Contents
E5 ditorial Retina
Focus 69 Retinal Pigment Epithelial Tear
7 Neovascular Age Related Macular Degeneraton: After Intravitreal Anti-VEGF Injection
Atul Kumar, Subijay Sinha, Yog R. Sharma, Raj V. Azad
Role of Anti-VEGF Drugs
Ophthalmoplasty
Cataract : Phacoemulsification for Beginners 71 Orbitotomy
13 Wound Construction Noornika Khuraijam, Neelam Pushkar, Mandeep Singh Bajaj
Shalini Mohan, Sudarshan Khokhar, Anand Aggarwal, Anita Panda Squint
23 Capsulorhexis 77 Measurement of Stereoacuity
Tanuj Dada, Harinder S. Sethi, Munish Dhawan, Rohit Saxena, Vimla Menon
Vivek Dave, Kiran G. Krishnan
Photo Essay
29 Hydro Procedures
79 Post Operative Malignancy
Tushar Agarwal, Asim K. Kandar, Namrata Sharma
Gopal S Pillai, Niranjan Pehere, Anuradha Rao, Meenakshi Dhar
33 Basic Phacodynamics
Industry News
Archana Sood, Parul Sony, Satish C. Gupta
83 Contact Lens Solution Related Acanthamoeba
41 Nuclear Emusification
Keratitis-‘Alert’
Asim K. Kandar, Namrata Sharma, Jeewan S. Titiyal Vishal Jhanji
47 Phaco Chop Techniques – Horizontal vs. Vertical Chop
David F. Chang
51 Cortical Irrigation Aspiration
Shetal M. Raj, Abhay R. Vasavada
Referactive Surgery A85 bstracts
57 Femtosecond Laser R87 emembrance
Mahipal S. Sachdev, Deepender Chauhan Columns
Cornea 88 DOS Quiz
61 Sutureless DSAEK Saurabh Sawhney, Ashima Agarwal
Rasik B. Vajpayee M93 embership Form
63 Modified Osteo-Odonto-Keratoprosthesis F98 orthcoming Events
Ramendra Bakshi, Vinay S. Bhaskar Srinivasan,
Geetha K. Iyer, G. Sitalakshmi
Tearsheet
Phacoemulsicfication Machines
Samir Kaushal
Editorial
Namrata Sharma
Secretary,
Delhi Ophthalmological Society
Dear Members
I would like to thank you first for your whole hearted support and best wishes in nominating me as a secretary to this office.
A new look has been given to the DOS Times. Two sections will be featured in every issue - Focus which is an interactive interview based
article in which the eminent ophthalmologists will give their viewpoint and a theme topic on which the issue will be based. In this era of
multi media technology we have to change with the times. In order to transfer skill and knowledge we have started distribution of CD s
which we hope to bring out in every other issue under the aegis of Delhi Ophthalmological Society. This time we have included the CD
on “Phacoemulsification for Beginners” and I am grateful to all the eminent surgeons who have generously contributed their surgeries.
We also hope to give video CDs of other common corneal, retinal, squint, glaucoma and ophthalmoloplasty surgeries from time to time.
Brilliant work has been done by previous secretaries so that the bar for the annual and mid term conferences of the Delhi
Ophthalmological society have been raised. We will continue the same and take the society to even greater heights so that we make
a mark in the international forum. We hope to invite international faculty members so that the common member has international
exposure. Academically rich symposia, interactive sessions and video assisted courses along with live surgeries will be organized in
our conferences. This would cover both the basic techniques as well as the recent advances.
In order to support the aspect of quality eye care a number of materials will also be produced to help the ophthalmologists in clinical
decision-making process. The cornerstone of this program will be the “Practice Guidelines Series” which will provide a series of
guidelines to identify the characteristics and components of quality eye care.
Very soon patient education publications, public information campaigns to promote eye health and safety will also be released
along with the DOS Times.
By now you may have encountered the new look of website which in future will be made very interactive.
Please feel free to give any suggestions for the improvement of the DOS. I am looking forward to your co-operation to enable the
society to reach the greatest heights.
Namrata Sharma
Secretary ,
Delhi Ophthalmological Society
Neovascular Age Related Macular Degeneraton: Focus
Role of Anti-VEGF Drugs
Philip J. Rosenfeld Pran N. Nagpal MD Raj V. Azad MD, DNB H.K. Tewari MD Lalit K. Verma MD Dinesh Talwar MD
MD, PhD
Age related macular degeneration (AMD) is a common cause of visual loss in aging population. In fact AMD is the leading cause of
legal blindness among elderly patients in developed countries.
The number and variety of treatment options for choroidal neovascularization (CNV) have grown tremendously in the last several
years. Advances in our understanding of angiogenesis have facilitated the development of drugs specifically directed against
neovascularization. The most widely studied target has been vascular endothelial growth factor (VEGF), which plays a central role in
the complex cascade of vessel growth, proliferation, and hyperpermeability.
Till recently PDT was the standard treatment for CNV due to AMD. Pegaptanib sodium emerged as the first antiangiogenic agent
with proven efficacy in clinical trials for neovascular AMD. Then came ranibizumab, a humanized monoclonal antibody fragment
against VEGF that has proven efficacy in the treatment of subfoveal CNV due to AMD. However, in recent years many ophthalmologists
are using its parent compound, bevacizumab, as an off-label treatment for neovascular AMD, with encouraging short-term effects.
We tried to find out how the above mentioned agents could be optimally utilized for best results in neovascular AMD patients.
Professor Rosenfeld (PR) introduced intravitreal bevacizumab (avastin) for the first time in ophthalmology. Prof. P. Nagpal (PN), Prof.
R.V. Azad (RVA) and Dr. L.K. Verma (LKV) have also been using many anti-VEGF agents for the treatment of their AMD patients.
These leading ophthalmologists were asked for their opinion regarding the use of anti-VEGF agents in the treatment of AMD patients.
PR: Prof. Rosenfeld, Boscom Palmer Eye Institute, Department of Ophthalmology, University of Miami, School of Medicine, FL,
USA, PN: Prof P N Nagpal, Retina Foundation, Ahemdabad India, RVA: Prof Raj Vardhan Azad, Dr. Rajendra Prasad Centre for
Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, Retina Mangement Group : Prof H.K. Tiwari,
Dr. Lalit Verma, Dr. Dinesh Talwar, Senior Consultants, Centre for Sight, New Delhi, SM: Dr. Subrata Mandal, Dr. Rajendra Prasad
Centre for Ophthalmic Science, All India Institute of Medical Sciences, New Delhi
SM: What treatment do you prefer in neovascular AMD? coverage and I use Avastin when patients have to pay a
Monotherapy or combination therapy? portion or all of their treatment. Of course, all treatments
are performed following a full and complete consent
PR: The best treatment for neovascular AMD is pan- process, and I even have some patients with insurance
VEGF-A inhibition. The most convincing efficacy and who elect to receive Avastin because, in principle, they
safety information comes from the MARINA and feel the cost of Lucentis is too high. So far, I have not had
ANCHOR trials using intravitreal ranibizumab (Lucentis). any patients who have to pay for the treatment choose
However, Lucentis is expensive at over $2000 a dose in Lucentis over Avastin. When patients have to pay, it seems
the U.S. A low cost alternative to Lucentis is intravitreal reasonable to start with Avastin then switch to Lucentis if
bevacizumab (Avastin). We have had great success using the results are not as good as expected. So far, I’ve had
intravitreal Avastin for the treatment of neovascular AMD one patient switch, but the results with Lucentis were no
and other diseases characterized by neovascularization better, so the patient switched back to Avastin. In the
and exudation. To determine whether Lucentis and future, if Avastin is shown to be safe and to have efficacy
Avastin are comparable with respect to safety and efficacy, comparable to Lucentis, then I see Avastin as the
we await the results of the CATT and IVAN trials from preferred first-line therapy.
the U.S. and U.K., respectively. These studies are We use only Monotherapy with anti-VEGF. Only
prospective randomized clinical trials comparing Avastin PN: occasionally we have used anti-VEGF in combination
to Lucentis for the treatment of neovascular AMD, and with IVTA. These were cases with subretinal membranes
these trials should start in the second half of 2007. Until with large collection of sub-retinal fluid.
the 1 year results of these trials are available in 2009, Difficult to comment. Depends on size and type of CNV.
many of our treatment decisions will be guided by the RVA: In a small classic lesion, I prefer monotherapy with PDT
economics of anti-VEGF therapy. In the US right now, whereas in large minimally classic / occult lesion, I prefer
I usually use Lucentis to treat patients with full insurance
7
www.dosonline.org
RMG: monotherapy with anti-VEGF. However, In a large classic PN: We have used IVTA in combination with anti-VEGF in
lesion I will prefer combination therapy. RVA: cases that show significantly large sub-retinal fluid
SM: Depends on type of membrane, its size and visual acuity. RMG: accumulation.
PR: We are presuming that we are discussing subfoveal SM: PDT and lucentis. Where as lucentis decreases leakage
membranes. In classic membrane, we will prefer PR: from CNV, PDT aims at closure of the same.
PN: combotherapy- low fluence PDT and anti-VEGF specially Low fluence PDT with Lucentis.
RVA: if visual acuity is good. However in occult membrane, we PN:
RMG: prefer monotherapy with anti-VEGF. RVA: Since when you have been using anti-VEGF agents? How
In monotherapy, what do you prefer and why? PDT or RMG: many injection you give in a month?
Anti-VEGF or IVTA? SM: I started injecting Lucentis in the phase I study in 2001 so
I only use anti-VEGF therapy for neovascular AMD. Our PR: we have at least 6 years of anti-VEGF therapy. Now, I
experience and the available data strongly suggest that perform at least 100 injections a week. Last year at the
most patients lose vision over time with Macugen, PDT, PN: Bascom Palmer Eye Institute we performed over 7000
and IVTA, while Lucentis therapy has been shown to RVA: injections and that number will probably be close to
give patients their best chance of vision improvement. RMG: 10,000 this year. We perform a lot of injections.
However, not all patients improve vision while on SM: We have been using anti-VEGF since February 2006. We
Lucentis, and I would suspect that those same patients PR: give on an average 30 anti-VEGF injections per month of
who lost vision on Lucentis would have lost even more which about 15 are for AMD (last 4 months data).
vision on PDT, IVTA, or Macugen. PN: I have been using avastin for 1.5 yrs and lucentis for 4
We use anti-VEGF therapy. The results of PDT have not RVA: months. I give approximately 50 Avastin inj/month and
been so favourable and the cost becomes a major limiting RMG: 4 lucentis inj/month.
factor. SM: For last 15 months, we give approximately 10 Lucentis
Anti-VEGF. In comparison to anti-VEGF, results of PDT PR: and 30 avastin per month.
are not that good. I don’t use IVTA as monotherapy.
