can be scraped off

Establishing the hinge orientation is of paramount with a smooth spatula. The epithelium on the fistula site

importance in relifting. should be recessed away from the flap margin towards the

AC: Complications with re-treatment? limbus [like we recess the conjunctiva away from the limbus
after pterygium surgery]. Suture the flap at the fistula site.

SS: 1. Epithelial ingrowth Too tight suturing would cause gaping of the margin
2. Ectasia alongside, creating fresh fistulas. Finally a bandage lens to
keep things settled. In extreme cases where the entire flap

AKS: Torn flap and epithelial ingrowth in relifting, stromal haze is compromised, it would be wiser to sacrifice the flap and
in surface ablation [mitomycin desirable], intersection of do a PTK of the bed.

flaps with loose wedges of tissue in recutting. AC: How to manage post lasik infective keratitis

AC: How to manage epithelial downgrowth – when to treat? SS: 1. Appropriate antibiotic after culture and sensitivity

SS: a. Treat aggressivley early, if found to be progressive 2. If no specimin available lift flap, take material for
b. Re-lift flap and scrape carefully and completely microbiology, rinse with fortified antibiotic and institute
c. If it recurs repeat above appropriate medical therapy, including rinsing of interface
if necessary

d. If recurrent-repeat above and perform 5-10 mic PTK 3. If unresponsive, the part of the flap that is involved in the
to address any residual cells infiltrate maybe judiciously amputated.

NA: Small amounts of epithelial Down-growth is very common NA: Post Lasik infections have very varied presentations, most
in cases of Lasik. Fortunately, it is limited to flap margins of the times the infiltrates tend to tickle down in the area of
and is of no consequence. It looks like a scar on flap margin. interface. During the treatment, one may need to sacrifice
In case there is progression in epithelial downgrowth ,flap the flap. Therefore, post Lasik infective keratitis is to be
should be cleaned and replaced. During scraping of aggressively managed. In case there are infiltrates on the
epithelium, one should take care to clean the under surface surface, it better to scrape and culture and treat accordingly.
of the flap also. One may need to put sutures sometimes at
the site of entry in case you feel that flap does not adhere AKS: 1. Early onset [1st week] Mostly Staphylococcal - Fortified
properly. Vancomycin 50 mg /ml [5%], Gatiflox 0.3% or Moxiflox
0.5%, fortified Cephazolin 50 mg / ml [5%]. Can use
AKS: Anything more than a mm inside the flap margin. these to wash the interface in addition to eye drops.

AC: How to treat? 2. Late onset [after 10 days] Mostly Atypical Mycobacteria-
branching filamentous Gm + rods] – gas bubbles and
AKS: Accidentally implanted epithelial cells in the interface die cracked windshield appearance are useful clues.
off. 99 % of Epithelial ingrowth is linked to the epithelial Fortified Amikacin 35 mg /ml [3.5%], Fortified
stem cells of the peripheral cornea; a fistula of epithileal Cephazolin [5%], Gati / Moxi in usual concentrations.
plug being the umbilical cord. It is essential to target this

DOS Correspondent
Ashima Chandra DNB

10 DOS Times - Vol. 15, No. 4, October 2009























Central Serous Chorioretinopathy Retina

1,2Priyank Garg MS, 2Syed Asghar Hussain MS, DO, 3S. K. Gupta MS, 4S. K. Garg DO ,
5Gagan Bhatia DO 2S. Natarajan DO, FRVS

Central serous choroidopathy (CSC) is one of several the RPE pump of the neighboring normal RPE. It is plausible to
chorioretinal disorders characterized by serous detachment assume that at the basis of the disease there is a more diffuse
of the neurosensory retina and / or the retinal pigment epithelium dysfunction of the RPE cells, the choroid, or both.
(RPE). CSC is one of the 10 most common diseases of the posterior
segment of the eye and a frequent cause of mild to moderate RPE dysfunction theory
visual impairment1.
When evaluating possible patho-physiologic processes at the RPE
History of the disease2,3,4,5,6 level, one needs to consider five points:7,8

• 1866 – Von graefe – first described the disease as recurrent • The intact RPE creates a barrier between the neurosensory
serous retinitis. retina and choroid.

• 1916 – Fuch’s work on the disease was appreciated and • In areas of chorioretinal scar tissue, as occurs after
additional cases seen. inflammation or photocoagulation, the pigment epithelial
diffusion barrier remains permanently destroyed.
• 1927 – Horniker – named disease as “Central Angiospastic
Retinitis” • Choroidal capillaris exert a suction on the surrounding fluid.

• 1930 - Walsh & Sloane – “idiopathic flat detachment of macula” • The intact RPE absorbs fluid in a retinochoroidal direction.

• 1930 – Gifford and Marquardt - Theory on Angioneurotic • Under certain condition, the function of the RPE is reversed,
diathesis. so it secretes in a chorioretinal direction.

• 1953 – Klien – theory on autonomic nervous system RPE damaged via immunologic infections circulatory
dysfunction. and neuronal mechanism

• 1950’s – Bennett & Maumenee – spectrum of macular ↓
disciform degeneration.
RPE secretes ions in chorioretinal direction (towards retina)

• 1955 – Bennett – “central serous retinopathy” ↓

• 1960’s – Maumenee and Gass – FA appearance of CSC. Choroidal fluid gets attracted into this area.

• 1967 – Gass – “central serous choroidopathy” ↓

Definition Strong flow disrupts the diffusion barrier in this area.

Active CSC is characterized by detachment of the neurosensory Since the defective area is so small (in the RPE), only a tiny leakage
retina caused by accumulation of serous fluid between the photo point is visible during the earliest phase of FA. Subsequently, there
receptor outer segments and the RPE in combination with is rapid increase in fluorescein stained liquid in the subretinal
monofocal or multifocal changes in the RPE. blister during the following stages of angiography. This
demonstrates the high speed and large amount of the fluid passing
Pathogenesis through the diseased area of the RPE.

The patho-physiology of CSC is still not completely under stood. Choroid dysfunction theory9,10,11
It is important to be aware of the anatomy of the choriocapillaris-
Bruch’s membrane-RPE layer. The widely fenestrated endothelium Psychogenic, pregnancy, transplantation, type A,
of the choriocapillaris allows leakage of small protein molecules raised cortisol levels
and fluid into the intercellular space. But the RPE
represents a impermeable barrier to the diffusion of fluid into the ↓
subretinal space. The RPE pump acts in a vitreous choriocapillaries
direction to keep the subretinal space dry. It is difficult to accept Adrenergic reaction causes damage to the choriocapillaries
that a single, isolated disturbance of a few RPE cells may overwhelm
↓
Department of Ophthalmology
1. L.L.R.M. Medical College, Meerut. Hyperpermeability of choriocapillaries
2. Aditya Jyot Eye Hospital, Mumbai.
↓
3. Muzaffarnagar Medical College, Muzaffarnagar
4. Sonu Eye Hospital, Shamli. RPE cell degeneration

5. Sir Ganga Ram Hospital, New Delhi ↓

Secondary changes in RPE causes leaks

↓

Serous retinal detachment

www.dosonline.org 25

The hydrostatic pressure of the fluid pooling under the detached • This is followed by detachment of the neurosensory retina in
RPE will then mechanically cause a solution of continuity in the the surrounding area. If detachment not involving the central
RPE layer with the subsequent leakage of fluid in the sub retinal macula. Patient remains asymptomatic & detachment
space and neurosensory detachment of retina. resolves spontaneously.

Three reports from France have described elevated prevalence of • If Neurosensory detachment involves the fovea- Symptomatic.
Helicobacter pylori infection in patients with CSC compared to • Metamorphopsia.
the background population (Mauget-Faysse et al; Ahnoux-Zabso • Micropsia.
nre et al: Cotticelli et al)12,13,14 • Chromatopsia.

Types

It is of 3 types :- • Central scotoma (relative).

1. Typical or Classic CSC – Seen in younger patients & causes an • Loss of contrast sensitivity.
acute localized detachment of retina with mild to moderate
loss of visual acuity associated with one or few focal leaks • Hyperopia – corresponding to anterograde displacement
seen during FFA. of fovea.

2. Chronic CSC or Diffuse retinal pigment epitheliopathy – Wide One of the most frequent complaint is transiently seeing a dark
spread alteration of pigmentation of the RPE related to the spot in the centre of visual field. The dark spot, which is the
chronic presence of shallow subretinal fluid. subjective representation of a relative scotoma in the centre of the
visual ûeld is usually most prominent in the morning immediately
3. Atypical CSC – Bullous retinal detachments usually located after awakening. Patients often report seeing it most clearly when
inferiorly. opening their eyes and looking at the ceiling of their bedroom,
presumably because the typical ceiling is bright white and
Demography unstructured. These characteristics are typical of a relative scotoma,
and like the relative scotoma produced by light (i.e. An after-
Age: It affects young to middle aged individuals 20 – 45 years of image) it fades within a few seconds, presumably because of
age. In women age tends to be higher. If age is >50 years – diagnosis the Troxler effect, a retinal function that subtracts any stationary
is seriously questioned as mostly later it turns out to be “age related background stimulus.22
macular degeneration” and “choroidal neovascularization”. 15,16
Signs
Sex: Male predominance – 8 to 10:1

Race: Commonly affects Whites, Hispanics, Asians – Japanese • Usually a small hyperopic correction can be improved
mostly. African- Americans are affected very less. Severe form by refraction.
occurs with - south east Asian and Latin origins.
• AC and vitreous are normal.
Systemic associations of the disease17,18,19,20,21
• Fundus shows the following findings (Slitlamp
• Migraine like headache Biomicroscopy):

• Type A personality Serous retinal detachment

• Hypochondrial behavior • Round to oval well delineated shallow serous retinal
detachment is present in the macula.
• Hysteria
• This mildly darkened area is surrounded by a halo of light
• Conversional neurosis reflex and has an average size of 2 disc diameters.

• Increased Cortisol levels in patients with Cushing’s disease. • Normal foveal reflex is not apparent.

• Long term corticosteroid treatment in organ transplants & Serous detachment of RPE
Respiratory allergies.
• One or more discrete yellow to yellow grey, round to oval, well
Although the role played by corticosteroids in CSC is not well demarcated areas of detached RPE maybe observed.
understood, it is probable that among other mechanisms, the
anti- inflammatory properties of steroids may cause delayed • These areas are often present under the superior half of the
healing of the RPE defect. Cortisol, by suppressing synthesis of macular detachment when gravity forces the SR fluid
extracellular matrix components and inhibiting fibroblastic activity, inferiorly.
also may damage directly the RPE cells or their tight junctions and
may delay any reparative process in damaged RPE cells. • These detachments often less than ¼ of disc diameter in size
and have a grayish halo around them.
Symptoms
• Pigment changes maybe present on the detachments surface
• Small PEDs may be present in macular or para-macular area and occasionally are seen only on an FA.
before the onset of symptoms.

26 DOS Times - Vol. 15, No. 4, October 2009

Sub retinal precipitates • Minimal relative afferent pupillary defect may be present

• Multiple, variably sized yellow dot like precipitates probably • Reduced critical flicker-fusion thresholds

caused by SR fluid turbidity maybe noticed at the level of the • Prolonged visual evoked potential (VEP) latencies
RPE.

• Diffuse gray, white SR deposits which may represent fibrin • Dyschromatopsia

are occasionally present. • Depression of central visual field sensitivity.

• There must be a significant hyperpermeability of the After resolution,
choriocapillaris to permit such a large molecule as fibrin
(340,000 daltons) to exudate in the extravascular space. • The afferent pupillary defect and critical ûicker-fusion
thresholds are ûrst to improve
• Eventually the fibrin deposits dissolve in fibrinolysis and
disappear; however, in a few cases the deposition of fibrin in • Followed by visual acuity, VEP latency and colour
the sub retinal space stimulated sub retinal fibrosis and fibrotic discrimination.
scar formation.
• The threshold differential light sensitivity in the central visual
• This may cause permanent visual loss and may be complicated field is slowest to improve (Folk et al. 1984).
by sub retinal neovascularization or vascularization of the
fibrous scar and RPE rips. FFA

• In the fovea, a small yellow round spot maybe seen, Two types of leakages are seen23-
which maybe caused by increased xanthophyll visibility.
• Smoke stack Pattern.
Extra macular atrophic tracts
• Ink Blot Pattern.
• Gass described this as a pseudo-retinitis pigmentosa like
atypical CSC presentation with prolonged and recurrent Smoke stack pattern
serous retinal detachment.
• Seen in 7-20% (Figure 1)
• Frequent in patients of Latin and Asian ancestry.
• Also known as mushroom or umbrella configuration.
• Frequent recurrences, permanent visual loss and significant
superior visual field loss are common. • The leakage first ascends superiorly and spreads laterally.