Anti-VEGF in overall. If pure classic then PDT but will PN: Which anti-VEGF would you prefer to use if cost is not
add anti-VEGF after few days. We do not give IVTA. a concern?
My preference would be Lucentis simply because we have
We will prefer combotherapy- more prospective safety and efficacy data. Unfortunately,
low fluence PDT and anti-VEGF whether we like to admit or not, cost is always a concern. In
specially if visual acuity is good. the U.S., we have to balance cost, efficacy, safety, and the
However in occult membrane, medico-legal consequences of using drugs off-label. It’s a
delicate balancing act, and the most important step in the
weprefer monotherapy process is to have a good relationship with your patient
with anti-VEGF and to keep them fully informed about the treatment
decision process. The consent process is very important.
SM: If you want to use combination therapy, what We would prefer to use Lucentis (Ranibizumab) if cost is
combination is most effective according to you? not a factor.
Lucentis
PR: If you mean that combination therapy is effective by Lucentis.
resulting in better visual acuity outcomes, I don’t think
there is any data to suggest that the vision outcomes are Where do you give intravitreal injection? As OPD/
better with combination therapy. The FOCUS Study Office, Minor OT or major OT procedure?
from Genentech showed the visual acuity outcomes We give injections right in clinic as we are seeing patients.
appeared worse. The only benefit of combination therapy We have nurses or a technician who is an “injection specialist”
is that it may decrease the need for repeated intravitreal prep the patient by inserting a sterile lid speculum and
injections. However, combination therapy needs to be applying topical lidocaine and betadine. I have never had a
compared with prn dosing with Lucentis or Avastin. case of endophthalmitis after thousands of injections.
In our prn dosing study called PrONTO, we found that We give the injections in the Major OT.
the average number of injections over 2 years was 10 Major /minor OT procedure.
with some patients needing fewer injections and some Major or minor OT with standard sterile precautions.
needing more injections. When I have tried combo What is your follow up protocol after anti-VEGF
therapy on the subset of Lucentis or Avastin patients treatment?
who need frequent injections every 4-6 weeks, I have not When I first started injecting years ago, I used to see the
found that the addition of PDT decreases the need for patients back within the first week. Over the past 4 years,
Lucentis injections. It’s important that when the combo I don’t see the patient back for a month or longer. They
trials are performed, all the controls are also performed are called to be sure all is well and they are instructed to
so we can determine if combo therapy really does call my office if their vision deteriorates or they experience
decrease the need for reinjection compared with pain after the first day.
treatment using prn injections alone. We routinely examine the patient on the next day and
then at one month & 3 months. Further follow-up
depends on the response achieved.
8 DOS Times - Vol. 13, No.1, July 2007
RVA: At 1st and 7th day after injection to rule out infection and RVA: improvement in visual acuity with reduction in the
RMG: uveitis. Next after 4 weeks to see the response. RMG: thickness & fluid on OCT.
SM: After 1 day, 1week, 4 weeks. Assess by symptoms, visual It’s a failure if even after 3 injection of avastin/lucentis or
PR: acuity, color photo and OCT. PDT+3 injections, FFA shows persistence leakage and
OCT demonstrates fluid.
PN: How you decide for re-treatment? On visual acuity, OCT If CNV does not respond at all to 3 injections, it is
RVA: or FFA? considered as failure.
RMG: I rely heavily on the OCT. I use the OCT qualitatively.
I don’t wait for a certain amount of fluid to accumulate, SM: Have you switched anti- VEGF agents in a single patient?
I will treat if there is any sign of fluid in the macula. Initially, PR: If yes, what is your experience?
I inject monthly until the macula is dry by OCT. I then see We have many patients who have switched from Macugen
the patient in follow-up monthly, and once I establish the PN: to Avastin and from Avastin to Lucentis. All the patients
patient’s fluid-free interval, I bring them back just before RVA: switching from Macugen to Avastin did better on Avastin.
I expect the fluid to re-accumulate. For example, if a RMG: We have not studied our experience switching patients
patient’s fluid-free interval is 2 months, then I’ll see them from Avastin to Lucentis. Overall, when we switched
every 7 weeks. If it’s 3 months, I’ll see them every patients from Avastin to Lucentis there was no difference;
10-11 weeks. Every patient is different. Another approach however, some patients did better on Lucentis and some
is to treat patients even when they are dry. For example, if patients did better on Avastin, but for the majority of
I treat a patient at baseline and 1 month, they may be dry at patients, there was no difference.
2 months. Even though they are dry, I might inject at We have switched from Lucentis to Avastin in a single
2 months and extend the next follow-up to 2.5 months. If patient. That was primarily to do with the cost factor of
they are dry at 2.5 months, then I inject again, and see them Lucentis which the patient could not afford a second
back at 3 months. This treat and extend method keeps the time.
macula dry until the length of the fluid-free interval is defined Yes. One patient. I used avastin after single injection of
by the increasing periods of extension, however, some lucentis as the patient could not afford further lucentis.
patients may receive unnecessary injections and may not After 3 avastin injections, both lesion and vision are stable.
need an injection for 6 months or longer. One one eyed patient had responded to avastin
We base our re-treatment decision mainly on visual acuity (2 injections) and was stable for 4 months but CNV
and OCT findings. In certain cases only do we advice a reoccurred. We gave Lucentis and CNV responded at
repeat FFA. 1 month but not as good as avastin. Now we are planning
All three. First of all is FFA to look for closure of the again for avastin in that same patient. Another one eyed
vessels. Second is the OCT to find out fluid. Persisting patient had received 3 injections of avastin but again showed
leakage on FFA and persistent fluid and non decreasing increased oedema on OCT and decreased visual acuity.
macular thickness are criteria for retreatment. Vision is After receiving 1 Lucentis there was excellent drying.
however less important.
When we give anti VEGF treatment, we prefer to give Success would be defined as
3 injections at 4-6 weeks interval irrespective of visual either stabilization or improvement
acuity, FFA or OCT features. It is only after 3 injections in visual acuity with reduction in
we follow the patient at 2-4 weeks interval. Retreatment
means patient has responded initially to the course of the thickness & fluid on OCT.
3 injections and CNV has reoccurred.
SM: How do you define success/failure? How many anti- SM: What is your concern regarding off-label use of avastin?
VEGF injections do you try before labeling as failure? Have you encountered any thromboembolic event?
PR: Failure is defined by visual acuity not by the number of PR: To date, we have not encountered any thromboembolic
injections. If a physician is treating the worse eye of a events that we attribute to Avastin or Lucentis. However,
patient and there’s no sign of improvement, the physician we would need to prospectively study at least 4000
and patient may decide that additional injections are not patients to reliably identify a 1-2% increased risk of
helping the patient’s quality of life and there is no point thromboembolic events compared with no treatment.
in continuing. However, if the treatment is in the better Remember, in the Blue Mountain Study, for the average
seeing eye, even if the vision doesn’t improve and even if patient with AMD, the annual thromboembolic rate was
it worsens, the patient’s quality of life would probably be 7.8%. I’m sure the rate in India is lower, but the point is
better if the treatments continue. Once again, every that we are looking for a 1-2% increase in a population
patient is different and the response to therapy will depend that already has a fairly high rate of thromboembolic
on the stage of the disease when the therapy was events. That’s why we need to study so many patients to
initiated. We make our clinical decisions based on the be sure about a safety signal.
patient’s unique situation. PN: Only concern about the off-label use of Avastin is related
PN: So far we have not felt the need to inject more than thrice to the medico-legal aspect. We feel that if the pre-injection
in any eye. So far all our cases have responded favourably. counselling is done well, even this should not be an issue.
There have been late recurrences but no real “failure” as We have not encountered any systemic complications
such. Success would be defined as either stabilization or with use of anti-VEGFs.
www.dosonline.org 9
RVA: I take written informed consent. I am not that much PN: patients. None of my prior Macugen patients would ever
RMG: concerned regarding off-label use. None of my patient go back to Macugen.
developed thromboembolic complication. RVA: Macugen has not really compared well with anti-VEGFs
We have not encountered any complication with avastin. RMG: in AMD cases. Its role would probably be limited to
One patient developed mild cerebrovascular accident patients with an unstable CVS condition, that too if a
after receiving Lucentis. definite risk is documented after anti-VEGF use (so far
we have not encountered any such event).
SM: If a patient with history of cerebrovascular accident/ Macugen has a role. But due to less clinical experience,
PR: myocardial infarction has occult CNV, what will be your I can’t make a candid statement.
treatment of choice? Do not have much experience.
PN: It doesn’t change my treatment of choice. I present the
RVA: options to the patient, and so far, it really hasn’t influenced SM: Should one try triple therapy at first go? PDT, Anti-
RMG: therapy. Even if there was a 1-2% increased risk, most PR: VEGF and IVTA.
patients are willing to take that small risk and would I would recommend that physicians start with
choose a 1-2% increased risk of a heart attack or stroke PN: monotherpy and identify those patients who really need
over a high probability of blindness or vision loss. RVA: frequent retreatment. Then, after discussing the
We would still go ahead with anti-VEGF treatment after RMG: possibility that combo therapy may result in a trade-off
a physician confirms that the CVS condition is stable at between visual acuity and the convenience of less frequent
present. treatment, they might go ahead and try combo therapy.
PDT+IVTA followed by repeat IVTA. But if vision/lesion I believe in keeping it as simple as possible and escalating
do not stabilizes or improves, I will discuss with the therapies as needed. My prediction is that current
patient for anti-VEGF treatment. combination therapies will not be as useful as everyone
In such a patient with good vision we will prefer suspects once we start using them on patients who need
observation. If with poor vision/recent progress of CNV, frequent retreatment with Lucentis or Avastin alone.
we will give avastin. What we really need is a therapy that can treat the
underlying disease, the dry AMD, and that’s what the
SM: If patient with similar systemic history has classic CNV, next 10 years will bring to our patients. Now, that’s the
PR: what will be your treatment of choice? kind of therapy that needs to be combined with Lucentis
Same as above. Remember, PDT was better than control, or Avastin.
PN: but PDT failed miserably against Lucentis for We are not in favour of such a triple therapy.
RVA: predominantly classic CNV in the ANCHOR trial. Right I do not believe in cocktail therapy. As results with
RMG: now, I see no first-line role for PDT unless a patient just 2 drugs are already there, I don’t see solid reasoning
can’t tolerate an injection. There’s also the theoretical behind triple therapy.
argument that PDT might be better in a vitrectomized Whenever indicated, PDT + Anti-VEGF give good
eye since the half-life of drug might be very short, but response. So why risk giving IVTA.
I would still give Avastin or Lucentis a try.
anti-VEGF would be the treatment of choice. Second session of PDT
PDT+IVTA followed by repeat PDT. Again if vision/lesion
do not stabilizes or improves, I will discuss with the
patient for anti-VEGF treatment.
We will prefer PDT + avastin (cant risk “life for vision”
knowing full well that avastin “does work”.)
SM: What is your opinion regarding role of macugen in Intravitreal bevacizumab
neovascular AMD?
Fundus photograph, FFA & OCT changes with PDT and subsequent
PR: Macugen has no role for neovascular AMD. They claim intravitreal bevacizumab injection in neovascular AMD in a 70-year-
Macugen is safer but they have no data, just a lot of old male. Pre-treatment (upper row), after two session of PDT (middle
theoretical speculation. And, if Macugen binds all the
major isoforms except VEGF121, why should it be safer? row) and after intravitreal bevacizumab injection (bottom row).
After all, if you read their own propaganda, VEGF 165 is (Courtesy: Prof. S P Garg)
the most prevalent isoform. In reality, they need to run a
4000+ patient study to make the safety claim, but that
won’t happen. The best evidence is from my Macugen
DOS Correspondent
Subrata Mandal MD
10 DOS Times - Vol. 13, No.1, July 2007
Wound Construction Cataract
Shalini Mohan MS, Sudarshan Khokhar MD, Anand Aggarwal MD, Anita Panda MD, FRCS
The trend in the cataract surgery has been towards smaller Depending on the Site
incision, moving from superior scleral incision to temporal
clear corneal incision, in an attempt to reduce post operative Incision can be of following types on the basis of the site.
astigmatism.
• Temporal
Anatomy of Limbus • Superior
• Oblique: superotemporal / inferotemporal
Surgical limbus can be divided into two zones by three lines • In correspondence to axis of greater curvature.
(Figure 1)1
The site of incision depends on induced astigmatism and
Anterior limbal border: corresponds to termination of Bowman’s ergonomics of the surgery.
membrane and is marked externally by insertion of Tenon’s capsule
and conjunctiva that forms a prominent ridge. The temporal approach provides the surgeon easiest access to the
surgical zone because it is not obstructed by the orbital edge of
Middle limbal border: when conjunctiva and Tenon’s capsule is frontal bone and minimizes the effect of Bell’s phenomenon. The
dissected there is a bluish zone visible followed by a white zone of horizontal meridian of cornea is more than the vertical meridian.
sclera. The junction between these two is known as middle limbal Therefore, the distance from periphery to visual axis is longer in
border. This is the termination of Descemet’s membrane and this position and it is also less flattening. More over there is no
overlies the Schwalbe’s line. role of bridle suture in such cases. There is also marked increase in
the red reflex because the iris is perpendicular to the light of
Posterior limbal border: lies over the scleral spur and can be seen microscope. It also facilitates drainage of fluid through lateral
only with sclerotic scatter. It is 1 mm behind the middle limbal canthus and thus prevents fluid accumulation. Therefore, the most
border.
Astigmatic Neutral Funnel
The concept has been derived from two important mathematical
equations:
• Surgically induced astigmatism (SIA) α length of incision2
• SIA α1/distance of incision from corneal centre
Therefore, it was found that incision of 3-3.5 mm at the limbus Figure 1. Surgical limbus
results in minimal astigmatism of 0.25 – 0.50 D and it can be
considered astigmatically neutral for all practical purposes. The
funnel’s base is at the limbus and as it moves away it widens
(Figure2). The incision which is made within this funnel is
astigmatically neutral.
Self Sealing Incision
A self sealing incision is characterized by a corneal valve and square
incisions. When IOP of the eye rises it causes corneal valve to
close against the pressure of aqueous so that it is pushed up
against the dome of cornea. The smoother and larger is corneal
lip, better is the sealing action. A 4 mm width with 1.75 mm length
is sufficient to create a self sealing incision3.
Classification of Small Incision
Small incision means any incision having a size of 5mm or less.
These can be classified into following categories:
• Site Figure 2. Astigmatic neutral funnel
• Position
• Size
• Shape
Dr. Rajendra Prasad Centre for Ophthalmic Sciences,
All India Institute of Medical Sciences,
New Delhi-110029
www.dosonline.org 13
popular incision these days is temporal approach as it also produces
excellent results in terms of astigmatism, both immediate and
long term3.
The superior approach was popular few years ago but now it is
preferred only in the cases of the sclero corneal tunnel. It can be
used to reduce with the rule astigmatism. It is found that induced
astigmatism from temporal versus superior incisions is 0.6D versus
0.9D3. This is due to effect of flattening which is less in the temporal
approach than the superior.
The oblique incisions are made for better ergonomics but only
provide partial benefit of temporal incisions.
The incisions on the steepest meridian (on-axis) can be made to Figure 3. Phacoemulcification in operated Radial Keratotomy eye.
reduce mild pre operative astigmatism of 1 D or less as it causes Ballooning of conjunctiva is seen.
flattening of the meridian in which incision is given with increase
in curvature of the opposite meridian2. A latest study done by • A shallow anterior chamber is extremely rare
making ‘on axis’ incision, in various locations to correct
preoperative astigmatism showed that nasal incision increased • Less chances of formation of peripheral anterior synechia,
preoperative cylinder from 1.13 D to 1.83 D 6 months after because the internal aspect of the wound is further forward
surgery.4 than the cornea /scleral and well away from iris.
Depending on the Position • Less chances of expulsive choroidal hemorrhage
Depending on the position incision can be of following types: • In cases of expulsive choroidal hemorrhage, merely taking
the instruments out results into the immediate closure of the
• Corneal eye.
• Limbal (near corneal) • Similarly in the patients with cardiac / respiratory arrest the
instruments can be withdrawn followed by resuscitation.
• Scleral
• Sclero-corneal Disadvantages
For the obvious reasons the astigmatism decreases as the incision There is poor wound stability and therefore it can lead to leakage
moves from the clear cornea to the sclera. causing:
Corneal Incisions • Hypotony
The incisions are known as clear corneal when the anterior limit is • Endophthalmitis
positioned anterior to the limbal vascular arches. • Relatively high astigmatism
• Early high rise of IOP
Advantages • Slower healing
• The surgery can be performed under topical anaesthesia Contraindications
• Obviates the need for manipulation of conjunctiva and • Preoperative radial keratotomy where the incisions extend as
therefore reduced scarring which offers futures advantages far as limbus (Figure 3)
of filtering surgery, if required
• Peripheral corneal degenerations
• Esthetically satisfactory result Limbal Incisions
• Facilitates intraoperative visibility as the tunnel is shorter and When the external incision is made 0.5 mm posterior to the external
hence less intra operative stria formation arcades then it is known as limbal incision.
• Total surgical time is less
• Fewer instruments are required
• There is no bleeding except in cases of vascularised corneas. Advantages
Therefore, there is lower incidence of hyphemas and so no Besides the advantages of the clear corneal incisions they have
contraindication to anticoagulants additional benefits like:
• Decreased incidence of iris prolapse • They induce less astigmatism as they are away from the visual
• The eye is protected from epithelial in growth axis
• Heal more rapidly
14 DOS Times - Vol. 13, No.1, July 2007
• Cause less discomfort
• Offer greater resistance to pressure with respect to clear
corneal incisions.5,6
Disadvantages
• The main disadvantage is ballooning of conjunctiva (Figure 3)
which can lead to poor visibility during surgery.
• The bleeding from the limbal vessels can track into corneal
tunnel and can cause staining of the tunnel which can persist
postoperatively.
• Increased risk of sub conjunctival hemorrhage, which can be
of prime psychological concern for the patient.
Relative Contraindications
The indications of the limbal incision are gradually expanding but
in certain situations corneal incisions are to be preferred over limbal
incisions. These are patients with increased tendency for bleeding3:
• Diabetic patients Figure 6a. Stab (uniplanar) incision
• Patients on anticoagulant therapy
• Patients with blood dyscrasias IOLs. These incisions have got better sealing properties. Thses are
made 1.5-2.0 mm posterior to the limbus (Figure 4). They can be
• Patients with history of alcohol abuse sutureless if a tunnel is created with an internal corneal lip.
Otherwise the incision can be closed with a single 10-0
Sclero Corneal Incision monofilament nylon infinity suture.
These incisions are made electively when a larger incision of The scleral flap incision has three dimensions (Figure 5):
5 mm or more is needed to implant an IOL. These are sometimes
also used in pediatric cataract surgery cases for implanting rigid • Depth
• Width
• Length
Depth
The sclera is 0.6 mm thick, 2 mm posterior to limbus. So the
incision depth ranges from 0.1 mm to 0.5mm. Flap depth can be
determined accurately with a guarded calibrated diamond knife.
Width
Figure 4. Scleral incision The distance between the external groove and the internal entry
into the anterior chamber is the width of the incision (Figure5).
For production of an astigmatically neutral incision the external
incision should be as far as possible to minimize the effect of the
suture. More over wider the flap, lesser is the astigmatism as it
provides the pillar which supports the existing shape of the eye.
But one can not move too far off as it is limited by the amount of
the bleeding and difficult manipulation in the anterior chamber.
Advantages
• Minimal astigmatism induction
• Better resistance to both internal and external pressure.
Disadvantages
Figure 5. Scleral flap incision • The conjunctival aperture must be large. Otherwise there is a
need to put in the superior rectus bridle suture or clear corneal
www.dosonline.org 15
Creation of side port 1.4mm MVR blade. corneal flap which is more resistant when caught with forceps
or when sutured.
• Triplanar incision (Figure 8): after making a groove, blade is
made to travel parallel in cornea and then dips down into the
anterior chamber.