• Yannuzzi et al: presumably, a particularly severe or prolonged • It is unknown whether the flow is caused by a temperature
leakage of fluid or both from RPE defect in SR space at the gradient or by a density gradient existing between the newly
posterior pole occurs in these patients. secreted fluid and surrounding fluid that has been in the
subretinal cavity long enough to have cooled or to have come
• The SR fluid gravitates inferiorly to form a dependant hyperdense because of preferential resorption of water and
neurosensory detachment as a flask, tear drop, dumb bell or small solutes.
hour glass pattern.
• Detachment associated with a smoke stack type of leakage is
• Sometimes the tract of SR fluid connecting the macular larger than that from an active pin point leakage.
detachment is so shallow that it is very difficult to appreciate
even with the use of fundus contact lenses. Ink blot pattern

• Seen in 93% cases

• The RPE under the chronic RD undergoes atrophic changes • Leakage point/s with uniform dye filling is appreciated.

that appear as atrophic RPE tracts connecting the posterior • Most common location – upper nasal quadrant.
pole with the dependant RD. Such RPE changes are better

noted with FA. • Least common location – lower temporal quadrant

Multiple bullous serous retinal and RPE detachment • Most leakage points are with in 1 mm of fovea but can be till
3 mm of FAZ.
• Atypical presentation
• Healthy middle aged men • In recurrent cases, leakage points is with in 1 mm of initial
• Often RD associated with SR fibrinous exudates and multiple leakage points in 80% cases

serous RPE detachment with areas of shifting SRF • Sometimes the RPED may be present superiorly than the SRD
as the fluid collects inferiorly d/t gravity.
RPE atrophic changes
Autofluorescence photography
• Corresponds to previous CSC episodes.
• Visual function and psychophysical tests • The autofluorescence characteristics of the fundus in CSC are
Functional testing of eyes with serous retinal detachment have clearly differentfrom healthy eyes24,25.
demonstrated: -
• In acute CSC, hypoflourescence has been demonstrated at
the very point of leakage (Eandi et al 2005). Acute CSC that

www.dosonline.org 27

Figure 1: Red free photograph & FFA showing Smoke Stack Pattern

has persisted for some time often shows granular or semi- • Another interesting finding with ICGA is the presence of
confluent hyperfluorescence throughout the area of multiple, “occult”, presumed RPE detachments that are imaged
detachment. with ICGA but are not noted clinically or with FA.

• In chronic CSC, irregular patterns of mixed hyper- • These areas present the typical ICGA appearance of a serous
and hypofluorescence can be seen (Framme et al. 2005; PED, namely early hyperfluorescence and late
von Ruckmann et al. 2002). hypofluorescence with a rim of hyperfluorescence.

• After reattachment, the autofluorescent subretinal deposits Indocyanine Green Angiography (ICG) of a patient with acute
disappear slowly over a period of several months. Central Serous Chorioretinopathy (CSC), the early frame Figure
2(a) shows choroidal hypofluorescence corresponding to a two-
ICGA disk-diameter-wide area of serous detachment (inferior margin
indicated by black arrows). Smaller areas of selective choroidal
• The application of ICGA to the study of CSC has expanded hypofluorescence near its upper border are marked using red
the knowledge of the disease26. arrows. During the angiographic mid-phase Figure 2(b), these
hypofluorescent areas demonstrate choroidal venous dilation and
• Common findings in patients with CSC are multi focal areas leakage at the locations in Figure 2(b), that correspond to the red
of hyperfluorescence in the early and midphases of the study, arrows in Figure 2(a).
which then fade in the late phase of the study.
OCT27,28,29,30,35
• Typically these areas of hyperfluorescence are found not only
in congruence with the leaking point seen with FA, but also in • OCT reveals many aspects of pathophysiology of CSC,
fundus areas that appear clinically and angiographically ranging from subretinal fluid, pigment epithelial detachments,
normal, and in normal fellow eyes of patients with CSC. & retinal atrophy following chronic disease (Figure 2 to10).

• These areas of early hyperfluorescence are believed to • OCT is especially helpful in identifying subtle, even subclinical,
represent diffuse choroidal hyperpermeability. neurosensory & macular detachments.

28 DOS Times - Vol. 15, No. 4, October 2009

Figure 2(a): ICG Early Phase Figure 2(b): ICG Mid Phase

Figure 3 : Fundus Autofluorescence image Figure 5: Image of Normal Fovea showing the Ultra
High resolution Spectral / Fourier Domain OCT.
Figure 4: Image of Fovea with the standard
Time Domain OCT • OCT is also helpful in identifying the dreaded complication
of Choroidal Neo Vascular membrane (CNVM) in CSC
www.dosonline.org (Figure 9).

OCT helps in evaluating the presence of shallow fluid in CSC as
also the volume of fluid that may be of prognostic value as well as
aid in patient education. It is especially helpful in identifying subtle,
even subclinical, neurosensory macular detachments. Central
serous chorioretinopathy is characterized by the presence of fluid
between the RPE and the neurosensory retina causing a
neurosensory detachment. Spaide,et al. correlated lipofuscinoid
deposition of material in CSC that might mimic vitelliform lesions
in pattern dystrophies. OCT shows accumulation of this material
on the outer surface of the retina in neurosensory detachments.

With the latest Spectral / Fourier Domain technology, the
interference from a range of depths is captured almost
instantaneously by taking a snapshot of the light’s spectral
composition. High-speed OCT systems using Spectral/Fourier
domain detection enable dense raster scan patterns of multiple

29

Figure 8: OCT showing a "Dome shaped" elevation
of the red line representing the RPE. This
corresponds to an area of retinal Pigment

Epithelial Detachment (PED) underlying the CSC

Figure 6: Images of Central Serous Choroidopathy
showing the comparison by Time Domain OCT vs.

Spectral / Fourier Domain OCT

Figure 9: OCT showing CSC with Choroidal Neo
Vascular membrane (CNVM)

Figure 7: OCT showing a typical case of retinal
detachment due to CSC

Microperimetry33

cross-sectional images for Three-Dimensional OCT (3D-OCT) Microperimetry-1 (MP1, Nidek technologies, Italy) is an
data sets. instrument for fundus-related perimetry. It captures fundus images
of the patient’s retina and at the same time projects light stimuli
Montero et al described Two patterns of OCT: - onto the retina. The light stimuli size have been correlated to
Goldmann stimuli sizes (Goldmann I-V) and the pattern are chosen
1. An optically empty vaulted area of different heights under by the operator and can therefore be adapted to different diseases
the neurosensory retina. Highly characteristic small bulges of the macula. The patient’s subjective response to each stimulus
protruding from the RPE, angiographically related to leaking (seen/not seen) is recorded (functional information) together with
spots. the retinal location of the stimulus (anatomical information)
(Figure 12).
2. An almost semicircular space under the RPE, with thinner
overlying retina. Retinal Microperimetry (MP1) allows an accurate analysis of the
central retinal function, combining a digital retinography, a
Other Tests computerized perimetry and a fixation assessment in one exam.
In combination with other retinal investigation devices, MP1 has
Multifocal Electroretinogram (mfERG) (Figure 11a, 11b) has been already helped us and will in the future help us to follow and to
used to identify focal regions of decreased retinal function, even in understand retinal diseases. It has also shown that, despite clinical
asymptomatic or clinically inactive eyes. Furthermore, resolution of CSC, there is lower retinal sensitivity in the macula
investigators, including Lai et al, are using mfERG as a means of even once visual acuity returned to 20/20. Fixation studies showed
assessing the efficacy and safety of new treatment modalities for stability of central fixation. Springer et al. investigated patients
CSC. During acute CSC, retinal dysfunction is reflected by reduction with Central Serous Choroidopathy (CSC). The MP1 enables
in mfERG response amplitudes and delay in implicit times. With quantification of functional defects in patients with CSCR.
the use of mfERG, it has also been demonstrated that the fellow
eye of patients with CSC may have abnormal mfERG responses. It Natural History of CSC
has been shown that mfERG abnormalities may persist even after
resolution of the subretinal fluid clinically. Thus, mfERG may • If left untreated - CSC heals spontaneously within 12 weeks
therefore have a useful role in providing an objective measure of with full recovery of VA ~ scar formation.
retinal function in research on the treatment for CSC.
• Recurrence in 1/2 to 1/3rd Pts is seen

30 DOS Times - Vol. 15, No. 4, October 2009

Duration Examination Detachment Stress, Treatment
Acute Hypercortisolism
Fine granular subretinal High bullous OCT Conservative, counseling;
deposits if duration more > 100 μ subretinal Common, recurrent if no resolution within 3
than a few weeks; fluid months of onset,
monofocal leakage consider focal
photocoagulation if
safe, otherwise PDT

Recurrent Paucifocal (1-5) Moderate 51-100 μ Common Photocoagulation if safe,
otherwise PDT

Chronic Multiple semi confluent Shallow, often < 50 μ Past, current, PDT
hypopigmented RPE inconclusive or none
lesions; confluent
subretinal material

Sequelae RPE depigmentation None Past, inconclusive None
without RPE atrophy or none

Neovascularization CNV plus CSC Sequelae; Variable mainly History of CSC, PDT &/or intravitreal

subretinal fibrosis around CNV associated RPE changes Anti-VEGF

• Recurrent CSC-2 or more episodes separated by >= 3 months.

• Chronic CSC.

• Sequelae.

• Neovascular CSC.

• The high spontaneous remission rate favours conservative
management.

• Lifestyle counselling & discontinuation of corticosteroids as
first line options.

Figure 10: OCT in CSC showing large RPE breach and • If detachment persists for more than 3 months,
retinal thickening from inspissated fluid photocoagulation or PDT should be considered.

• Systemic acetazolamide promotes the resorption of SRF.

• 3 or more recurrence seen in 10% pts • However, there is no evidence that treatment promotes
healing of the RPE lesion, long-term preservation of visual

• Recurrence seen mostly with in 1 yr of disease but may recur function, or a reduced rate of recurrence.

up to 10 yrs. Laser Photocoagulation

• Even a small single episode of CSC may be followed by chronic • Has been used for decades.
slowly progressive disturbances of RPE at post pole.

• Accelerates the resolution of the detachment.
• Small percentage may develop CNV, perifoveal RPE

atrophy or cystic macular degeneration with severe and • Also lowers the recurrence rate to about one fifth of what

irreversible loss of central vision. would be expected without active treatment.

• Larger PEDS may have – multiple recurrence, sub retinal • This beneficial effect of photocoagulation treatment can be

fibrin deposits, multi focal leaks, dependant neurosensory explained as follows: -

detachment and atrophic RPE tracts. • The coagulation beam destroys the cluster of diseased

Treatment pigment epithelium cells, thus stopping the secretion of
fluid beneath the neurosensory retina.

For treatment of the disease it is divided into 5 types: - • The resulting scar helps to transport fluid back into the

• Acute CSC. choriocapillaris.

www.dosonline.org 31

(a)
(b)

Figure 12: Fundus microperimetry of
the left eye with CSC

Technique

• Strategy is to apply laser energy so as to obtain a confluent
coagulation of moderate intensity covering the site of leakage
responsible for the foveal detachment.

• Spot size – 200μ.

• Exposure time – 0.2s.

• End point – bleaching without whitening of outer retina.

• When multiple leaks are present, leakiest one should be
treated first.

• Anatomic resolution of the macular detachment generally
occurs in about 2 weeks in uncomplicated cases.

Figure 11a: OCT demonstrating a pocket of sub-retinal Fluid • But it may require up to 6 weeks in long-standing detachments
beneath the fovea. Figure 11b: mfERG trace array and three- with turbid sub retinal fluid.
dimensional topography plot demonstrating the diminished
response at the central macula corresponding with the location • Complete visual recovery usually requires twice the amount
of time.
of the subretinal fluid of the above image (12a).
Complications

Indications • Worst is, inadvertent photocoagulation of the fovea.

• Persistence of serous detachment for more than 3 months. • Persistent scotoma after treatment (should be told to the

• Recurrences in eyes with visual deficit from previous episodes. patient before giving treatment).

• Secondary CNVM.
• Presence of permanent visual deficit from previous episodes

in fellow eye. • Progressive enlargement of the area of RPE atrophy.

• Development of chronic signs i.e, cystic changes in Photodynamic Therpy
neurosensory retina or widespread RPE abnormalities. Indications: -
• Juxtafoveal lesion.
• Occupational or other patient needs that require prompt • Subfoveal lesion.
restoration of vision or stereopsis. • Lack of a clearly defined leakage hot spot.

If leakage point is within 500 microns from the center of fovea, wait
for 6 months before treating.