Figure 6b. Stab incision being made with MVR knife. • The hinged incision (Figure 9): was proposed by Langerman.8
It is known that when properly performed the corneal
traction suture. incisions do not leak when ever pressure is applied to the dome
of cornea. But it does leak when the pressure is applied to the
• Diathermy is necessary posterior lip of the incision7. This incision is characterized by
a hinge perpendicular to the corneal surface and 0.75 mm
• Greater time is required for wound construction deep. The corneal tunnel is constructed at a depth of about
500 µm, a depth superior than the hinge. This consists of
• Greater discomfort for the patient if surgery is being marking of a groove that is deeper than the plane of the
performed under topical anesthesia. In such cases, a tunnel. The hinge physically separates the floor of the tunnel
subconjunctival anesthesia is usually required. from the posterior wall of the groove. In this way when
pressure is applied onto the posterior lip of the incision, the
• The manipulation of the instruments inside the eye is difficult groove and the external part of the tunnel open but the internal
because of frequent corneal distortion. part of the tunnel seals. There may be small amount of leakage
in the initial post operative period but this may cause the
Depending on the Shape inferior part of the corneal lip to become flaccid as it is thinner
than the superior part, therefore it seals the incision.9
When examined in longitudinal section, the incisions can be of
following types: Hayashi et al also did a study to correlate between incision sizes
and change in the corneal shape in suture less surgery using corneal
• Single plane, one step stab incision (Figure 6a)- it was topography. They found that 3.2 mm incision did not induce any
proposed by Fine7 and is prototype of a clear corneal incision. significant corneal shape changes in comparison to 4 mm and 5mm
The blade is driven into the eye upto 2 mm (Figure 6b). Then incisions.10
the blade is dipped to nick Descemet’s membrane and the
blade is driven upto its hub. The shape of the sclero corneal incisions can also be classified in
terms of the initial cut. 7 (Figure 10)
• The Biplanar (Figure 7) was introduced by Williamson2,7 and
is characterized by a groove of 300-400 µm perpendicular to • Parallel to limbus – convex
the corneal surface and is arc shaped. The tunnel starts from
the deepest part of the groove. This shape creates a thicker • Antiparallel- frown incision
• Straight
• Arrow like- chevron incision
Figure 7. Biplanar (grooved) incision Figure 8. Triplanar incision
16 DOS Times - Vol. 13, No.1, July 2007
upon the IOL to be implanted. The insertion with forceps or an
injector tends to widen the incision by 10%7. The recently
developed rollable IOLs can be implanted through an incision size
of 1.1 mm. The studies clearly demonstrate that increase in length
of incision increases the degree of SIA. In cases of sclero corneal
incision, the size of the astigmatically neutral incision can be upto
4.5 mm & in cases operated through corneal or near corneal
incisions the size is 4 mm.
In an experimental study it was found that microincision coaxial
phacoemulsification (2.2mm size) and standard coaxial
phacoemulsification (2.75mm) induce less wound stress and
alteration of wound morphology leading to less wound leakage
than microincision bimanual phacoemulsification (1.2mm)11.
Surgical Technique
Construction of Scleral Tunnel Incision
Wound Architecture:
Figure 9. Hinged incision The important step in this procedure is creation of a tunnel which
is joined by (Figure 11)
• “J’ shaped
• External incision: it is the scleral groove and the types have
• Trapezoid shaped already been described above.
When the incision is made in the astigmatically neutral funnel • Internal incision: the entry into the eye
then with same chord length and with equal distance from the
limbus, a convex incision will extend slightly outside the funnel Surgical Steps
followed by straight and then the concave incision having the least
part outside the funnel (Figure 2) . Therefore, astigmatism will • Conjunctival flap is made precisely as the width of the scleral
also be maximum with convex incision. Sagging of the incision tunnel followed by vertical releasing incisions in the
leading to wound gape is also maximum with convex incision. conjunctiva and Tenon’s capsule extending approximately 5
The last of the above two incisions have been made to reduce mm.
astigmatism as they remain entirely inside the funnel but are not
very popular. • Mild bipolar cautery is performed. However, the larger vessels
are to be directly and adequately cauterized so that the tunnel
Depending on Size (Length) remains dry during the entire procedure.
The size of the incision can vary from 1 mm to 6.5 mm depending • Following this a caliper is taken and a 5mm mark is given 1 -
2mm behind the limbus.
• The sclera is cut perpendicularly which should be atleast 50 %
Figure 10a. Scleral Incisions: parallel Figure 10b. Scleral Incisions: Straight
Figure 10c. Scleral Incisions: Antiparallel Figure 10d. Scleral Incisions: Cheveron
www.dosonline.org 17
Initial Curvilinear Incision Scleral tunnel central with Side pocket creation of
crescent blade scleral tunnel
Figure 11. Scleral incision construction
scleral depth (Figure 11) so that the surgeon can look down membrane is there. It is non self sealing and requires
the groove and pick the depth within the sclera and dissect other associated manuever Suturing lite for sealing to take
the scleral tunnel.9 A crescent knife is used to dissect the tunnel. place.
The leading edge of the knife should be down while cutting
anteriorly or sideways (Figure 11). Construction of Clear Corneal Incision
• Now, viscoelastic is injected into the anterior chamber after A fine Thornton 13 mm fixation ring can be used to allow the
making a side port. This results in a very stiff and stable anterior globe stabilization and manipulations without creating conjunctival
chamber. tears, sub conjunctival hemorrhage or corneal abrasion. This is
especially true for cases taken up under topical anesthesia. A
• A 3.2 mm keratome is brought into the tunnel and at the sideport is created with a MVR knife. After staining the anterior
anterior edge of the vascular arcade; it is depressed lightly capsule with trypan blue, the anterior chamber is pressurized with
resulting in a dimple formation on the anterior corneal surface. a viscoelastic. Now, a 300 µm groove is placed at the anterior edge
The dimple is frequently outlined by a semi circular light of the vascular arcade. Then, an incision is made by depressing the
reflex with the tip of keratome at the centre. posterior edge of the groove with a 3.2 mm or 2.75 mm keratome
flattening the blade against the surface of the eye (Figure 12).
• Now, the keratome is advanced horizontally parallel to the Now, the blade is moved in the plane of the cornea until the
iris which results in a linear horizontal cut through the shoulders which are 2 mm posterior to the point of the knife
Descemet’s membrane into the anterior chamber. A straight touch the external edge of the incision and following this, a dimpled
cut in the descemet’s membrane is necessary for the correct down technique as described previously, is utilized to initiate the
architecture of the incision. cut through the Descemet’s membrane. After phacoemulsification
and cortical clean up, the incision in the Descemet’s membrane is
The important thing to note is that forceps is used to elevate the widened with a blunt tipped keratome depending upon the IOL to
tunnel roof while placing the keratome inside the tunnel but be implanted (Figure 13).
counter traction is placed on the posterior lip of the groove rather
than anterior lip during cutting of the Descemet’s membrane with After the anterior chamber is pressurized by BSS through the side
a keratome. The use of chilled Balanced Salt Solution (BSS) port, the lips of the wound is tested by applying pressure with a
maximizes cooling of the phaco tip, thus minimizing tunnel sponge against the posterior lip of the wound. If the incision leaks,
shrinkage and consequent irregular astigmatism.
Internal incision: can be of two varieties –
• Corneal lip incisions – it is created by a 3 step procedure.
Here an external incision is made followed by creation of a
tunnel through the sclera which enters about 2 mm into the
clear cornea. This is followed by entry into the anterior
chamber. This creates the corneal flap/lip which acts as a self
sealing incision. The wound seals when the eye is closed under
normal IOP by injecting saline into the anterior chamber. The
posterior corneal lip is pushed up through pressure of the
fluid into the anterior chamber and closes the wound.
• Non corneal lip incisions – It is directly beveled into the anterior Figure 12. Clear corneal temporal incision being made
chamber from external incision in a two step fashion. The
anterior chamber entry is just anterior to the Schwalbe’s
line so that only a small ledge of the descemet’s
18 DOS Times - Vol. 13, No.1, July 2007
5.2mm Keratome for wound enlargement for Premature entry: This common complication especially in
PMMA IOL insertion. learning curve, can lead to intra operative iris prolapse besides
making the incision non self-sealing and shallowing of anterior
chamber. The options available to deal with this complication are
following:-
• If iris prolapses, it should be reposited back and another tunnel
made underneath the original incision, this time making sure
that the internal entry is more than the original width. The
original incision gets sealed by the roof of the new tunnel
when the pressure is exerted from the fluid entering from the
phaco probe.
Figure 13. Enlargement of incision for implantation of rigid IOL. • Alternately, the iris is reposited back, the wound secured with
one 10-0 nylon suture, and the surgeon should shift to another
a single 10-0 nylon monofilament suture is placed. Following position (if temporal originally, then shifting to a superior
completion of the phacoemulsification procedure, stromal position is appropriate with fresh incision construction).
hydration of the clear corneal incision can be performed in order
to seal the incision. A calibrated angled diamond knife or a disc knife is also available
for proper tunnel construction. The surgeon should enter the
The rationale for grooved clear corneal incision was to make a anterior chamber after injecting sufficient viscoelastic and the blade
thicker external edge to the roof of the tunnel and less likelihood should be angled upwards while making the tunnel.
of tearing or cheese wiring. Langerman’s single hinged incision
had minimal differences in surgically induced astigmatism from A long entry may result into compromised visualization due to
grooved incision.8 striae formation in the cornea and make subsequent steps difficult.
Complications Tearing of roof of the tunnel can result especially at the edges because
of discrepancy in the size of the incision and phaco handpiece
Intra Operative (Figure 15).
Complications can be seen in all types of incisions but clear corneal Tearing of the internal lip can also occur causing the incision to
incisions by the nature of their architecture and location have some lose its self sealing character or rarely a small Descemet’s membrane
unique complications associated with them. detachment or scrolling of descemet membrane in anterior edge
of the incision.
Ballooning of conjunctiva (Figure 3): This complication may be
seen if one incidentally incises the conjunctiva. This may hamper Incisional burns leading to incision thermal contraction can
the subsequent visualization due to fluid accumulation and develop in clear corneal incisions. They cause compromised self
seriously increases the rate of intraoperative complications sealability, corneal edema and severe induced astigmatism. A study
including posterior capsular rent. This can be relieved by making done on 76,581 procedures found incidence of wound burn as
multiple nicks in conjunctiva to drain the fluid. 0.98/1000 procedures. Twenty eight percent occurred during early
sculpting, and 71% occurred during fragment removal.12
Staining of tunnel: Use of crescent blade to make corneal tunnel
can cause blood to track down the incision causing staining of A extremly narrow tunnel may obstruct the irrigation portion of
tunnel (Figure-15). the phaco sleeve and compromises inflow which can lead to corneal
burn. This is especially true in cases operated via Micro incision
cataract surgery (MICS). This complication has now been reduced
through various phaco power modulations now available, with
the newer generation phaco machines. Customizable power
Figure 14. Blood staining of the tunnel. Figure 15. Tear of anterior lip due to thin anterior tunnel.
www.dosonline.org 19
Table 1. Studies comparing Astigmatism in scleral tunnel superior and clear corneal A RPC study evaluated paired 3.2 mm
temporal approach phacoemulsification opposite clear corneal incisions made in the
steep axis in one group with single clear
Author Incision Astigmatism Astigmatism Duration corneal incisions in the other group. Mean
size (Superior (Temporal of study SIA was 1.66 +/- 0.50 D and 0.85 +/- 0.75 D
approach) approach) in Group 1 and Group 2, respectively (P =
.00). They concluded that paired opposite
Lyhne 200119 4.0mm 0.61D 0.41D 12 months clear corneal incisions were predictable and
Roman et al 199820 4.0mm 0.69D 0.69D 12 months effective in providing an enhanced effect
Oshima et al199721 3.0mm 0.65D 0.56D 3 months for correcting preexisting corneal
Roman et al199722 4.0mm 0.98D 0.58D 1 months astigmatism in cataract surgery18.
Table 2. Studies comparing Astigmatism in clear corneal superior and clear corneal Table 1 shows various studies comparing
temporal approach phacoemulsification superior with temporal incision. The range
is 0.41D – 0.69 D for temporal clear corneal
Author Incision Astigmatism Astigmatism Follow up in comparison to 0.61D- 0.98D in superior
size (Superior (Temporal scleral incision19,20,21,22 .
approach) approach)
The effect of 2.75 mm clear corneal incision
Marek et al 200624 2.8mm 0.96D 0.54D 3 months on SIA was also reported. The study
Roman et al 199820 4.0mm 1.52D 0.69D 12 months revealed that there was little difference in
Simsek et al199825 — 1.44D 0.62D 3 months the SIA of 2.75 mm incision regardless of
the incision site.23
modulation with microburst and hyperpulse technology13 further Table 220,24,25 shows the range of
reduces wound temperature during bimanual sleeveless astigmatism induced in various studies. Similarly sized incisions
phacoemulsification. Studies done to compare the thermal effect larger than 2.75 mm, when compared in regards to wound location
of the three recent machines Alcon Legacy AdvanTec, Bausch & (temporal versus superior clear corneal incision) have
Lomb Millennium, and AMO Sovereign WhiteStar showed that demonstrated more flattening in the superior axis. The oblique
under a variety of power, load, and duty-cycle settings, the supero lateral clear corneal incision has also demonstrated more
Millennium and the Sovereign WhiteStar, operating in both pulse flattening with the passage of time. That’s why the current trend is
and continuous modes, generated higher peak temperatures than moving towards temporal approach phacoemulsification when
the Legacy AdvanTec.14 astigmatic neutral incision is desired.
Recently Aqualase emulsification technology is fast gaining Now it is being emphasized that corneal topography guided
popularity especially in cases of refractive lens exchange. This incisions can yield better visual acuity by reducing the pre-existing
technology is supposed to cause minimal heat generation as astigmatism and inducing less corneal aberrations than
microfluid pulses are being employed for nuclear disassembly in conventional temporal corneal tunnel phacoemulsification.26
place of ultrasound.
A study done to compare the astigmatism and high order
Post Operative Complications aberrations of the cornea after microincision versus small incision
cataract surgery found that Microincision cataract surgery
Post operative hypotony may be seen in cases of poor sealability of generates statistically significantly less corneal astigmatism and
incision. better optical quality of the cornea compared with small incision
cataract surgery. However, microincision cataract surgery showed
Wound leak and iris prolapse can occur in infrequent case especially no significant advantage in reducing corneal high order
if the wound size is more than 3.5 mm width. aberrations27. Similarly, corneal and sclero corneal incisions can
also be considered equivalent in terms of inducing higher order
Increased risk of endophthalmitis has been noted in a large meta aberrations.
analysis15 in case operated via clear corneal incision of more than
4 mm size in comparison to sclero corneal incision. Conclusions
Clinical Course and Outcome It is a common dictum that ‘well begun is half the work done’. The
incision used for cataract surgery has to serve 3 purposes- the
Comparison of temporal clear corneal incision size of 3.5 mm, ease of performance of phacoemulsification, minimum
4 mm and 5 mm found a mean induced astigmatism of 0.37D, astigmatism induction, safety and self sealability of the incision.
0.56 D and 0.70 D respectively after 6 months.16 Smaller size of incision and proper wound construction has
transformed cataract surgery. With clear corneal incisions coming
A study done to evaluate the surgically induced astigmatism in the into vogue, the surgery can be done under topical anesthesia with
eyes operated via temporal clear corneal incision versus ‘on axis’ relative astigmatic neutrality and almost instant visual
corneal incision showed that the surgical induced astigmatism (SIA) rehabilitation. With increasing expectations of patients following
was less in eyes operated via clear corneal temporal incision. cataract surgery, it is becoming more and more imperative on part
However, the drawback of the study was a relatively short duration of the surgeon, not only to give good best corrected visual acuity
of follow up before astigmatism analysis (done at 7 weeks).17
20 DOS Times - Vol. 13, No.1, July 2007
but also fairly good uncorrected acuity. For the attainment of the 14. Olson MD, Miller KM. In-air thermal imaging comparison of
second goal, proper surgical incisions are now being increasingly Legacy AdvanTec, Millennium, and Sovereign WhiteStar
combined either with limbal relaxing incisions or phaco being phacoemulsification systems. J Cataract Refract Surg
performed on the steep meridian to correct pre existing corneal 2005;31:1640-7.
astigmatism, or through the use of opposite clear corneal incisions
at the time of phacoemulsification.18 No doubt, these incisions 15. Taban M, Behrens A, Newcomb RL, Nobe MY, Saedi G, Sweet TM,
have clearly revolutionized the outcomes and acceptance of cataract McDonnell PJ. Acute endophthalimitis following cataract surgery-
surgery. Taking clues from these incisions, the same incisions are A systematic review of literature. Arch Ophthalmol 2005;
also being increasingly used for undertaking posterior lamellar 123(5): 613-20.
corneal procedures like deep lamellar endothelial keratoplasty
(DLEK). 16. Kohnen T, Dick B, Jacobi KW. Comparison of the induced
astigmatism after temporal clear corneal tunnel incisions of different
References sizes. J Cataract Refract Surg 1995;21:417-24.
1. Kasner D. Important aspect of surgical anatomy of the limbal area. 17. Borasio E, Mehta JS, Maurino V. Surgically induced astigmatism
In: the new report on cataract surgery. Welsh RC, Welsh J eds. after phacoemulsification in eyes with mild to moderate corneal
Miami, Miami educational press, 1971, pp 106-107. astigmatism: temporal versus on-axis clear corneal incisions.
J Cataract Refract Surg 2006 ;32:565-72.
2. Tadros A, Habib M, Tejwani D, Von Lany H, Thomas P. Opposite
clear corneal incisions on the steep meridian in phacoemulsification: 18. Khokhar S, Lohiya P, Murugiesan V, Panda A. Corneal astigmatism
early effects on the cornea. J Cataract Refract Surg 2004;30:414-7. correction with opposite clear corneal incisions or single clear
corneal incision: comparative analysis. J Cataract Refract Surg.
3. Savini G, Zanini M, Buratto L. Incision. In: Phacoemulsifications, 2006;32:1432-7.
Principles and techniques. Buratto L, Werner L, Zanini M, Apple D,
eds. II edition, Ch 3, pp69-82. 19. Lyhne N, Krogsager J, Corydon L, Kjeldgaard M.One year follow-
up of astigmatism after 4.0 mm temporal clear corneal and superior
4. Altan-Yaycioglu R, Akova YA, Akca S, Gur S, Oktem C. Effect on scleral incisions. J Cataract Refract Surg. 2000 Jan;26(1):83-7.
astigmatism of the location of clear corneal incision in
phacoemulsification. J Refract Surg. 2007;23:515-8. 20. Roman SJ, Auclin FX, Chong-Sit DA, Ullern MM . Surgically
induced astigmatism with superior and temporal incisions in cases
5. Ernest PH, Neuhann T. Posterior limbal incision. J Cataract Refract of with-the-rule preoperative astigmatism. J Cataract Refract Surg.
Surg 1996;22:78-84. 1998 Dec;24(12):1636-41
6. Kapoor S. Incisions. In: Agarwal S, Agarwal A, Sachdev MS, Mehta 21. Oshima Y, Tsujikawa K, Oh A, Harino S Comparative study of
K, Fine HI, Agarwal A eds Phacoemulsification, Laser Cataract intraocular lens implantation through 3.0 mm temporal clear
surgery and foldable IOLs, Jaypee Brothers, New Delhi;1998: corneal and superior scleral tunnel self-sealing incisions. J Cataract
Ch9,pp 67-80. Refract Surg. 1997 Apr;23(3):347-53
7. Fine IH. Clear corneal incisions. Int Ophthalmol Clin 22. Roman S, Givort G, Ullern M. Choice of the site of incision for
1994;34:59-72. cataract surgery without suture according to preoperative
astigmatism. J Fr Ophtalmol. 1997;20(9):673-9.
8. Langerman DW. Architectural design of a self-sealing corneal
tunnel, single-hinge incision. J Cataract Refract Surg 1994;20:84-8. 23. Giansanti F, Rapizzi E, Virgili G, Mencucci R, Bini A, Vannozzi L,
Menchini U. Clear corneal incision of 2.75 mm for cataract surgery
9. Jaffe NS, Jaffe MS, Jaffe GF, eds. Cataract surgery and its induces little change of astigmatism in eyes with low preoperative
complications. Mosby Singapore, 1997; ch 5, pp72-76. corneal cylinder. Eur J Ophthalmol. 2006;16:385-93.
10. Hayashi K, Hayashi H, Nakao F, Hayashi F. The correlation between 24. Marek R, Klus A, Pawlik R. Comparison of surgically induced
incision size and corneal shape changes in sutureless cataract astigmatism of temporal versus superior clear corneal incisions. Klin
surgery. Ophthalmology 1995;102:550-6. Oczna. 2006;108(10-12):392-6.
11. Berdahl JP, DeStafeno JJ, Kim T. Corneal wound architecture and 25. Simsek S, Yasar T, Demirok A, Cinal A, Yilmaz OF. Effect of superior
integrity after phacoemulsification evaluation of coaxial, and temporal clear corneal incisions on astigmatism after sutureless
microincision coaxial, and microincision bimanual techniques. phacoemulsification. J Cataract Refract Surg. 1998 Apr;
J Cataract Refract Surg 2007;33:510-5. 24(4):515-8.