32 DOS Times - Vol. 15, No. 4, October 2009

• Concern about the potential induction of CNV. 20. Haimovici R, Koh S, Gagnon DR, Lehrfeld T & Wellik S (2004): Risk factors
for central serous chorioretinopathy: a case–control study.
The use of half-dose verteporfin (3 mg/m2) or low fluence PDT Ophthalmology 111: 244–249. Haimovici R, Rumelt S & Melby J (2003):
(50% reduced light fluence) is done as a precaution against
permanent RPE or choriocapillaries damage.34 21. Endocrine abnormalities in patients with central serous chorioretinopathy.
Ophthalmology 110: 698–703.
Recently, Subthreshold diode laser has been tried in the treatment
of ICSC with point source leakage.36 22. Iwami S (1995): A new method to elicit pathological entoptic phenomenon
from the retina–stenopeic ûicker test. Nippon Ganka Gakkai Zasshi 99:
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2. Van Graefe A. Veber Central receidivirende retinitis. Albert Van Graefes
Arch Ophthalmol 1866; 12:211-215. 24. Eandi CM, Ober M, Iranmanesh R, Peiretti E & Yannuzzi LA (2005): Acute
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Digital indocyanine green videoangiography of central serous
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II Idiopathic central serous chorioretinopathy. Am J Ophthalmol 1967;
63:587-615. 27. Royce W. S. Chen et al. Speed and Resolution Improve in Newest OCT –
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6. Bennet G. Central serous retinopathy. Br J Ophthalmol 1995; 39:605-618.
28. Srinivasan V, Wojtkowski M, Witkin A, Duker J, et al. High-definition and
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29. Wojtkowski M, Srinivasan V, Fujimoto J, Ko T, et al. Three-dimensional
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9. Spaide RF, Goldbaum M, Wong DWK et al. Serous detachment of the 30. Puliafito C, Hee M, Lin C, Reichel E, et al. Imaging of macular diseases
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10. Ciardella AP, Borodoker N, Costa DLL et al. The expanding clinical 31. Timothy Y.Y. Lai, et al. The Clinical Applications of Multifocal
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11. Guyer DR, Yannuzi LA, Slakter JS et al. Digital indocyanine green 32. T.Vajaranant et al. Localized retinal dysfunction in central serous
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12. Ahnoux-Zabsonre A, Quaranta M & Mauget-Faysse M (2004): Prevalence 33. Pascal W. Hasler Microperimetry - a method which combines Perimetry
de l’Helicobacter pylori dans la chorioretinopathie sereuse centrale et and macular topography - Oftalmolog December 2007.
l’epitheliopathie retinienne diffuse. J Fr ophtalmol 27: 1129–1133.
34. Lai TY, Chan WM, Li H, Lai RY, Liu DT & Lam DS (2006): Safety enhanced
13. Cotticelli L, Borrelli M, D’Alessio AC et al. (2006): Central serous photodynamic therapy with half dose verteporûn for chronic central serous
chorioretinopathy and Helicobacter pylori. Eur J Ophthalmol 16: 274– chorioretinopathy: a short term pilot study. Br J Ophthalmol 90: 869–874.
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F & Megraud F (2002): Ro ˆle de l’Helicobacter pylori dans la choriore Ophthalmol 2005 89: 562-564.
´tinopathie se ´reuse centrale et l’e ´ pithe ´ liiopathie re ´ tinienne diffuse.
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37. Matsumoto H, Taku S, Kishi S. Outer Nuclear Layer Thickness at the Fovea
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Central serous chorioretinopathy associated with inhaled or intranasal
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www.dosonline.org 33

Pentacam: A Step Forward in Anterior Cornea
Segment Diagnostics

Amruta Padhye DNB, FICO, Sujatha Mohan DO, Mohan Rajan DO, DNB, FMRF

Recent advances in refractive surgery have led to rapid The key advantages of the rotating imaging process are the precise
developments in corneal imaging techniques. Corneal measurement of the central cornea, the correction of eye
topography, keratometry and pachymetry are vital parameters to movements, the easy fixation for the patients and the extremely
be evaluated in patients undergoing refractive surgery. The gold short examination time.
standard until recently was placido disc based topography. The
Pentacam has emerged as the latest weapon in the refractive Principle
surgeon’s armamentarium for corneal assessment (Figure 1).
The Pentacam obtains images of the anterior segment by a rotating
The Pentacam is based on a rotating Scheimpflug camera principle Scheimpflug camera which is a digital CCD (Charged coupled
(Figure 2) which captures images of the anterior segment of the device) camera with synchronous pixel sampling. The light source
eye. This Scheimpflug technique was first invented by Theodor consists of UV-free blue LED's (wavelength 475 nm). This rotating
Scheimpflug1 in aerial photography for surveying the land from process supplies pictures in three dimensions (Figure 3). The
air. Images of the earth taken from the satellite and images of the software utilizes a ray tracing algorithm to construct and calculate
cornea have one thing in common: both the objects to be the anterior segment. The device has two cameras, one on the
photographed are curved and both need to be depicted without centre for controlling fixation and one mounted on a rotating
distortions1. The earlier modes of corneal topography achieved wheel for capturing slit images2 thus allows the center of the cornea
this with the disadvantage of compromising the central 1-2 mm of to be measured precisely.
the cornea, which is indeed very vital for many applications, as the
camera would be placed in the centre, thus merely calculating the Pentacam takes 50 meridional sections through the center of the
central area rather than accurately measuring it. cornea. This approach allows the system to realign the central
thinnest point of each section before it reconstructs the corneal
The use of Scheimpflug principle has helped in providing sharp image, thus eliminating any eye movement that occurs during the
and crisp images that include information from the anterior examination.
corneal surface to the posterior crystalline lens capsule.
The Pentacam is available in three different models:

• Pentacam BASIC – the individual model

• Pentacam CLASSIC – the versatile model

• Pentacam HR – the professional model

Figure 1: The Pentacam Figure 2: Scheimpflug's principle

Rajan Eye Care Pvt. Ltd Hospital 37
Vidyodaya 2nd Cross Street, T Nagar, Chennai

www.dosonline.org

Figure3: During reconstruction of the image, Pentacam • Corneal thickness is calculated from the top of the epithelium
maintains the central point of each meridian to the anterior surface of the endothelium, excluding the tear
film3. It is displayed as a color image over its entire area from
limbus to limbus (Figure 5).

• The software allows for IOP modification taking into
consideration the corneal thickness (Figure 6). This feature is
of immense importance for obtaining IOP in post-refractive
surgery patients as well as ocular hypertension and glaucoma
screening.

• Important parameters like thickness in the center of the pupil,
apical corneal thickness and the thinnest location are provided.
The distance and position of the thinnest point relative to the
apex of the cornea are also available which are useful for
early detection of Keratoconus4,5

• Anterior chamber analysis includes a calculation of the
chamber angle, chamber volume and chamber height and a
manual measuring function at any location in the anterior
chamber of the eye6.

Comparative maps

2 maps comparison

This function allows an easy and comfortable evaluation in terms
of mapping and numerical analysis of the anterior segment

Figure 4: Refractive map showing 4 map display Figure 5: Corneal Pachymetry display

Software Highlights Figure 6: Pachymetry modified IOP
DOS Times - Vol. 15, No. 4, October 2009
Color coded Topographic maps

The relevant numerical data are represented on the left side; the
color-coded maps are depicted on the right side in the various
default settings. The map shown (Figure 4) below is the refractive
map, most useful to all the refractive surgeons. The upper left
map shows the anterior sagittal curvature which gives a clear
picture of the associated astigmatism and the left lower gives the
differential corneal pachymetry. The maps on the right give a true
elevation data both on the anterior and posterior corneal surface.

Pachymetry analysis Map

The Pentacam is the only instrument that measures and analyses
the center of the cornea precisely. This offers a significant advantage
in accurate corneal topography measurements prior to refractive
surgery.

38

Figure 8: Four map comparison display

Figure 7: Two map comparison model

progression. Especially for example - pre- and post op control of Figure 9: Keratoconus screening software
any corneal refractive surgery, YAG Laser Iridectomy, ring and
INTACS implantation, it provides an excellent and helpful
representation (Figure 7).

4 maps comparison

The 4 maps comparison menu offers an excellent long term follow
up representation of the anterior eye segment progression in terms
of mapping and numerical analysis, especially post collagen cross-
linking procedures (Figure 8).

Keratoconus (KK) screening

Keratoconus screening requires the use of topography systems
that measure elevation data as their elemental unit of measurement
and Pentacam is the only eye screening system that does not rely
on Placido-based technology but allows direct measurement of
elevation data (Figure 9).

There is an inbuilt Keratoconus screening software which when Figure 10: Corneal Wavefront Analysis
applied gives the grading as to whether a certain cornea is normal
or abnormal (KK-1, KK-2, KK-3, KK-4).Besides this classification,
it may also attribute KK possible in case of suspicious picture.

Corneal wavefront analysis

The anterior and posterior corneal surface is described separately New Contact lens fitting software
by Zernike polynomials based on the measured elevation data
(Figure 10). To make the OCULUS Pentacam/PentacamHR (High resolution)
also commendable for opticians and optometrists, OCULUS
Together the corneal wavefront analysis and keratoconus detection introduced the new Contact Lens fitting software for the Pentacam/
improve the pre-operative screening for patients who are PentacamHR (Figure 11).
interested in refractive surgery as well as the post-operative
progression control. Hence these are 2 indispensable tools for It adds the following features:
refractive surgery in order to increase patients safety and
satisfaction. • Pre-programmed recommendations for rigid and soft contact
lenses.

www.dosonline.org 39

Diagnostic criteria for detecting Forme fruste based on magnitude
of elevation maps put forth by Michel W. Belin7,8 is as follows:

Set the system to color extension and all display at 9.0 mm central
corneal zone.

• Normal values for anterior elevation are differences less than
+12 μm

• Between +12 and +15μm are suspicious

• Greater than +15 μm indicate Keratoconus.

• Normal values for posterior elevation are approximately 5
μm higher than those for anterior elevation.

Figure 11: Contact Lens fitting software Holladay also has proposed that when the 'hot spot' on the Anterior
sagittal map, Relative Pachymetry Map and Back Elevation Map
are all at the same point, the diagnosis of Forme Fruste
Keratoconus is confirmed.9

AC depth for Phakic IOL implantation

• Real fluoroscein image simulation on the cornea For the correction of refractive errors phakic IOL implantation
has gained increasing popularity. The 3D Chamber Analyzer in
• Automatic power calculation for contact lens the software is helpful for surgeons implanting phakic IOLs during
the pre-op assessment (Figure 12).
• Unlimited open database for Contact Lens geometries
The Pentacam analyses the complete anterior eye segment and
• Customized contact lenses can be added creates a mathematical model. Based on these data the
preoperative simulation of phakic IOL fitting is realized.
• Four quadrant contact lenses with progressive eccentricity
can be added as well It displays the internal anterior chamber depth at various points
(from posterior corneal endothelium to the anterior lens surface).
Applications of Pentacam
Phakic-IOL Fitting Simulation Software
Pre-refractive surgery screening
The phakic-IOL simulation software can be upgraded to each
Performing refractive surgery on healthy eyes demands high Pentacam HR system in the field.
standards in precise patient selection and preoperative diagnostic
examinations. One of the keys for successful refractive surgery is
to be able to identify with fair accuracy the patients with ectasia
and forme fruste keratoconus.

The refractive map in the Pentacam (Figure 4) can be set to default
settings to display 1) the differential corneal pachymetry, 2) Anterior
sagittal topographic map and the 3) Anterior elevation map and 4)
Posterior elevation maps. Step-wise approach can be useful;

• Locate the thinnest spot on pachymetry map with regards to
its X-Y co-ordinates to know whether the map is well centered
in order to get an idea of the data's validity.

• Note the value of the thinnest spot on the cornea.

• Evaluate the corneal curvature (sagittal map): Ideally, the
curvature map should be symmetric in both eyes.

• Elevation map should have well centered anterior and
posterior apices with minimal elevation above the best-fit
sphere (BFS), thus depicting the prolate shape of normal
cornea.

• Note the magnitude of the elevation of the anterior and Figure 12: AC depth display
posterior apices above the best-fit sphere (BFS) .

• Also, the pachymetric profile should be centered i.e. thinnest
in the centre and gradual thickening in the periphery.

40 DOS Times - Vol. 15, No. 4, October 2009

The pre-programmed database contains myopic and hyperopic Figure 16: Scheimpflug images
as well as spheric and toric phakic IOL. Based on patients refraction, -various lens grading
the refractive power of the phakic IOL is calculated automatically

The individual fitting position of the phakic IOL in the anterior
chamber is automatically simulated (Figure 13) which is based on
the data obtained from the distances of the peripheral implant
and the corneal endothelium (shortest distance between the
implant and the endothelium) and the distance from the implant
to the crystalline lens. It effectively and reliably illustrates the
location of the phakic IOL positioning in relation to crystalline lens
as well as cornea and the software can extrapolate this position for
several decades into the future.10

The distance from the anterior surface of the crystalline lens to
the corneal endothelium is very crucial when contemplating the
insertion of a phakic IOL (internal AC depth). The Pentacam can
also interpret the angle of the anterior chamber and give an idea

Figure 13: Three-dimension image showing future of how open it is and whether there is any significant anterior
location of phakic-IOL in the anterior chamber. vaulting of the iris and the lens11.

The minimum clearances are calculated in 3D and displayed
separately for a quick evaluation and shown in each single
Scheimpflug image (Figure 14).

• The phakic-IOL can be centered on the pupil, to the line of
sight or on the iris profile the phakic IOL can be moved, tilted,
shifted manually to simulate different positions.

• The system also offers the possibility to manually measure
the diameter of the anterior chamber or the distance between
iris and posterior surface of the cornea for a more comfortable
pre-operation planning (Figure 15).

Lens densitometry

Figure 14: The horizontal Scheimpflug image shows a The density (light transmittance) of the crystalline lens is visible by
minimum clearance between optic edge and illumination with blue light. Scheimpflug images allow for an
automatic and objective quantification of the lens density12. It also
ephothelium of 1010μm but the true minimum has a density graph to the right of the image, which allows the
clearance calculated in 3D between the pIOL optic physician to quantify visual disturbances in the media (Figure 16).

edge and the endothelium is 1.00mm only • The grading of lens density through Scheimpflug images has
been found to correlate well with the LOCS III grading system
Figure 15: Manual measurement of for cataracts.
anterior chamber
• It is also excellent for identifying intra-lenticular foreign bodies,
anterior and posterior sub-capsular cataracts.

• Crystalline lens opacification can be quantitatively imaged
and analyzed using the Pentacam. The densitometry software
provides an objective record of a cataract's grade prior to
surgery and serves as an excellent patient counseling tool.

• Another interesting application is in diagnosing Capsular Bag
Distension Syndrome (CBDS)2 Early stages of CBDS are often
missed on a slit lamp examination. It appears to be an excellent
tool for demonstrating Elschnig pearls, posterior capsule
opacification and late cases of CBD (Figure 17).

Improved IOL calculations

The big step forward making IOL calculations much easier are the
so called Equivalent Keratometer readings, (EKRs).

www.dosonline.org 41

Figure 17: Scheimpflug images showing it can accurately predict a patient's net corneal power which can
Capsular Bag Distention Syndrome help to predict an implant's power.

Figure 18: True Corneal Net power display The standard keratometers were found to be unreliable to calculate
(left upper corner) the proper IOL power in such patients as they calculated the
refractive power using an approximate ratio between back/front
corneal radii (approximately 82.5%), which leads to an overall
corneal refractive index of 1.33. Because refractive surgery alters
this relationship, these keratometric measurements cannot be
acceptable to be plugged into standard IOL formulas without
performing additional recalculations13

However, in the "Holladay Report" incorporated in the Pentacam
software the ratio between back and front power of the cornea is
calculated for the current examination as well as the "Equivalent
K-Readings" of the cornea (Figure 19).

These "Equivalent K-Readings" can be implanted into the IOL
calculation formulas to get a more precise IOL power calculated
for all patients, including those with abnormal corneas.

IOL Power Calculation

IOL power calculation for post-refractive correction cataract
patients was a challenge especially if no pre-operative data were
available.

The Holladay IOL Consultant Software and Holladay II formula
(both by Holladay Consulting, Inc.), was the first formula to
incorporate a double-K method to remove the artifact of an
iatrogenically changed central corneal power.14

Also the recently introduced BESSt (Borasio Edmondo Smith and
Stevens) formula uses the Pentacam derived anterior and posterior
corneal radii and central pachymetry data to calculate TRUE
Corneal POWER (Figure 18) based on Gaussian optics formula
without relying on the pre-refractive surgery historic information15.

IOL power calculation for the post-refractive surgery patient is a Figure 19: EKR calculation: In the upper left-hand
2-step process. corner is the patient's demographic information. The
top center box shows the equivalent K readings that
Estimation of the true central corneal power. may be used for IOL calculations.In the upper right-
hand corner is where the program calculates what the
Eliminate the artifact, corneal power (of a very flat or very steep
central corneal power from the effective lens position) part of the Ks would have been before refractive surgery
IOL power calculation. This artifact can lead standard third-
generation, (two variable formulas) to incorrectly estimate the DOS Times - Vol. 15, No. 4, October 2009
effective lens position when carrying out the IOL power calculation.
This is because several popular two-variable formulas, such as
SRK/T, tie the effective lens position to the central corneal power

Problems faced which were overcome by the Pentacam

The problem with using standard keratometers is that they are
completely blind to the central cornea, measuring instead an
intermediate zone and extrapolating a central value. A placido
based topographer, also has a blind spot in the center. For patients
who have undergone prior myopic refractive procedures, this
problem may lead to a significant overestimation of the central
corneal power.13

The Pentacam, on the other hand measures the central cornea
and the anterior and posterior corneal surface very precisely. Thus,

42

Figure 21: Pentacam HR: Flap delineation
in LASIK patients

Figure 20: Automatic Release

Advantages of the Pentacam Figure 22: Pentacam HR: Residual Bed
post LASIK

Imaging methodology: The Pentacam is the only Scheimpflug device • The learning curve is also very short and the machine is
that rotates around a common axis and allows the user to toggle friendly for both the patient and the operator.
down through each individual image and to see if there is a blinking
eyelid or eye movement that degrades the image's quality for that • The inter-operator reliability is higher using the automatic
meridian. release mode (Figure 20).

Advantage over placido-disk based topography: The Pentacam Disadvantages
being a tomographer, differs from the Placido-disc topography, as
it goes beyond topography and pachymetry and enables a 3- The Pentacam's new densitometry software is not without
dimensional corneal reconstruction, which evaluates its anterior limitations. A poorly dilated pupil interferes with the device's
and posterior curvatures and creates a pachymetric map. sampling ability, and so eyes with pseudo-exfoliation, trauma,
and intraoperative floppy iris syndrome, for example, are
Advantage over Orbscan: The Pentacam Comprehensive Eye problematic. Also, white cataracts block the system's ability to
Scanner differs fundamentally from the Orbscan (Bausch & Lomb, sample the central nucleus.
Rochester, NY) by the way in which it takes image slices of the
cornea. The Orbscan takes vertical image slices that are separated Newer Advances
from one another and have no common point. Thus, the Orbscan
cannot re-register for any eye movement that occurs while it is The new HR Pentacam has an improved optic design and a high
capturing the images. The Pentacam maintains the central point resolution 1.45 Mega Pixel Camera. Primary advantages are:
(the thinnest point) of each meridian. Thus, during the examination,
the software can re-register these central points and eliminate the • Corneal imaging via a fine scan produced by 100 images in
eye movement. This single feature makes the Pentacam's less than 2 seconds provides for improved accuracy.
measurements 10 times more accurate.
• An active, shifting fixation target to allow patients with high
Newer Software ametropia an easy fixation.

• The New Holladay Software facilitates for an improved and • Crisper and sharper Scheimpflug pictures allowing excellent

less tedious IOL power calculation in post refractive patients. IOL and phakic IOL implant imaging. The phakic-IOL

• The Phakic IOL simulation software is extremely useful to simulation software can be upgraded to each Pentacam HR
plan phakic IOL implantations by imaging and calculating the system in the field.

dimensions of the anterior chamber for adequate space • More precise presentation of the corneal layers, thus helping

• The Pentacam's densitometry software simplifies cataract in evaluating the flap thickness (Figure 21), residual corneal
grading into a single, test that provides a reliable, reproducible bed (Figure 22), the positioning of INTACS (Figure 23).

way of sampling the volume and density of the nuclear cataract Concluding, the Pentacam's unique imaging system plays a vital
and objectively classifying it into different grades. Having this role in accurately assessing both the anterior and posterior corneal
pre-operative knowledge, allows surgeons to pre-program surfaces and thus offers the state of the art in topographic screening.
their phaco-emulsification systems to handle the specific The Pentacam analysis of the anterior segment allows one to make
density of cataract efficiently. an accurate surgical decision and helps in executing the best surgical

• With the option of new Contact Lens fitting software, the treatment plan for patients. Its ease of use, rapid scanning ability,

Pentacam HR has become, the most versatile instrument for reproducibility, high index of reliability and the ability to map and

the advanced optician/optometrist. measure the anterior segment structures is currently unsurpassed.

www.dosonline.org 43

4. Lackner B, Schmidinger G, Skorpik C. Validity and repeatability of
anterior chamber depth measurements with pentacam and orbscan.
Optom Vis Sci 2005;82:858-61.

5. O'Donnell C, Maldonado-Codina C. Agreement and repeatability
of central thickness measurement in normal corneas using ultrasound
pachymetry and the OCULUS Pentacam. Cornea 2005; 24:920-4.

6. Rabsilber TM, Khoramnia R, Auffarth GU. Anterior chamber
measurements using Pentacam rotating Scheimpflug camera. J
Cataract Refract Surg. 2006;32:456-459

7. Micheal Belin, Keratoconus / Ectasia Detection with the Oculus
Pentacam; Vol 35, Number 6: 5-12.

8. Carlos Verges, Jorge Cazal, Applications of Pentacam in Anterior
Segment Analysis,Highlights of Ophthalmology;35,3:11-15

9. Jack T Holladay, Detecting Forme frustae Keratoconus with the
Pentacam, J Cataract Refractive Surgery supplement ,Feb 2008;11-
12

Figure 23: Pentacam HR: Corneal INTACS 10. Mana Tehrani, Improving phakic IOL patient selection with the
Pentacam, In: Pentacam opens eyes to new diagnostic possibilities,
EUROTIMES supplement, Feb 2007; XXIV Congress of the ESCRS
London, Sept 2006: 2-3.

11. Jason E Stahl, High-Tech measurements for Phakic IOLs, Review of
Ophthalmology, Vol. No: 12:10,Issue: 10/1/2005.

As Ophthalmology evolves into an era where imaging is of prime 12. Tkachov SI, Lautenschläger C, Ehrich D, Struck HG. Changes in
importance, the Pentacam has emerged as an indispensible the lens epithelium with respect to cataractogenesis-light microscopic
diagnostic tool, for the modern anterior segment surgeons. and Scheimpflug densitometric analysis of the cataractous and the
clear lens of diabetics and non-diabetics. Graefes Arch Clin Exp
References Ophthalmol. 2006; 244:596-602.

1. Toblas H. Neuhann, Pentacam system's Overview:Understanding 13. Warren E. Hill, IOL Power calculation after Kerato-refractive surgery,
its benefits,Highlights of Ophthalmology,2007,Vol 35,(1);1-3 In: Pentacam offering a clearer view; J Cataract and Refractive
Surgery Supplement,2007 Symposia; Feb 2008;13-15.
2. Satinder Pal S. Grewal, Evaluation of Anterior Segment pathologies
using Pentacam, Highlights of Ophthalmology,2008,Vol 36 (1);17- 14. Jack Holladay, Holladay report on the Pentacam: In Newer Advances
20. and Technology in Pentacam, Oculus supplement on Pentacam, by
Highlights of Ophthalmology, 2008; 10-15.
3. Barkana Y, Gerber Y, Elbaz U, et al. Central corneal thickness
measurement with the Pentacam Scheimpflug system, optical low- 15. Borasio E, Stevens J , Smith GT (2006),Estimation of true corneal
coherence reflectometry pachymeter, and ultrasound pachymetry, J power after kerato-refractive surgery in eyes requiring cataract
Cataract Refract Surg. 2005; 31(9)1729-1735. surgery, BESSt formula, J. Cataract and Refractive
Surgery,32(12),2004;1-14.