12. Bradley MJ, Olson RJ. A survey about phacoemulsification incision 26. Jiang Y, Le Q, Yang J, Lu Y. Changes in corneal astigmatism and
thermal contraction incidence and causal relationships. high order aberrations after clear corneal tunnel
Am J Ophthalmol 2006 ;141:222-4. phacoemulsification guided by corneal topography. J Refract Surg.
2006 Nov;22(9 Suppl):S1083-8.
13. Braga-Mele R. Thermal effect of microburst and hyperpulse settings
during sleeveless bimanual phacoemulsification with advanced power 27. Yao K, Tang X, Ye P. Corneal astigmatism, higher order aberrations,
modulations. J Cataract Refract Surg 2006;32:639-42. and optical quality after cataract surgery: microincision versus small
incision. J Refract Surg. 2006 Nov;22(9 Suppl):S1079-82.
Author
Sudarshan Khokhar MD
www.dosonline.org 21
Capsulorhexis Cataract
Tanuj Dada MD, Harinder S. Sethi MD, FRCS, Munish Dhawan MD,
Vivek Dave MBBS, Kiran G. Krishnan MBBS, MD
The capsulorhexis or continuous curvilinear capsulotomy • Tip of a 26 G needle
(CCC) is perhaps the most important development in the era
of modern day cataract surgery. It has the following advantages1: • MVR knife
• Allows a safe in the bag phacoemulsification. • Tip of steel/diamond keratome during wntry into anterior
chamber.
• Ensures proper placement and centration of the IOL
• Pointed tip of capsulorhexis forceps
• Prevents haptics from getting displaced out of the capsular
bag. • Sharp chopper tip
• Renders the capsular bag more resistant to tearing • Vitrectomy probe facing port facing posteriorly
• Allows placement of IOL over it in the event of posterior Surgical Techniques
capsule rupture
Needle Capsulorhexis
• Intraoperative stress on the zonules is minimal and is
distributed evenly Using a bent needle of 24 G to 26 G, a perforation is made in the
centre of the anterior capsule. By extending this with the sharp
• Easier cortical aspiration as no capsular tags edge of the needle, a horizontal incision is made. The tip of the
needle is now used to redirect the tear in a clock-wise direction.
Prerequisites The circular tear is started by lifting and pushing or pulling the
central part of anterior capsule according to the direction in which
A deep anterior chamber, a flat anterior lenticular curvature, and surgeon wishes to start. This creates a flap that can be easily turned
a optimal visibility are important pre-requisites for starting the on it, engaged with the needle tip and torn in a circular manner by
capsulorhexis. Putting methyl cellulose over the cornea, improves applying the tear vectors accordingly. If the tear starts to extend
visibility during the procedure and prevents drying of the cornea peripherally, it is usually the result of positive vitreous pressure
during the entire procedure. The anterior chamber can be formed which can be countered by reinflating the anterior chamber with
by the use of viscoelastic agents, air or irrigation fluid. It always viscoelastic. A light touch is needed, because if one presses too
better to stain the anterior capsule with trypan blue before starting hard on the flap, it creates a corresponding increase in vitreous
the capsulorhexis2. The dye is injected under air and washed after pressure, which forces the tear outward. As the flap progresses,
a 10 second interval. large amounts of capsular folds will present and must be pushed
out of the way, so that one can visualize the exact point at which to
Instruments place the tip of the needle. When completing the capsulorhexis,
one should overlap the tear in such a manner that the last part of
Cystitomes, bent needles or forceps, can all be used effectively. the tear joins the first part from the outside towards the centre,
The initial tear can be made with the tip of the MVR / V Lance thus resulting in a continuous edge (Figure 1). If the overlap is
knife or the 2.75-3.2 mm keratome and rest of the procedure created from the centre towards the periphery, it will result in a
completed with just a routine McPherson forceps. Ultrasonic or small triangular flap, with a tendency to tear towards the equator
thermal devices do not offer any additional advantage and are not of the lens or beyond.
usually required. The Plasma (FUGO) blade is helpful in fibrotic
anterior capsules. If the surgeon uses a bent 26-gauge needle mounted on a syringe,
the syringe can be filled with 2% HPMC. This is injected into the
Initiation of the tear anterior chamber while the capsulorhexis is being performed
without having to withdraw the needle and inject HPMC through
Anterior chamber is inflated with an ophthalmic viscoelastic the side port.
device. Using a bent tipped needle, capsulorhexis is started by
making a small cut at the centre of lens, pulling directly toward The best control of the tear as it progresses is achieved by grasping
the 12 o clock position and curving toward left. With the initial the developing capsular flap, with the desired instrument close to
cuts made centrally, radial stress vectors across the anterior capsule the point from where the capsule is tearing at that time. The
are interrupted, resulting in fewer tendencies for the tear to extend direction of the tear can be controlled by the position of the
towards the equator. It is always easier to spiral the initial tear out instrument. Placing the tip of the instrument a little peripheral to
to enlarge a capsulotomy, than it is to pull a peripheral tear back the advancing tear, will direct it outwards. Placing it a bit central
towards the centre. The tear can be initiated by the following to the line of the tear will direct it towards the centre. A smaller
methods3: diameter capsulorrhexis is easier to control than a larger one. For
most patients, a capsulorrhexis diameter measuring 0.5 mm to
Dr. Rajendra Prasad Centre for Ophthalmic Sciences,
All India Institute of Medical Sciences,
New Delhi-110029
www.dosonline.org 23
Figure 1. Needle capsulorhexis
Figure 2. Forceps capsulorhexis
1.0 mm smaller than the IOL’s optic diameter is preferred. capsulorhexis Using the forceps requires a larger opening into the
The IOL generally remains well centered postoperatively in this anterior chamber as compared to a bent needle, and additional
situation. However, in eyes that have weakened zonules or have an viscoelastic is usually necessary. A cohesive viscoelastic like sodium
excessively hardened nucleus, uveitic cataract surgery and piggy hyaluronate can be used for this purpose. If healon 5 is used, it
back IOL implantation, a capsulorrhexis diameter that is 0.5 mm applies excess pressure on the anterior capsule and this can lead to
to 1.0 mm larger than the optic is preferred. It is important to a smaller capsulorhexis than desired. During a forceps
avoid making a capsulorrhexis equal to the optic diameter because capsulorhexis, the surgeon should watch the proximal end of the
the IOL can “pea-pod” off center as the capsulorrhexis and capsular forceps as the iris may be caught in it.
bag contract postoperatively. Tear patterns may vary, and it is
possible to progress in a clockwise or counter clockwise manner. Bimanual Capsulorhexis
There are cases, however, in whom no form of capsulorhexis may It is cost effective to use 2% hydroxypropyl methylcellulose (HPMC)
be achieved. These include capsules that are heavily fibrosed and for the capsulorhexis. The problem with using this dispersive
shrunken, as in certain congenital, secondary and traumatic viscoelastic material while making a capsulorhexis with a forceps
cataracts. In these patients, a continuous, curvilinear opening may is that it is not retained well in the anterior chamber. To overcome
still be achieved by using a capsule scissors to cut through the this problem, the authors have described a technique in which
fibrosed part of the anterior capsule. In the non-fibrosed area, the viscoelastic material is continuously injected through the side port
smooth edged border of the capsulorhexis is achieved by the usual with one hand while the other hand performs the capsulorhexis.
methods. The cannula of the viscoelastic syringe is put through the side port
and viscoelastic material is continuously injected to maintain a
The surgeon should watch carefully if the tear is extending to the deep anterior chamber and flatten the curvature of the anterior
periphery as the tear may have already entered the area of zonular lens surface, while the forceps is being moved to perform the
attachments. In such a situation a Vannas scissors may be used to capsulorhexis (Figure 3). The cannula put through the side port
cut the zonular attachments and then one can continue with the also helps in stabilizing the globe while the capsulorhexis is
tear. performed.
Forceps Capsulorhexis The capsulorhexis can be initiated by giving the initial nick with
the MVR knife or the tip of the 3.2 mm Keratome in the centre of
A Kraff-Utrata forceps can be used to perform capsulorhexis4 the anterior capsule at the time of wound construction or side
(Figure 2). The initial puncture in the anterior capsule is made port construction respectively and subsequently capsulorhexis
with a bent 26 G needle or with the tip of the forceps itself. This forceps or McPherson forceps can be used to lift and rotate the
creates a small flap which is folded over and then pulled by the flap to complete the capsulotomy (Figure 4).
forceps in a circular motion so that force at the point of tear is
tangential to the circumference of the circle. Consequently, the Capsulorhexis with Vitreo-Retinal Forceps
tear is extending by shearing rather than by stretching. This
elevation off the plane of the tear further assures that the tearing The capsulorhexis can also be performed with the help of micro-
force is applied as ‘shear’ rather than ‘stretch’, thus facilitating the capsulorhexis or an intravitreal forceps (Figure 5). The advantage
24 DOS Times - Vol. 13, No.1, July 2007
Figure 3. The Technique of Forceps capsulorhexis with viscoelastic injection through the side port.
Figure 4. Anterior capsule puncture with 3.2 keratome followed by capsulorhexis with Utratas capsulorhexis forceps.
of this forceps is that it can be introduced into the anterior chamber needle to initiate the cut or to put the I/A probe tip under the
through the side port incision and there is no leakage of viscoelastic margin of the capsule and insert the tip of a 26 g needle into the
during the procedure. Special microforceps have been devised for orifice of the probe, such that it causes a small tear at the capsule
use during Microincision cataract surgery / phakonit. margin without any chance of damaging the posterior capsule
(if done after nucleo-cortical removal before IOL insertion).
Two-staged Capsulorhexis The safest time for capsulorhexis enlargement is after IOL insertion
as the posterior capsule is well protected.
In this procedure5 the original capsulotomy is just large enough to
admit the smaller endocapsular phaco probe and a second A two-staged capsulorhexis is particularly useful:
instrument for lens manipulation. The small capsulorhexis can be
enlarged after phacoemulsification and cortical aspiration. After • In patients with small pupils, when an originally small
the lens material is removed, the small initial opening is converted capsulorhexis requires subsequent conversion to a larger
into a larger one, of the desired diameter, while still maintaining capsulorhexis.
the continuous tear edge.
• When the original capsulorhexis is made inadvertently small.