First Author
Amruta Padhye DNB, FICO

Kindly send New E-mail address for DOS Correspondence
Email: [email protected]

44 DOS Times - Vol. 15, No. 4, October 2009

Pre-operative Evaluation for LASIK Refractive Surgery

Ranjan Dutta MD, Dariel Mathur DO, MS, FMRF, Yamini Kaushal BSc (H)

LASIK (Laser in-situ Keratomilieusis) is currently the most glaucoma suspect, or have ocular hypertension or those who have
popular refractive surgical procedure. Advances in LASIK a history of uveitis.
technology have made it a safer procedure over recent years and
provide patients with choices that can reduce the risk of post- Systemic problems: One should make a note of diabetes mellitus,
operative complications and provide more precise results. Given hypertension, cardiac ailments, asthma, thyroid disorder,
the popularity of LASIK, there maybe a tendency for patients to depression, and use of systemic steroids. A special effort should
trivialize the procedure. It is therefore vital for the refractive surgeon be made to rule out collagen vascular disorders / autoimmune
to impress upon prospective surgical patients regarding the disorders (Systemic Lupus Erythematosus, Rheumatoid Arthritis,
inherent risks, though rare. A thorough screening is mandatory to Polyarteritis Nodosa, Sjögren’s Syndrome, Pemphigus,
identify risk factors so as to prevent complications, especially with Scleroderma, and Sarcoidosis), and immunodeficiency states (e.g.,
regard to iatrgenic keratectasia which may occur weeks to years HIV). Elicit symptoms such as joint pains, muscle pains, skin rashes,
after the procedure. hair loss, and dryness of mouth, nose and eyes. These may prevent
proper healing after a refractive procedure and are considered
Preoperative evaluation for refractive surgery should follow a relative contraindications. One should also enquire regarding
systematic approach that includes a comprehensive history keloid formation and excessive scarring of wounds. PRK or LASEK
followed by a complete ophthalmologic examination. The aim of is to be avoided in such cases; LASIK may be safer option in such
preoperative evaluation, besides collecting specific refractive data patients given the minimal wound healing response.2
for the actual treatment, is to answer three broad questions in
addition to generating: 1) Is it possible to safely perform refractive Pregnancy/Lactation/Oral Contraceptives: These conditions create
surgery in the patient; 2) What is the risk of possible complications, hormonal imbalances and changes in the refractive status.
given the patient specifics; and 3) Is it possible to meet the Moreover, they may lead to unpredictable refractive outcomes
expectations that the patient has from the surgery? and are therefore a contraindication for excimer laser vision
correction.
History
Medication: Certain medications such as Isotretinoin for acne or
Age: Although the lower age limit according to some is 18 years, it Amiodarone hydrochloride are contraindications for LASIK.
is preferable to wait till 21 years to ensure a stable refraction. One Medications that suppress the immune system can make LASIK
should ascertain that there has been no significant change in extremely risky. In addition, some medications can cause dry eye
refractive error in the past 6 months to one year. syndrome, and dry eye symptoms must be controlled before
LASIK is performed.
Contact lenses: Patients are advised to discontinue wearing contact
lenses at least two weeks prior to the preoperative evaluation. Occupation: Patients engaged in sports in which blows to the face
Information regarding the type of lenses used (Soft or Rigid Gas and eyes are a common occurrence (boxing, wrestling or martial
Permeable) is important. Those wearing RGP lenses may be arts), or in occupations that have a greater likelihood of producing
required to stay off contacts for a much longer time to rule out trauma or injuries (armed forces or police) may have refractive
corneal warpage. surgery but should be offered PRK, LASEK or epi-LASIK as
alternatives to LASIK. Since refractive surgery may cause loss of
Ocular problems: Careful history should be taken with regard to best corrected visual acuity, loss in contrast sensitivity or higher
dry eyes, strabismus, amblyopia, eye injury, eye infections (corneal order aberrations, patients should check with their prospective
infections), glaucoma, uveitis, steroid response, previous ocular employers about the qualifying refractive criteria.3
surgery (RD surgery, IOL surgery, glaucoma surgery, operated
RK, PRK), family history of glaucoma, keratoconus and retinal Ocular Examination
detachment. If the patient has a history of prior refractive surgeries,
particularly radial or astigmatic keratotomy, then additional Visual Acuity & Refraction: This includes recording uncorrected
refractive procedures (PRK or LASIK) are associated with Snellen visual acuity, visual acuity with present glasses, dry manifest
unpredictable refractive outcomes and greater potential refraction and wet manifest refraction (after cycloplegia). Accurate
complications. manifest refraction is performed using techniques to prevent
accommodation (fogging technique). The strongest plus lens
Refractive surgery is contraindicated in patients with keratoconus, (convex) in hyperopes and the weakest minus lens (concave) in
and in those with history of Herpes simplex or Herpes zoster myopes that allows best visual acuity is determined. Cross cylinder
ophthalmicus, as reactivation of Herpes virus has been reported technique is used to determine the strongest cylinder and the axis
in the postoperative period.1 Relative contraindication for refractive that allows best visual acuity. Cycloplegic refraction is essential
surgery includes patients who have glaucoma, patients who are important to uncover pseudomyopia due to spasm of
accommodation and latent hyperopia. Tests to ascertain the
Shroff Eye Centre dominant eye in presbyopic patients should also be done.
A-9, Kailash Colony, New Delhi
Accurate determination of the refractive error is one of the
cornerstones upon which the refractive outcome of LASIK is based.

www.dosonline.org 49

Depending upon the amount of refractive error it is possible to
plan the type of refractive treatment (standard or wavefront-
guided). The usually accepted guidelines of correction are: myopia
up to –12 dioptres of sphere, hypermetropia up to +5 dioptres of
sphere, and astigmatism up to 4 dioptres of cylinder.

Contrast Sensitivity & Glare Testing: These tests are not routinely
done. Some employers require contrast sensitivity testing and
glare disability measurement in addition to determining
uncorrected Snellen visual acuity after the refractive surgery
procedure.

Aberrometry: Although this is done for cases undergoing Figure 1: The Oculus Pentacam (Optikgeräte GmbH) is a
customized (wavefront-guided) LASIK, it is a good practice to rotary Scheimpflug camera device that captures radial
perform this in patients undergoing standard treatment as well,
as it helps refine the refractive error. When aberrometry is done corneal slices centered about the apex. It provides anterior
with the VISX WaveScan Aberrometer, the refraction calculated and posterior corneal topographical analysis, point to point
for a 4-mm pupil correlates well with the manifest refraction
especially with regard to the cylinder axis and magnitude. corneal thickness measurements, anterior chamber depth
analysis and crystalline lens densitometry.
Intraocular Pressure (IOP): Tonometry is necessary to exclude
undiagnosed ocular hypertension or glaucoma and to establish a The scotopic pupil size should be measured with an infra-red
pre-operative IOP level. device such as the Colvard pupillometer at a room illumination of
room light level of approximately 4 cd/m2 or darker. The ablation
Slit-lamp examination: Examination of the lids and adnexa, and zone is therefore planned according to scotopic diameter. One
tear film evaluation should not be omitted. Specifically, the presence must keep in mind that the ablation zone consists of the central
of blepharitis should be noted and treated if present prior to functional optical zone which is 25% less than total ablation
surgery to decrease the risks of infection and interface diameter, and a surrounding peripheral blend zone. It is the
inflammation following surgery. functional optical zone which should be kept larger than the
scoptopic pupil size.
The presence of superficial punctuate keratitis (SPK) may be due
to dry eyes. A Schirmer test should be performed; wetting of less Pachymetry: The most common method is ultrasonic pachymetry
than 5 mm in 5 minutes is consistent with severe dry eye disease. which is an efficient and accurate way to measure corneal thickness;
Since after the refractive surgery the dry eye disease will most however, the probe must touch the corneal surface requiring
likely worsen, the patient should be counseled about this possibility. topical anesthesia. Its accuracy is dependent on the perpendicularity
Punctual plugs may be placed prior to or immediately after surgery. of the probe’s application to the cornea and reproducibility relies
on precise probe placement on the corneal center. It may be
The cornea should be examined for clarity, scars and difficult to accurately locate the same point of measurement in
vascularization. Habitual contact lens wearers with peripheral serial examinations. Moreover the central point need not
vascularization may have bleeding after flap creation. The presence necessarily be the thinnest point of the cornea.
of clinical signs of keratoconus (corneal thinning, Fleisher’s ring
and Vogt’s striae) should be noted. As mentioned earlier, refractive Over the past few years, newer non-contact devices have been
surgery is not performed in patients who have keratoconus developed to measure corneal thickness.5 The Orbscan II corneal
topography system (Bausch & Lomb) is an optical scanning-slit
The crystalline lens should be examined under dilation for presence instrument that provides topographic analysis and pachymetric
of cataract. This should be kept in mind as a significant number of measurements of the cornea. The SP-3000P specular microscope
patients nowadays are opting for refractive surgery in the (Topcon Corp.) is a noncontact optical instrument that provides
presbyopic age group. pachymetric measurements and specular microscopy
simultaneously. The central corneal thickness measurements are
Fundus examination: Posterior segment examination through higher with Orbscan than with ultrasonic pachymetry. This disparity
dilated pupils by indirect ophthalmoscopy is mandatory in all between instruments can result from their distinct methodologies.
patients undergoing LASIK. The peripheral retina should be The noncontact Orbscan system measures the hydrated mucous
screened and prophylactic laser treatment should be performed component of the tear film over the cornea; contact ultrasonic
in all cases where indicated. LASIK should be then re-scheduled pachymetry does not. More recently the Oculus Pentacam
2-3 weeks after such treatment. (Optikgeräte GmbH) (Figure 1) is proving to be a promising device
in this regard. It is a rotary Scheimpflug device which can provide
Pupil size: Patients with large pupils are not good candidates for anterior and posterior corneal topographical analysis, point to
LASIK. Patients with pupil diameters larger than the laser optical
zone or functional optical zone (not including the blend zone) may
suffer from permanent, debilitating visual aberrations such as
starbursts, halos, multiples images and loss of contrast sensitivity
at night after LASIK.4 For a given pupil size, the effects are more
disabling for higher amounts of myopic correction.

50 DOS Times - Vol. 15, No. 4, October 2009

Figure 2: Four-map display (Oculus Pentacam) showing Figure 3: Same patient
tangential map (top left), corneal pachymetry (top right), (as in Figure 1) showing normal
front elevation (bottom left), and back elevation (bottom
right) of the left eye. This patient had a significant posterior indices (circle) based on
corneal elevation (arrow) and was advised against LASIK anterior topographical analysis

point corneal thickness measurements, anterior chamber depth incorporate mathematical indices to detect subtle keratoconus
analysis and crystalline lens densitometry. While measuring topographically. If the Inferior-Superior (I-S) value is more than
corneal thickness, it does not consider the tear film and provides 1.4, keratoconus is suspected and should be ruled out. In order to
measurements comparable to ultrasonic pachymetry. exclude the possibility that the inferior steepening may be due to
contact lens warpage, a repeat topography should be performed
The safety goal for LASIK is to leave a central residual stromal bed after 2 additional weeks of discontinued contact lens wear. Contact
beneath the microkeratome flap that will allow corneal stability lens warpage induced steepening will reduce on subsequent
and prevent bulging or ectasia since the flap itself does not topography examinations whereas keratoconus steepening will
contribute to stability of cornea. The minimum safe bed thickness remain unchanged or increase.
is thought to be at least 250 microns, with many surgeons
recommending leaving 275 or 300 microns. The thinnest corneal Traditional corneal topography systems (Placido-based) only
pachymetry minus both the residual stromal bed, and the flap provide information about the anterior corneal surface. However,
thickness (120 to 140 microns, depending upon the since forme fruste keratoconus often shows changes only on the
microkeratome), will give an estimate of the amount of corneal posterior corneal surface, the standard of care should include
tissue available for ablation. If the cornea is thin (less than 500 evaluation of both corneal surfaces, by a slit-scanning or elevation-
microns), the tissue available may not be sufficient for the given based system, such as the Orbscan II or Oculus Pentacam. Patients
refractive error. PRK, LASEK or Epi-LASIK may then be preferable with keratoconus and forme fruste keratoconus have higher
to LASIK. anterior and posterior elevation on Orbscan II topography and is
a helpful tool for identifying patients who are potentially at high
Corneal Topography: Computerized corneal topography risk for developing ectasia after LASIK. Similarly, the Oculus
examination is essential to detect irregular astigmatism, whether Pentacam and the Oculus Pentacam HR are extremely useful in
from contact lens warpage or other causes, which, if significant, is distinguishing between normal and abnormal corneal shapes,
a contraindication to LASIK. It also provides the Sim K (flat and especially when analyzing the posterior surface. As mentioned
steep meridians, and average) which is used to select the diameter previously, the Pentacam rotary Scheimpflug camera captures
of the microkeratome flap cut. Larger flaps (9.5 mm) are planned radial corneal slices centered about the apex. The immense density
for flatter corneas (41 D or less) to avoid free caps, and smaller of data in the central region provides accurate analysis of this
flaps (8.5 mm) for steeper corneas (48 D or more). Thicker flaps region. Special algorithms have been designed such as the Belin-
(140 microns or more) are chosen for steeper corneas to avoid Ambrosio Display and Holladay Report to identify and quantify
flap buttonholes. the amount of posterior elevation present in a given case.8 These
are compared to normative data and guide the refractive surgeon
Corneal topography is used to screen for keratoconus or in deciding about the safety of a contemplated refractive procedure
asymmetrical steepening, which may be associated with (See Figures 2 to 5 for clinical examples).
unpredictable refractive outcomes and progressive ectasia after
LASIK.6,7 Although moderate to severe keratoconus is difficult to Counseling
misdiagnose, it is the mild and forme fruste keratoconus cases
which need to be detected. Inferior steepening, and asymmetric Patient expectation: It should be emphasized that the goal of
bowtie pattern with skewing of the axes of the hemi-meridians refractive surgery is to reduce the dependence on glasses and
could suggest presence of keratoconus. All topography systems contact lenses in a safe and effective way and not elimination of

www.dosonline.org 51

Figure 4: Same patient (as in Figure 1) depicting an Figure 5: Four-map display (Oculus Pentacam)
abnormal shape of the posterior corneal surface as showing normal scans of a patient undergoing LASIK.
analyzed by the Belin-Ambrosio Enhanced Ectasia Display
Note the symmetrical bow-tie patterns on the
programme of the Oculus Pentacam tangential, front elevation and back elevation maps