The second capsulotomy is started with a tangential snip on one
side of the capsule edge with a Vannas scissors. An oblique curved • For corneal endothelial protection in intercapsular and
cut (curving towards centre) is advised to incline the tear in a endocapsular cataract extraction.
circumferential fashion. Successful performance of this step
requires the use of a viscoelastic agent in the anterior chamber Disadvantage of a Small Capsulorhexis
and in the lens capsule (if performed after phacoemulsification
and cortical aspiration). It is important to prevent the margin of A small capsulorhexis makes each step of the surgery more
the capsule opening from folding over or under the scissor tip, so difficult and prone to complications. The following problems
as to prevent a V-cut. Extreme caution is warranted because this may be faced by the surgeon while operating within a small
point may create an irregularity in the line of the cut and such a capsular opening:
notched cut destroys the integrity of the continuous tear.
• Injury to capsule margin by phaco tip
Once the tangential cut is successfully achieved, the second
continuous tear is then extended, using Utrata forceps to complete • Damage to the capsule during chopping
a larger circle, which is centered in the pupil, and is of the desired
diameter. The forceps enlarges the original capsulotomy by • Inability to prolapse the nucleus out of the bag for chopping
removing a strip or ribbon of additional capsule (Figure 5).
• Aspiration of the capsule with zonular dialysis
Other options to extend a small capsulorhexis are by using a 26 G
• Difficulty in removing sub-incision cortex
• Diificulty in putting the IOL into the capsular bag.
• Anterior capsule contracture
www.dosonline.org 25
• Increased posterior capsule opacification bag anteriorly is aspirated easily without interrupting the
capsulectomy technique. The capsular opening is enlarged using
• Capsular phimosis occluding pupillary axis the cutter in a gentle circular fashion. The cutter is kept just anterior
to the capsular edge, aspirating the capsule up into the cutting
• Difficulty in viewing peripheral retina on indirect port rather than engaging the capsular edge directly (Figure 7).
ophthalmoscopy
Size of Capsulorhexis
• Late bag dislocation (esp. pseudoexfoliation)
The capsulorrhexis diameter should be 0.5 mm to 1.0 mm smaller
Anterior Vitrectorhexis than the IOL optic diameter. This allows for an adhesion between
the anterior lens capsule and IOL optic and prevents epithelial cell
Anterior vitrectorhexis (mechanized capsulectomy) is another migration under the optic, thereby preventing Posterior capsule
approach to the anterior capsulotomy, especially useful in pediatric opacification11. In eyes with weak zonules, the capsulorrhexis can
eyes7,8. This technique is best performed using a vitrector tip be kept 0.5 mm to 1.0 mm larger than the optic to prevent capsule
attached to a Venturi pump irrigation and aspiration system. contracture12.
Peristaltic pump systems do not cut the capsule as efficiently as
the Venturi pump machines. The vitrectomy probe is introduced Recovering an Escaping Capsulorhexis
through a tight stab incision made at the limbus using an MVR
blade. Irrigation is usually provided with a blunt tip irrigating • After deepening the chamber, attempt should be made to
cannulae through a separate stab incision. A cut rate of 150–300 direct the flap towards the centre of the pupil either with the
cycles per minute is recommended. The vitrector cutting port is cytotome or forceps.
oriented posteriorly and the center of the anterior capsule is
aspirated up into the cutting port to create an initial opening. Any • Disinsert any zonular attachments at the site of the flap.
nuclear or cortical material that spontaneously exits the capsular
Figure 5. Capsulorhexis with intravitreal Forceps
Figure 6. Enlargement of a small capsulorhexis
26 DOS Times - Vol. 13, No.1, July 2007
Figure 7. Anterior Vitrectorhexis
• If this is not possible, cut the capsule at the escape point using 6. Pandey SK, Werner L, Escobar-Gomez et al. Dye enhanced cataract
a curved microscissors to redirect the opening back to the surgery. Part 3: Posterior capsule staining to learn posterior continous
initial route. curvilinear capsulorhexis. J Cataract Refract Surg
2000; 26 (10): 1066-71.
• One can even start a new rhexis in another position working
in a different direction this time to join up with the first rhexis 7. Wilson ME Jr. Anterior lens capsule management in pediatric
at the escape point. cataract surgery.Trans Am Ophthalmol Soc. 2004;102:391-422.
• If available, newer devices like radiofrequency endodiathermy 8. Wilson ME, Bluestein EC, Wang X, et al. Comparison of mechanized
and fugo blade can be used in such case12,13,14. anterior capsulectomy and manual continuous capsulorhexis in
pediatric eyes. J Cataract Refract Surg. 1994;20:602-606.
References
9. Rao SK, Padmanabhan P. Capsulorhexis in eyes with phacomorphic
1. Gimbel HV, Neuhann T: Development, advantages and methods of glaucoma. J Cataract Refract Surg 1998; 24 (7): 882 – 4.
the continuous circular capsulorhexis technique. J Cataract Refract
Surg 1990; 16:31-37. 10. Masket S: Postoperative complications of capsulorhexis. J Cataract
Refract Surg 1993; 19:721-23.
2. Pandey SK, Werner L, Escobar-Gomez et al. Dye enhanced
cataract surgery. Part 1: Anterior capsule staining for capsulorhexis 11. Davison JA: Capsule contraction syndrome. J Cataract Refract Surg
in advanced/white cataract. J Cataract Refract Surg 2000; 1993; 19:582-89.
26 (10): 1052-59.
12. Gassmann F, Schimmelpfennig B, Kloti R. Anterior capsulotomy
3. Arshinoff S: Mechanics of capsulorhexis. J Cataract Refract by means of bipolar radio-frequency endodiathermy. J Cataract
Surg 1992; 18:623-628. Refract Surg. 1998;14:673-676.
4. Dada T, Sethi H. Forceps capsulorhexis. J Cataract Refract 13. Comer RM, Abdulla N, O’Keefe M. Radiofrequency diathermy
Surg. 2002 Aug;28(8):1491. capsulorhexis of the anterior and posterior capsule in pediatric
cataract surgery: Preliminary results. J Cataract Refract
5. Gimbel HV: Two staged capsulorhexis for endocapsular Surg. 1997;23:641-644
phacoernuisi-fication. J Cataract Refract Surg 1990; 16:246-49.
14. Singh D. Use of the Fugo blade in complicated cases.
J Cataract Refract Surg. 2002 Apr;28(4):573-4.
First Author
Tanuj Dada MD
www.dosonline.org 27
Hydro Procedures Cataract
Tushar Agarwal MD, Asim K. Kandar MD, DNB, Rasik B. Vajpayee MS, FRCSEd
Hydrodissection was first developed by Michael Blumenthal Hydrodelineation
as an aid to manual or nonultrasonic small incision cataract
surgery.1 The term “hydrodissection” was coined by Faust in 1984.2 Separation of the inner hard-core endonucleus from the epinucleus
Initially developed for small incision cataract surgery, this by fluid injection is called hydrodelineation (Figure 3). The term
technique was later adapted by the phacoemulsification surgeons hydrodemarcation is also used for this separation.
to enable the separation of the corticocapsular adhesions and
allow nuclear rotation so as to allow safe in the bag nuclear Surgical Technique
emulsification.
Hydrodissection maneuver should be done through the main
Surgical Anatomy of the Crystalline Lens incision. Hydrodissection from the paracentesis opening is avoided
as this causes an increase pressure build up within the eye, which
To understand the concept of hydroprocedures, one needs may lead to a posterior capsule “blow out” or iris prolapse. This is
to familiarize oneself with the anatomy of the lens, which is avoided by using the main clear corneal tunnel for hydrodissection,
briefly discussed here. For the purpose of the cataract surgery, which allows injected fluid to escape from the eye if necessary.
the crystalline lens may be considered to have three zones
(Figure 1).3 An optimally sized capsulorhexis of 4.5 to 5.5 mm is mandatory as
the presence of an adequate anterior capsular flap aids in complete
Zone 1 (Hard Core Nucleus): This is the innermost central core. hydrodissection. The posterior lip of the corneal tunnel/the main
Also known as the “endonucleus” or “inner nucleus”, it cannot be incision should be depressed to cause egression of the ophthalmic
aspirated but can only be expressed or fragmented. viscosurgical device (OVD) so as to create space for the fluid to be
injected during the hydroprocedures. First the capsule is tented
Zone 2 (Epinucleus): This is the intervening zone between the with a hydrodissection cannula. BSS is then injected between the
soft superficial cortex and the hard epinucleus. It is also known as capsule and the posterior cortex with a 28-gauge cannula on 1 cc
the cortical zone or the outer nucleus. Being soft, it can either be syringe with its tip near the equator. Only 0.5 ml of fluid should be
aspirated or expressed. taken at a time. A fluid wave is seen traversing behind the nucleus
and the posterior cortex of the lens and the red reflex becomes
Zone 3 (The Superficial Cortex): This is an array of soft dull. The nucleus is raised upwards and may also prolapse out of
interdigitating lens lamellae, which cannot be fragmented or the bag, especially if the size of the capsulorhexis is large.
expressed but only aspirated. Being outermost, it encompasses Hydrodissection in the subincisional or the 12 o’ clock region may
both the endonucleus and the epinucleus and covers them like a be done either through the side-port using the same cannula or
shell. Surrounding the superficial cortex is the capsular bag with through the main wound with a J shaped cannula.
the subcapsular epithelium.
Although some surgeons recommended single-site hydro-
Terminology dissection, multiple quadrant hydrodissection is more effective in
obtaining a maximum fluid shear effect.5 - 8 Multiple-quadrant
The various hydromaneuvers, which have been described, are as hydrodissection also helps to break corticocapsular adhesions
follows: which are a common association in hard and brunescent cataracts.
(1) Conventional hydrodissection
(2) Cortical cleavage hydrodissection
(3) Hydrodelineation (or hydrodelamination or hydro-
demercation)
Hydrodissection
Conventional hydrodissection - Traditionally, the term
hydrodissection implies the injection of fluid into the cortical layer
of the lens to separate the lens epinucleus and nucleus from the
cortex and the capsule (Figure 2).
Cortical cleavage hydrodissection – Described by Dr.Howard Fine
in 19924, this technique is designed to cleave the cortex from the
lens capsule, thus leaving it attached to the epinucleus.
Dr. Rajendra Prasad Centre for Ophthalmic Sciences, Figure 1. The three zones: nucleus, epinucleus and cortex,
All India Institute of Medical Sciences, (1) Plane of hydrodissection,
New Delhi-110029 (2) Plane of hydrodelineation.
www.dosonline.org 29
Figure 2. Hydrodissection Figure 3. Hydrodelineation
Signs of complete hydrodissection: In such an event, it is advisable to enlarge the incision and
convert such a case to extracapsular cataract extraction to
1. Visualization of the fluid wave, which can be seen going prevent a posterior capsular tear, especially in the hands of a
underneath and around the lens nucleus. novice surgeon. However, in experienced hands phaco-
emulsification may be undertaken with extreme caution without
2. The red reflex becomes dull attempting a vigorous nuclear rotation and only after minimal
manipulation.