spectacles entirely. Some occupations require a certain level of Figure 6: Same patient (as in Figure 5) depicting normal
uncorrected visual acuity whereas others accept a residual spectacle shapes of the anterior and posterior corneal surfaces as
power less than a defined value. Although majority of patients can analyzed by the Belin-Ambrosio Enhanced Ectasia Display
expect to be spectacle-free, in some patients due to unpredictable
response (over-correction / under-correction / regression), programme of the Oculus Pentacam
postoperative vision may need to be improved further with
additional optical correction. If the symptoms are excessive, an and the nondominant eye corrected for near. This approach has
enhancement procedure can be planned, providing enough corneal been used successfully with contact lens correction.9 If monovision
tissue is available. If at the outset, the refractive error is too high, is suggested as an option, then a two week trial of contact lens
or the cornea is too thin for LASIK, other options such as PRK, monovision should be given prior to refractive surgery to determine
LASEK, epi-LASIK or ICL implantation can be offered. if the patient accepts the compromises inherent in the monovision
strategy. One in four patients will fail to adapt to monovision.
Presbyopes should be informed that additional near vision
correction with glasses will be required after adequate distance Bilateral simultaneous versus sequential surgery: As long as the
vision correction by excimer laser. Presbyopes who expect equally patient does not have unusual risk factors, bilateral simultaneous
good distance and reading vision may not be satisfied with the surgery appears to be safe and offers the advantage of convenience
surgical outcome. to patients. Feared complications which include infectious keratitis
in the central cornea, entry of the microkeratome into the anterior
Choice of treatment (conventional versus wavefront-guided): chamber, corneal melting following a persistent epithelial defect,
Compared to conventional or standard LASIK, wavefront-guided or macular hemorrhage, are fortunately rare. Although sequential
(customized) treatments give better visual outcomes in terms of bilateral LASIK surgery may offer greater flexibility of available
contrast sensitivity, glare and haloes, and night driving. However, options to the patient for the second eye surgery based on the
customized treatments lead to deeper ablations for a given
refractive error. If enough tissue is available, wavefront-guided
treatments would definitely be the procedure of choice, especially
in cases with significant astigmatism, and in those with a greater
proportion of higher order aberrations detected on aberrometry.
If one has access to femtosecond laser, the flap thickness can be
customized to as thin as 90 microns, making more tissue available
for ablation. However, the cost of the procedure would be more.

In patients who have high astigmatism, axis alignment during
surgery is an important issue. Some excimer laser systems, such
as the STAR S4 IR™ (Abbott Medical Optics Inc), have an iris
recognition feature that compensates for cyclotorsion during the
laser ablation. This greatly improves the visual outcome in cases
with significant astigmatism.

Monovision: Monovision is a method of presbyopic correction
whereby the dominant eye is usually corrected for distance vision

52 DOS Times - Vol. 15, No. 4, October 2009

outcome of the first eye, it probably does not in general reduce 3. Laser Vision Correction (LASIK) - Preoperative Considerations.
the risk of a complication in the second eye. Various surgeons Published by University of Illinois Eye & Ear Infirmary.
have reported simultaneous bilateral LASIK to be as safe and www.agingeye.net/mainnews/LASIK.php
effective as sequential surgery.10,11
4. W.W. Haw and E.E. Manche, Effect of preoperative pupil
Informed consent: An important part of the preoperative evaluation measurements on glare, halos, and visual function after
concerns with informing the patient regarding potential risks and photoastigmatic refractive keratectomy. J Cataract Refract Surg
limitations of the surgery as well as providing a copy of the consent 2001:27,907-916.
form for the patient to read, understand and sign. Complications
of refractive surgery are infrequent, and in general occur in less 5. Suzuki S, Oshika T, Oki K, Sakabe I, Iwase A, Amano S, Araie M.
than 5% patients, but nonetheless could cause permanent vision Corneal thickness measurements: scanning-slit corneal topography
sequelae.12 The surgeon should patiently answer the patient’s and noncontact specular microscopy versus ultrasonic pachymetry.
queries and try and alleviate anxieties related to the procedure. J Cataract Refract Surg. 2003 Jul;29(7):1313-8.
Issues regarding symptoms frequently encountered after the
procedure such as dry eyes, grittiness, temporary haloes, as well 6. Schmitt-Bernard CF, Lesage C, Arnaud B. Keratectasia induced by
as the restrictions and the duration of post-operative care should laser in situ keratomileusis in keratoconus. J Refract Surg 2000;
also be discussed beforehand.13 Patients undergoing LASIK for a 16:368-70.
forthcoming social occasion (wedding or engagement) should be
advised to schedule the procedure preferably a month prior to 7. Lafond G, Bazin R, Lajoie C. Bilateral severe keratoconus after laser
the occasion. This would be pertinent especially for the in situ keratomileusis in a patient with forme fruste keratoconus. J
femtosecond procedure, where subconjunctival hemorrhages Cataract Refract Surg 2001; 27:1115-8.
occur more frequently and require time to resolve.
8. Belin MW, Khachikian SS, Ambrósio Jr, R, Salomão M. Keratoconus
It should be understood that refractive surgery is an elective surgery / Ectasia Detection with the Oculus Pentacam: Belin / Ambrósio
that is performed to enhance the quality of life in patients who are Enhanced Ectasia Display. Highlights of Ophthalmology. Volume
dependent of glasses or contact lenses. A carefully performed 35, Number 6.
preoperative examination helps to select individuals in whom a
satisfactory outcome can be reasonably expected. Patients who 9. Jain S, Ou R, Azar DT. Monovision outcomes in presbyopic
have a high risk of developing potential complications or who individuals after refractive surgery. Ophthalmology 2001; 108:1430-
have unrealistic expectations from the surgery are advised against 3.
having refractive surgery.
10. Waring GO 3rd, Carr JD, Stulting RD, Thompson KP, Wiley W.
References Prospective randomized comparison of simultaneous and sequential
bilateral laser in situ keratomileusis for the correction of myopia.
1. Perry HD, Doshi SJ, Donnenfeld ED, Levinson DH, Cameron CD. Ophthalmology. 1999 Apr;106(4):732-8.
Herpes simplex reactivation following laser in situ keratomileusis
and subsequent corneal perforation. Clao J 2002; 28:69-71. 11. Gimbel HV, van Westenbrugge JA, Penno EE, Ferensowicz M,
Feinerman GA, Chen R. Simultaneous bilateral laser in situ
2. Tanzer DJ, Isfahani A, Schallhorn SC, LaBree LD, McDonnell PJ. keratomileusis: safety and efficacy. Ophthalmology. 1999
Photorefractive keratectomy in African Americans including those Aug;106(8):1461-7
with known dermatologic keloid formation. Am J Ophthalmol 1998;
126:625-629. 12. Melki SA, Azar DT. LASIK complications: etiology, management,
and prevention. Surv Ophthalmol 2001; 46:95-116.

13. Ang RT, Dartt DA, Tsubota K. Dry eye after refractive surgery. Curr
Opin Ophthalmol 2001; 12:318-22.

First Author
Ranjan Dutta MD

www.dosonline.org 53

Third Cranial Nerve Palsy Neuro-Ophthalmology

J.L.Goyal MD, DNB, Sudha Seetharam MBBS, Ritu Arora MD, DNB

Third cranial nerve palsy is one of the common neuro- the inferior oblique contains parasympathetic fibres from the
ophthalmological problems presenting to the clinician. The Edinger – Westphal nucleus and supplies the sphincter pupillae
third cranial nerve supplies four out of the six extraocular muscles and ciliary muscle.
along with the Levator Palpebrae Superioris and hence the paresis
of this nerve has a comprehensive effect on ocular motility Causes of Third Nerve Palsy

Anatomy • Microvascular ischaemia due to hypertension, diabetes (most
common cause in adults)
The nuclear complex of the third nerve lies in the mid-brain at the
level of the superior colliculus, ventral to the Aqueduct of Sylvius. • Trauma (most common cause in children and second most
It has the following parts, namely common cause in adults) resulting in extradural or subdural
haematoma which may cause uncal herniation
• The Levator subnucleus is an unpaired structure supplying
both LPS • Aneurysm of posterior communicating artery at its junction
with the internal carotid artery
• The Superior Rectus subnucleii are paired, each innervating
the contralateral superior rectus • Neoplasms

• Medial Rectus, Inferior Rectus, Inferior Oblique subnucleii • Basal meningitis
are paired and innervate the corresponding ipsilateral muscles
• Giant Cell Arteritis
• The Edinger –Westphal nucleus is the caudal parasympathetic
nucleus subserving the papillary reflex • Intracavernous pathology like carotico-cavernous fistula,
cavernous sinus thrombosis, Tolosa Hunt syndrome,
The Fasciculus consists of nerve fibres which pass from the nucleus aneurysm of internal carotid artery etc.
through the red nucleus and the cerebral peduncle to the
interpeduncular space. The Basilar part consists of a set of rootlets • Pituitary apoplexy
which leave the midbrain to form a trunk and traverse through
the subarachnoid space to reach the cavernous sinus. In the Features of Third Nerve Palsy Based on Topography
Cavernous Sinus, the nerve runs in the lateral wall above the
fourth nerve. In the anterior part of the cavernous sinus the nerve Nuclear lesions: Darroff ’s Rule for nuclear third nerve palsy
divides into two parts which enter the orbit through the superior specifies certain condition obligating and excluding nuclear
orbital fissure within the Annulus of Zinn. Within the orbit the involvement. They are
superior division innervates the superior rectus and levator
palpebrae superioris. The inferior division innervates the medial Conditions obligating nuclear involvement:
rectus, inferior rectus and inferior oblique muscles. The branch to
• Bilateral third nerve palsy without ptosis

• Unilateral third nerve palsy with contralateral superior rectus
paresis and bilateral partial ptosis

Figure 1: Anatomy of the third nerve Figure 2: Important causes of isolated
third nerve palsy
Guru Nanak Eye Centre
Maulana Azad Medical College, New Delhi 57

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Conditions excluding nuclear involvement:

• Unilateral ptosis

• Unilateral internal ophthalmoplegia

• Unilateral external ophthalmoplegia with normal contralateral
superior rectus

Fascicular lesions: The syndromes associated with Fascicular
lesions are

Weber’s syndrome

• Involves the cerebral peduncle Hess Chart of Right Third Nerve Palsy
• Ipsilateral third nerve palsy with contralateral hemiparesis

Benedict’s syndrome • Weakness of inferior rectus leading to limitation of depression
• Involves the red nucleus
• Ipsilateral third nerve palsy with contralateral tremors • Unopposed action of superior oblique which leads to intortion
Nothnagel’s syndrome of eye at rest which increases on attempted downgaze
• Involves the superior cerebellar peduncle
• Parasympathetic palsy leading to dilated pupil and defective
accommodation

• Ipsilateral third nerve palsy with contralateral ataxia • Chin elevation, head tilt to same side with face turn to opposite
side
Claude’s syndrome
• Diplopia is generally absent because of ptosis and suppression
• Combination of Benedict’s and Nothnagel’s syndrome due to large deviation

Basilar lesions: The lesions in this area may or may not involve • Aberrant regeneration may occur following trauma,
the pupillary fibres. The pupillomotor fibres are located in aneurysm, neoplasm etc due to breaching of the endoneurium
peripherally and superomedially. They derive their blood supply causing Pseudo Von-Graefe’s sign(elevation of upper lid on
from the pial blood vessels whereas the main trunk of the nerve is attempted adduction or depression) and Pseudo Argyll
supplied by the vasa vasorum. Robertson’s sign(Miosis on attempted adduction or
depression)
Pupil involving third nerve palsy
Investigations
• Surgical lesions like aneurysms, trauma etc involve the pupil
by compressing the pial blood vessels and the superficially In case of elderly patients with non-traumatic third nerve palsy,
located pupillary fibres. assessment of blood pressure, blood sugar, lipid profile of the
patient is to be done. Blood for HbA1C should also be done to
• Generally painful assess long term blood sugar control. A complete blood count
with ESR may e done to rule out giant cell arteritis
Pupil sparing third nerve palsy
For traumatic third nerve palsy, pupil involving palsy in young
• Medical lesions like hypertension, diabetes etc cause patients, neuroimaging is the investigation of choice. Contrast
microangiopathy involving the vasa vasorum involving the enhanced CT Scan of brain or MRI brain should be done to rule
main nerve trunk but sparing the pupillary fibres out aneurysm, tumour, haemorrhage etc

Intracavernous lesions: Lesions in the cavernous sinus involve In addition tests to be done in all cases include
other concurrent structures leading to the following features
• PBCT
• Generally associated with pain
• FDT
• Ipsilateral third, fourth ,fifth and sixth cranial nerve palsies
• Diplopia charting
• Ipsilateral Horner’s syndrome
• Hess’/Lee’s charting
Clinical Features
Management
• Weakness of the LPS leading to ptosis
Patients of third nerve palsy are to be kept under close follow-up
• Weakness of medial rectus and unopposed action of lateral for about 6-8 months and observed for signs of improvement or
rectus leading to limitation of adduction and abducted eye in progression. Generally patients do not have diplopia but if present,
primary position occlusion is done to relieve the same. Surgical management may
be done if residual defects persist even after 6 months duration.
• Weakness of superior rectus and inferior oblique leading to
limitation of elevation

58 DOS Times - Vol. 15, No. 4, October 2009

The goals of surgical management Poor or absent MR function with preserved SR and IR function: MR
resection and LR recession. Resection and transposition of the
• Alignment of eyes in primary position vertical rectii may also be done.
• Relief of diplopia in primary and down position
• Correction of head posture. Preserved MR function with poor or absent IR function: Resection
Complete third nerve palsy: The following surgical options are of IR with or without transposition of the LR to the site of IR can
available be carried out to correct deviation in the primary and down gaze.
Maximum MR resection (8.0 mm) with LR recession (10-12mm)
Surgery for ptosis: Ptosis should be corrected to cover half of the
cornea with relaxed brow.Because of impaired bell’s chances of
exposure keratitis are always there.

Superior Oblique transposition:The procedure was described by References
Peter and Jackson. The trochlea is fractured, the superior oblique
tendon is removed, advanced and attached to the sclera near the 1. Tiffin PA, MacEwen CJ, Craig EA, Clayton G. Acquired palsy of the
insertion of the MR muscle. By placing the muscle in this position, oculomotor, trochlear and abducens nerves. Eye 1996; 10 (Pt 3):377–
the secondary abducting and depressing forces of the superior 384.
oblique are eliminated and changed to adduction which counters
lateral rectus function. This process is technically difficult and may 2. Bennett JL, Pelak VS. Palsies of the third, fourth, and sixth cranial
lead to consecutive hypertropia. A modified technique was nerves. Ophthalmol Clin North Am 2001; 14:169–185.
suggested by Scott who advised transposition of the superior
oblique tendon without involving the trochlea.Superior oblique 3. Bianchi-Marzoli S, Brancato R. Third, fourth, and sixth cranial nerve
can be disinserted shortened by 12mm and reinserted to the medial palsies. Curr Opin Ophthalmol 1997; 8:45–51.
rectus. Residual vertical residual deviation may be corrected by
weakening inferior rectus muscle in the other eye or traspositioning 4. Rush JA. Causes and prognosis in 4,278 cases of paralysis of the
horizontal recti superiorly. oculomotor, trochlear, and abducens cranial nerves. Am J
Ophthalmol 1992; 114:777-778.
Surgery on the other eye: In this case, the non-involved eye of the
patients is moved towards an adducted position and thus abducting 5. Gupta D, Vishwakarma SK. Superior orbital fissure syndrome in
impulses are needed to gaze straight ahead. According to Herring’s trigeminofacial zoster. J Laryngol Otol 1987; 101:975–977
law, this process will stimulate the medial rectii of the paralysed
eye. 6. Lepore FE. False and non-localizing signs in neuro-ophthalmology.
Current Opinion in Ophthalmology 2002, 13:371–374

7. Walsh, Hoyt. Clinical Neuro-Ophthalmology. 5th Ed.
Baltimore:Williams and Wilkins, 1998, 5107.

Partial third nerve palsy: The following surgical options are available 8. Albert, Jakobiec,Azar et al. Principles and Practice of
Ophthalmology.2nd Ed. 2000,4011-21.

First Author
J.L. Goyal MD, DNB

www.dosonline.org 59

Ganglion Cell Comlex: A Newer Diagnostic Aid in Glaucoma
Pre-Perimetric Glaucoma

Suneeta Dubey MS, Baswati Prasanth MS DNB, Monica Gandhi MS, Julie Pegu MS, Parmod Kumar B.Sc

Glaucoma has been redefined by the American Academy of from each of these regions can be used to differentiate between
Ophthalmology as an optic neuropathy with characteristic normal and glaucomatous eyes3-11. Each of the ocular scanning
structural damage to optic nerve, associated with progressive retinal regions has its own theoretical advantages that make it the
ganglion cell death, loss of nerve fibers and visual field loss. preferable scanning area. ONH and peripapillary regions are the
Glaucomatous optic neuropathy is characterized by structural locations where nerve fibers from throughout the eye are
changes in the optic disc in the form of thinning of neuroretinal represented. The retinal ganglion cell (RGC) layer in the macula is
rim, pallor and progressive cupping of the optic disc. Disc more than one cell thick, and RGC bodies have 10 to 20 times the
hemorrhages with associated retinal nerve fiber layer defects diameter of their axons. Also, the macular region contains over
precede measurable changes of the optic disc configuration1.The 50% of all retinal ganglion cells. Because the RGC layer and the
functional changes accompanying the structural damage includes NFL are layers prone to glaucomatous damage, macular scanning
visual field defects. Unfortunately, in glaucoma the structural has been suggested an ideal region to detect early cell loss and
changes precedes the functional damage and field changes are changes over time because of the high density of cells12,13.
often detected only after 40% of the axons are lost2. This fact lays
an emphasis on the diagnosis of preperimetric glaucoma. Ganglion cell complex (GCC)

Pathophysiology of Glaucoma Ganglion cell complex comprises of:

The pathophysiology of glaucoma is believed to be multifactorial. • the retinal nerve fiber layer (NFL) made up of the ganglion
The initial insult to glaucomatous atrophy is either mechanical in cell axons
form of elevated intraocular pressure (IOP) or vascular as a result
of an altered optic nerve microcirculation at the level of • the ganglion cell layer (GCL) made up of the ganglion cell
laminacribrosa. Other accompanying factors that lead to secondary bodies, and
damage include excitotoxic factors like glutamate or glycine
released from injured neurons and oxidative damage caused by • the inner-plexiform layer (IPL) made up of the ganglion cell
over-production of nitric oxide (NO) and other reactive oxygen dendrites
species. Whatever may be the primary and secondary factors, the
end result in glaucomatous eyes is the dysfunction and death of All three layers, collectively known as the ganglion cell complex
Retinal Ganglion Cells leading to irreversible visual loss. (GCC), become thinner as the ganglion cells die from glaucoma
(Figure 1).
Current diagnostic tools
Fourier domain OCT( FD-OCT) Vs Stratus OCT
Researchers have long been battling to detect this sneak thief of
sight at the earliest as currently there is no cure to glaucoma. The Two parameters differentiate Time-domain (the Stratus OCT) and
effort is to rescue the ganglion cells and to delay or stop vision loss Fourier-domain OCT: Speed and Resolution. The FD-OCT system
by keeping the intraocular pressure under control, the sooner the by virtue of its high speed performs 26,000 A-scans per second, as
better. This has revolutionsed the need for new tools thereby compared to 400 A-scans per second by the Stratus OCT. Fourier-
detecting pre-perimetric glaucoma with the aid of current diagnostic domain OCT uses a stationary reference mirror and a spectrometer
techniques. The various computer imaging techniques presently to capture information from all layers of the retina
available are scanning laser polarimetry (GDx,VCC/FCC), confocal simultaneously in contrast to the time-domain OCT systems which
laser ophthalmoloscopy (Heidelberg Retinal Tomography) and
optical coherence tomography (OCT) where the Fourier domain
OCT is the latest iteration.

Optical Coherence Tomography (OCT) is a high-resolution
noncontact imaging modality. The ocular application of this
technology provides quantitative measurements of the macular
retinal thickness, peripapillary nerve fiber layer (NFL) thickness,
and topographical measurements of the optic nerve head (ONH).
Cross-sectional studies have shown that measurements obtained

Figure1: Ganglion cell complex

Shroff Charity Eye Hospital, 61
Kedarnath Road, Daryaganj, New Delhi

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Figure 2: Normal Eye Glaucomatous Eye depend on the mechanical movement of a reference mirror to
measure the reflectance from various layers of the retina. The
Figure 3: Deviation Map in Fourier-domain (FD-OCT) system also employs a higher spectral
glaucomatous eye showing 20-50% bandwidth light source, which provides a finer axial resolution of
5μm—a twofold improvement over the conventional time-domain
loss of retinal ganglion cells Stratus OCT.

GCC analysis : The GCC scan data encompasses

Thickness map: The GCC thickness values are analyzed and
compared to a normative database which is made up of over 300
healthy eyes from various ethnicities with an age range from 18-
80. The normative database provides the clinician the status of the
patient relative to an age-matched individual. If the patient’s values
are outside the normal range, the measurement is color-coded
appropriately. The thickness map is color coded where thicker
regions are displayed in hot colors (yellow & orange), and thinner
areas are displayed in cooler colors (blue & green). Thickness map
in a case of a normal and glaucomatous eye is shown in the fig
below (Figure2).

Deviation Map: The Deviation Map shows the percent loss from
normal. This map is calculated by taking the actual value from a
scan at each pixel location in the map, subtracting the normal
value, and then dividing that by the normal value. The result is a
percent loss value at each pixel location in the map. The map is
color coded where blue represents GCC thinning from 20-30%
relative to normal and black color represents a 50% loss or greater,
relative to an age-matched normal (Figure 3).

Significance Map: The significance Map shows regions where the
change from normal reaches statistical significance. The
Significance Map is color-coded where green represents values
within the normal range (p-value 5%-95%), yellow indicates a
Borderline results (p-value < 5%), and red represents an Outside
Normal Limits (p-value< 1%) (Figure 4).

A parameter table is also provided for the GCC analysis. The
table consists of the average.

GCC thickness, Superior GCC thickness, and Inferior GCC
thickness. All parameters are compared to the normative database
and color coded accordingly.

Section OD OS

Avg GCC (μm)
Sup GCC (μm)
Inf GCC (μm)

Figure 4: Significance Map showing Focal Loss Volume (FLV): Focal Loss Volume (FLV) is a new
percentile loss of retinal ganglion cells parameter that provides a quantitative measure for the amount
of significant GCC loss. FLV is the total sum of significant GCC
loss (in volume) divided by the map area.

Clinical Application

Fourier Domain OCT is relatively new with very few studies
published in peer reviewed Journals so far. Macular scanning
provided quantitative measurement of the entire retinal volume
and thickness, whereas the circumpapillary scans provided
thickness of the nervefibre layer, which is specifically prone to

62 DOS Times - Vol. 15, No. 4, October 2009

glaucomatous damage. Measurement of the entire retinal thickness loss (Figure 6). In a cross sectional observational study by Huang
might be less sensitive in the detection of glaucomatous damage. et al (article in press),the average GCC measurements with FD-
Ganglion cell analysis with the help of Fourier Domain OCT have OCT was higher than the macular thickness in preperimetric
attempted to differentiate between macular layers and thus more glaucoma cases as compared with normal eyes but the difference
directly measure the thickness of the RGC and NFL, which are was not statistically significant. The author presumed the smaller
both prone to glaucomatous damage. Two recent studies have sample size for this insignificant corerelation.18
found that glaucoma diagnostic accuracy could be improved if
macular measurements by OCT are focused on the inner retinal Conclusion
layers.14,15 In a study, Takagi and colleagues showed that the GCC
analysis significantly detected GCC thinning in eyes with visual The concept of imaging the macula for glaucoma is not of recent
field defects in one hemisphere and significantly correlated with origin. Especially because glaucoma is a disease defined by clinical
the severity of visual field loss.16 In another study, Mori et al found appearance of the optic nerve and visual field, objective and
that the GCC analysis significantly differentiated normal from quantitative measures could potentially provide a more accurate
glaucoma and had an Area under the ROC (receiver operating and precise method for the diagnosis of glaucoma and detection
characteristic curves) of 0.91. The GCC analysis also significantly of its progression. Structurally, the macula with its highest
correlated with visual field damage.17 A similar correlation was concentration of ganglion cells seems to be a logical place to look
obtained at this centre. In diagnosed cases of glaucoma, GCC at changes in the RNFL and GCC. However, measuring the total
analysis when done correlated with the visual field loss (Figure 5). thickness of the macula with spectral OCT technology does not
provide sensitive information about glaucomatous change, as the
In a case of preperimetric Glaucoma, where the patient showed a disease preferentially affects the inner retinal layer. Fourier-domain
raised IOP in left eye with disc asymmetry and the Visual fields OCT can quantify the thickness of the macula in microns by virtue
(Humphrey’s 24-2 SITA STANDARD) were essentially normal; of its higher depth resolution. This degree of precision allows to
OCT and GCC analysis showed significant retinal ganglion cell detect small, consistent changes in the RNFL that cannot be

Figure 5: Significance map, NHM4 and Corresponding visual fields (Humphrey’s 24-2 SITA 63
STANDARD) and stereoscopic disc photographs in a case of normotensive glaucoma

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Figure 6: Significance map, NHM4 and corresponding visual fields
(Humphrey’s 24-2 SITA STANDARD) in a case of preperimetric glaucoma

visualized with even the best quality stereophotographic fundus fiber layer thickness in normal and glaucomatous eyes using optical

photographs. The concept of GCC analysis is new with anecdotal coherence tomography. Arch Ophthalmol 1995;113:586 –596.

reports in peer reviewed journals. The significant corroboration 4. Mistlberger A, Liebmann JM, Greenfield DS, et al. Heidelberg retina

with the visual fields provides an insight to this technique of retinal tomography and optical coherence tomography in normal, ocular-

ganglion cell analysis holding a promising future in the diagnosis hypertensive, and glaucomatous eyes. Ophthalmology 1999;106:

of preperimetric glaucoma. However due to paucity of long term 2027–2032.

studies on ganglion cell analysis, prospective studies might be required 5. Pieroth L, Schuman JS, Hertzmark E, et al. Evaluation of focal

to validate this novel approach as a routine investigative tool for the defects of the nerve fiber layer using optical coherence tomography.

diagnosis of preperimetric glaucoma. Currently, however it can be Ophthalmology 1999;106:570 –579.

used to boost up the diagnostic accuracy in preperimetric glaucoma 6. Bowd C, Weinreb RN, Williams JM, Zangwill LM. The retinal nerve

along with the RNFL analysis. fiber layer thickness in ocular hypertensive, normal, and

References glaucomatous eyes with optical coherence tomography. Arch
Ophthalmol 2000;118:22–26.

1. Airaksinen PJ, Alanko HI. Effect of retinal nerve fibre loss on the 7. Hoh ST, Greenfield DS, Mistlberger A, et al. Optical coherence

optic nerve head configuration in early glaucoma. Graefes Arch tomography and scanning laser polarimetry in normal, ocular

Clin Exp Ophthalmol 1982;220:193-6. hypertensive, and glaucomatous eyes. Am J. Ophthalmol

2000;129:129 –135.

2. Quigley HA, Dunkelbarger GR, Green WR. Retinal ganglion cell 8. Zangwill LM, Williams J, Berry CC, et al. A comparison of optical
atrophy correlated with automated perimetry in human eyes with coherence tomography and retinal nerve fiber layer photography
glaucoma. Am J Ophthalmol 1989;107:453-64. for detection of nerve fiber layer damage in glaucoma.

3. Schuman JS, Hee MR, Puliafito CA, et al. Quantification of nerve Ophthalmology 2000;107:1309 –1315.

64 DOS Times - Vol. 15, No. 4, October 2009

9. Bowd C, Zangwill LM, Berry CC, et al. Detecting early glaucoma by 14. Ishikawa H, Stein DM, Wollstein J et al..Macular segmentation

assessment of retinal nerve fiber layer thickness and visual function. using optical coherence tomography. Invest Ophthalmol Vis Sci

Invest Ophthalmol Vis Sci 2001;42: 1993–2003. 2005;46:2012-7.

10. Kanamori A, Nakamura M, Escano MF, et al. Evaluation of the 15. Tan O, Li G, Lu AT et al. Mapping of Mavular substructures with
glaucomatous damage on retinal nerve fiber layer thickness measured optical coherence tomography for Glaucoma Diagnosis.
by optical coherence tomography. Am J Ophthalmol 2003;135:513– Ophthalmology 2008;115: 949-56.
520.
16. Takagi, A. Nose, Y. Kita, G. Tomita. Inner Retinal Layer
11. Guedes V, Schuman JS, Hertzmark E, et al. Optical coherence Measurements in Macular Region with Fourier Domain Optical
tomography measurement of macular and nerve fiber layer thickness Coherence Tomography in Glaucomatous Eyes With Hemifield
in normal and glaucomatous human eyes. Ophthalmology Defects. IOVS, Suppl. 4648: 2008.
2003;110:177–189.
17. S. Mori, M. Hangai, H. Nakanishi, Y. Kotera, R. Inoue, S. Morishita,
12. Zeimer R, Asrani S, Zou S, et al. Quantitative detection of Y. Aikawa, F. Hirose, T. Ojima, N. Macular Inner and Total Retinal
glaucomatous damage at the posterior pole by retinal thickness Volume Measurement by Spectral Domain Optical Coherence
mapping. A pilot study. Ophthalmology 1998;105:224–231. Tomography for Glaucoma Diagnosis. IOVS Suppl. 4651: 2008.

13. Greenfield DS, Bagga H, Knighton RW. Macular thickness changes 18. Ou Tan, Vikas Chopra, Ake-Tzu-Hui, Joel Schuman, David Huang.
in glaucomatous optic neuropathy detected using optical coherence Detection of Macular Ganglion Cell loss in Glaucoma by Fourier–
tomography. Arch Ophthalmol 2003;121:41–46. Domain Optical Coherence Tomography. Article in press,
Ophthalmology 2009.

First Author
Suneeta Dubey MS

Monthly Clinical Meetings Calendar 2009-2010

Dr. R.P. Centre for Ophthalmic Sciences Venu Eye Institute & Research Centre
26th July, 2009 (Sunday) 29th November, 2009 (Sunday)
Safdarjung Hospital
Shroff Charity Eye Hospital 27th December, 2009 (Sunday)
23rd August, 2009 (Sunday) Bharti Eye Foundation
31th January, 2010 (Sunday)
Base Hospital
4th October, 2009 (Sunday) Centre for Sight
28th February, 2010 (Sunday)
Sir Ganga Ram Hospital Guru Nanak Eye Centre
1st November, 2009 (Sunday) 28th March, 2010 (Sunday)

Midterm Conference of DOS
14th & 15th November, 2009 (Saturday - Sunday)

Annual Conference of DOS 16th-18th April, 2010 (Friday, Saturday & Sunday)

www.dosonline.org 65

Management of Posterior Capsular Tear: Clinical Meeting: Clinical Talk
A Vitreo-retinal Surgeon’s Perspective

Neeraj Manchanda DO, DNB, S.N. Jha MD, Amit Khosla MD, H.K. Tewari MD, Nidhi Tanwar MD

Phacoemulsification is the accepted standard for cataract Of particular note are posterior polar cataracts where, even in
extraction. Posterior dislocation of lens fragments into the experienced hands, a posterior capsular rupture rate of between
vitreous is one of the recognised complications of 11% and 36 % is reported.
phacoemulsification that may compromise final visual outcome
and has an incidence of between 0.3% and 1.1%. Management

Here we aim to discuss the mechanism, risk factors and The management of the displaced nucleus can be divided into two
management options for displaced nuclear fragments. parts:

Mechanism 1. Initial management by the cataract surgeon

Displaced nuclear fragments most often result from a large posterior 2. Later management by the vitreoretinal surgeon.
capsular tear, although more rarely they occur following zonular
dialysis. Several surgical steps may be contributory to a posterior Management by the cataract surgeon
capsular tear.
The experienced cataract surgeon may be competent to continue
1. Radial anterior capsular tear formation during capsulorhexis, with surgery in the presence of anterior capsular tears and even
which then proceeds to extend posteriorly, is a common large posterior capsular tears. However, once it has been identified
precursor. that a nuclear fragment has dropped into the vitreous cavity, it
should be recognised that referral to a vitreo-retinal surgeon will
2. Anterior capsular tear may also result from damage with the be necessary. The key consideration at this point is that the situation
phaco tip, particularly when the capsulorrhexis is small or is still entirely salvageable.
irregular.
Appropriate management of the case by a vitreo-retinal surgeon
3. Direct perforation of the posterior capsule with the phaco is likely to result in a good visual outcome. However, inappropriate
probe may occur during deep sculpting or during nucleus
removal, where there is inadequate protection of the capsule
with the second instrument or following continued aspiration
after fragment removal (Figure 1).

4. Less commonly capsular rupture may occur on
hydrodissection, particularly in the presence of a posterior
polar cataract.

Risk factors

Surgical cases that offer the cataract surgeon a ‘challenge’ are more
likely to result in loss of the capsulorhexis or later capsular tears.
Late recognition of such tears is usually an identifiable factor in
cases with a displaced nuclear fragment.

For the novice surgeon the risk of this complication is increased
even in the seemingly straightforward case. Signs of impending
nucleus drop include sudden deepening of the anterior chamber,
inability to rotate the nucleus , dipping of the nucleus edge, and
altered reflex in the periphery As the surgeon gains a little more
experience and is confident in routine cases, both trainee and
trainer should be particularly vigilant in cases likely to provide
challenge. Examples would include cases with corneal scarring,
small pupil, dense nucleus or previous vitrectomy. Some cases will,
of course, provide a challenge even to the experienced surgeon.

Figure 1: Nucleus drop by PCT with a phaco probe

Department of Ophthalmology 67
Sir Ganga Ram Hospital, Rajinder Nagar, Delhi

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and/or inexperienced intervention may result in serious
complication, which will compromise the outcome. The cataract
surgeon should therefore resist the temptation to ‘chase’ nuclear
fragments or perform procedures outside his/her expertise.

1. An anterior vitrectomy, preferably with separate irrigation
cannula or anterior chamber maintainer, should be performed
to clear the wound.

2. The section should be checked externally to ensure it is free
from vitreous strands.

3. A complete anterior vitrectomy can be performed, together Figure 2: Anterior Vitrectomy
with removal of the remaining soft lens matter, which can
also be cleared with the suction cutter (Figure 2, 3).

4. It is essential to retain good capsular support, and if this
procedure proves difficult it should be left for the vitreo-
retinal surgeon who may be able to get clearance more easily
from a posterior approach.

5. Where there is an intact capsulorrhexis a foldable lens can be
placed in the ciliary sulcus and capture of the optic by the
capsulorrhexis may be used to stabilise the lens.

6. At the end of the procedure it should be ensured that the
wound is secure.

7. A sub-conjunctival steroid injection can be given and the
patient should be commenced on regular topical steroids,
antibiotics and a mydriatic.

8. Non-steroidal anti-inflammatory drops appear to be beneficial
for the prophylaxis of cystoid macular oedema.

9. The intraocular pressure should be closely monitored and
managed medically as appropriate. Early referral to the vitreo-
retinal surgeon should be made to allow flexibility with regard
to subsequent management.

Management by the vitreo-retinal surgeon

The vitreo-retinal surgeon will assess the patient and make a judgement Figure 3: Vitrectomy Machine
about the amount of lens matter present and the speed at which
further intervention is required.

1. If there are anterior retinal tears or early retinal detachment, 2. However, even small fragments can be associated with
early intervention is indicated. inflammation, glaucoma and cystoid macular oedema and if
a conservative course of action is taken, the patient should be
2. Similarly, if intraocular pressure cannot be controlled by closely observed.
medical means, or if there is a marked inflammatory response,
early intervention will be beneficial. Our practice is to perform vitrectomy to remove any nuclear
fragment.
3. Otherwise, a short delay may aid surgery due to resolution of
corneal oedema and acute postoperative inflammation. 1. Vitrectomy should be a standard three-port pars plana
vitrectomy.
4. Delay may also allow the retained lens material to soften,
which may aid its removal. 2. Use low suction (50-100 mm Hg) and high cut rate ( 600/
min).
Several studies have shown a higher incidence of long-term
complications such as uveitis, glaucoma and corneal oedema with 3. Lens pieces and blood should be freed of vitreous.
delayed surgery, particularly where surgery is delayed by more than
four weeks. The aim should be to operate in the first 2 weeks. 4. A posterior vitreous detachment must be induced if it is not
already present and vitreous should be removed from around
1. Small fragments may not cause significant inflammation and the lens fragments to minimise retinal traction.
may eventually be reabsorbed if left. This has led to a belief
that nuclear pieces of size less than 25% of the whole nucleus 5. If the lens matter is soft it can be removed with the vitreous
can be managed conservatively. cutter.

68 DOS Times - Vol. 15, No. 4, October 2009

8. Some surgeons use PFCL to lift up the nucleus from retina
and set it afloat in the vitreous cavity to ease its removal.
(Figure 4 )

9. To guard against retinal damage from traction produced by
fragmatome aspiration of residual vitreous, a thorough
vitrectomy must be performed before removal of lens matter.

10. Nuclear fragments should be brought into the mid-vitreous
cavity before ultrasound is applied. The vitreo-retinal surgeon
must finally ensure that no nuclear fragments remain in the
vitreous base and that there are no retinal tears.

11. If conditions are favourable after vitrectomy and fragment
removal, an intraocular lens implant can be inserted ( if not
present already).

12. A posterior chamber implant into the ciliary sulcus, where
capsular support is sufficient, is a good option.

13. Where there is doubtful capsular support, an iris-sutured or
scleral-sutured lens may be indicated.

Conclusion

In summary, a dropped nucleus is a serious complication of cataract

surgery. However, the most important predictor of good final

visual acuity is a minimally complicated clinical course (eg. absence

Figure 4: Dropped nucleus removal aided by PFCL of suprachoroidal haemorrhage, retinal detachment or cystoid
macular oedema). The cataract surgeon should therefore seek to

minimise further complication, avoiding the temptation to attempt

to remove dropped nuclear fragments and, following appropriate

6. Otherwise ultrasonic fragmentation, using a anterior vitrectomy, make early referral to the vitreoretinal
surgeon.
phacofragmatome can be used.

7. Use phacofragmentome needle without sleeve. Use of
endoilluminator as chopper is advocated.

First Author
Neeraj Manchanda DO, DNB

www.dosonline.org 69