3. The nucleus moves forwards
4. The capsulorhexis appears to become larger in size Posterior capsular tear: The tear of posterior capsule by the fluid
wave may occur in cases where the anterior chamber has not been
5. The capsulorhexis margins becomes more prominent evacuated prior to the hydroprocedure by depressing the scleral
lip downwards, to cause the egress of the ophthalmic viscosurgical
Hydrodelineation device (OVD). It can also occur if hydrodissection is attempted
from a paracentesis, which can lead to posterior capsule “blow
Hydrodelineation cannula is passed into the nucleus until it meets out” or iris prolapse.7
resistance and the fluid is injected after withdrawing the cannula,
a fraction of a millimeter. The signs of complete hydrodelineation Yeoh has described the “pupil snap” sign of posterior capsular tear
are the shallowing of the anterior chamber, free rotation of the which may occur during hydrodissection. The pupil suddenly
nucleus and the appearance of as complete golden ring. Very often constricts if a posterior capsular tear occurs during a
an incomplete ring may only be present. hydrodissection procedure.9 This can be prevented by attempting
a gentle hydrodissection at multiple sites and using fewer amounts
Signs of complete hydrodelineation: of BSS at one injection site (not more than 0.2-0.3 ml).
1. Appearance of golden ring Additionally, the posterior capsular tear may also occur due to an
extension of an irregular edge of a keyhole capsulorhexis or in
2. The anterior chamber becomes shallow cases of posterior polar cataract.
3. The nucleus moves forward
4. The appearance of radial splits may be present in the nucleus Hydrodissection in high risk eyes: Hydrodissection in cases of
advanced cataract should be done with special caution because
Complications During Hydromaneuever the cataract’s large bulk and the opaque lens substance may
camouflage a preexisting posterior capsule defect.10
A number of complications may occur while performing Hydrodissection is also contraindicated in conditions such as
hydroprocedures. These may include: posterior polar cataract and pre-existing posterior capsular
defects.11, 12 Ota et al recommended caution in cases of elderly
Prolapse of the nucleus out of the bag: This occurs especially in patients which have a long axial length or pseudoexfoliation as
cases where a larger capsulorhexis has been made. The nucleus in dislocation of the lens nucleus have been reported in vitreous
such cases has to be frequently nudged in the bag, during the cavity.13
procedure of nuclear emulsification by using the second instrument
such as a chopper from the side port. It should also be done cautiously in cases where compromised
zonules may occur such as the elderly, retinitis pigmentosa and in
Extension of an irregular capsulorhexis: This may occur especially cataracts in cases of previously vitrectomized eyes or following
if a large amount of fluid has been used differentially in various vitreoretinal surgery with silicone oil injection.3
directions or it may also occur due to the injury with the edge of
the cannula.
30 DOS Times - Vol. 13, No.1, July 2007
Advantages of Hydromaneuevers 5. Gimbel HV. Hydrodissection and hydrodelineation. Int Ophthalmol
Clin. 1994 Spring; 34(2):73-90. Review. No abstract available.
Hydromaneuvers have been developed to facilitate a safe and
successful phacoemulsification surgery. They help in the following 6. Vasavada AR, Singh R, Apple DJ, Trivedi RH, Pandey SK, Werner L.
maneuvers: Effect of hydrodissection on intraoperative performance:
randomized study. J Cataract Refract Surg. 2002 Sep; 28(9): 1623-
Rotation of the nucleus: The hydromaneuvers especially help to 8.
mobilize and rotate the nucleus within the capsule. This prevents
the transmission of forces exerted on the nucleus during surgical 7. Koch DD, Liu JF. Multilamellar hydrodissection in
maneuvers from being transmitted to the capsule or zonules. This phacoemulsification and planned extracapsular surgery. J Cataract
decreases the risk of zonular dialysis and posterior dislocation of Refract Surg. 1990 Sep; 16(5):559-62.
the nucleus during phacoemulsification
8. Hurvitz LM. Posterior capsular rupture at hydrodissection. J Cataract
Debulking of the Nucleus: The use of hydromaneuvers decreases Refract Surg. 1991 Nov; 17(6): 866. No abstract available.
the volume of the nucleus to be emulsified so that the
phacoemulsification time is decreased. It also decreases the use of 9. Yeoh R. The ‘pupil snap’ sign of posterior capsule rupture with
irrigation-aspiration by leaving lesser amount of cortex after hydrodissection in phacoemulsification. Br J Ophthalmol. 1996 May;
epinucleus removal. In a study by Vasavada et al, it was shown 80(5): 486. No abstract available.
that the nucleus and cortex removal times were reduced by 25%
and 66% respectively in eyes in which hydrodissection was done as 10. Singh R, Vasavada AR, Janaswamy G. Phacoemulsification of
compared to the eyes in which no hydrodissection was done.6 brunescent and black cataracts. J Cataract Refract Surg. 2001 Nov;
27(11): 1762-9.
Safety Cushion: The process of hydrodelineation provides a
cushion of semi-soft epinucleus during the process of 11. Vasavada A, Singh R. Phacoemulsification in eyes with posterior
phacoemulsification of the hard nucleus and this prevents the polar cataract. J Cataract Refract Surg. 1999 Feb; 25(2): 238-45.
occurrence of the posterior capsular tears. Further, the epinucleus
shell has shielding effect as it keeps the capsular bag stretched and 12. Osher RH, Yu BC, Koch DD. Posterior polar cataracts: a
prevents its collapse, this decreases the chances of capsular and predisposition to intraoperative posterior capsular rupture. J Cataract
zonular rupture and the contact between the capsular bags with Refract Surg. 1990 Mar;16(2):157-62.
the phacoemulsification tip is also prevented.
13. Ota I, Miyake S, Miyake K. Dislocation of the lens nucleus into the
Cortical clean up: The hydroprocedures help in loosening of the vitreous cavity after standard hydrodissection. Am J Ophthalmol.
cortical material and consequently aid in cortical clean up. 1996 Jun; 121(6): 706-8.
Decreased posterior capsule opacification: Cortical cleaving 14. Apple DJ, Solomon KD, Tetz MR, Assia EI, Holland EY, Legler UF,
hydrodissection helps to remove the lens epithelial cells (LECs), Tsai JC, Castaneda VE, Hoggatt JP, Kostick AM. Posterior capsule
thereby reducing incidence of posterior capsular opacification opacification. Surv Ophthalmol. 1992 Sep-Oct; 37(2): 73-116.
(PCO). This is because the shearing effect of the fluid wave created Review.
during these procedures detaches equatorial LECs from the
adjacent equatorial capsule, allowing their easy removal from the 15. Apple DJ, Peng Q, Visessook N, Werner L, Pandey SK, Escobar-
eye during phacoemulsification.14-18 Gomez M, Ram J, Auffarth GU. Eradication of posterior capsule
opacification: documentation of a marked decrease in Nd:YAG
References laser posterior capsulotomy rates noted in an analysis of 5416
pseudophakic human eyes obtained postmortem. Ophthalmology.
1. Blumenthal M, Ashkenazi I, Assia E, Cahane M. Small-incision 2001 Mar; 108(3): 505-18.
manual extracapsular cataract extraction using selective
hydrodissection. Ophthalmic Surg. 1992 Oct; 23(10): 699-701. 16. Peng Q, Apple DJ, Visessook N, Werner L, Pandey SK, Escobar-
Gomez M, Schoderbek R, Guindi A. Surgical prevention of posterior
2. Faust KJ. Hydrodissection of soft nuclei. J Am Intraocul Implant capsule opacification. Part 2: Enhancement of cortical cleanup by
Soc. 1984 Winter; 10(1): 75-7. focusing on hydrodissection. J Cataract Refract Surg. 2000 Feb;
26(2): 188-97.
3. Vajpayee RB. Hydromaneuvers in phacoemulsification and cortical
clean up. In : Phacoemulsification, laser cataract surgery and foldable 17. Vasavada AR, Dholakia SA, Raj SM, Singh R. Effect of cortical
IOLs. Eds. Agarwal S, Agarwal A, Sachdev MS, Mehta KR, Fine IH, cleaving hydrodissection on posterior capsule opacification in age-
Agarwal A. 2nd edition. Jaypee Bros Medical Publishers, New Delhi related nuclear cataract. J Cataract Refract Surg. 2006 Jul; 32(7):
2000; 12:122-29. 1196-1200.
4. Fine IH. Cortical cleaving hydrodissection. J Cataract Refract Surg. 18. Vasavada AR, Raj SM, Johar K, Nanavaty MA. Effect of
2000 Jul; 26(7):943-4. No abstract available. hydrodissection alone and hydrodissection combined with rotation
on lens epithelial cells: surgical approach for the prevention of
posterior capsule opacification. J Cataract Refract Surg. 2006 Jan;
32 (1): 145-50.
First Author
Tushar Agarwal MD
www.dosonline.org 31
Basic Phacodynamics Cataract
Archana Sood MS, Parul Sony MD, Satish C.Gupta MS
The Invention • Followability means the ability of the phaco tip to attract
nuclear pieces. The more the flow rate, more the followability
"The author will find a way to remove cataract through a tiny incision
eliminating the need for hospitalization and dramatically shortening • Holding ability is the ability of the tip to hold the nuclear piece
the recovery period" to enable chopping. It is dependent on the needle bevel angle,
the placement of tip at a correct angle to the nuclear piece
These were the words in a project written by Dr Charles Kelman, and the post occlusion vacuum dynamics
for which he received a grant from the John A Hartford
foundation, and heralded the greatest discovery of modern cataract Foot Pedal Functions
surgery(1967).
• Irrigation =Foot Pedal Position 1
The various experimental devices he tried were Electric toothbrush,
Rotating device, Meat grinding butcher device, Microblenders and • Irrigation+ Aspiration= Foot Pedal Position 2
Cutters. The first success was the Ultrasonic Dental drill ,the idea
of which originated when he was sitting in a dental clinic getting his • Irrigation+ Aspiration+ Fragmentation= Foot Pedal
filling removed. Position 3
This led to the development of the first phaco machine (Kelman • Reflux gate is usually on the lateral left side or superiorly
Cavitron Unit) in which cataract was fragmented with ultrasonic
energy through a microincision, simultaneously supported by • Rightsided/lateral gates are for changing programmes
irrigation inflow and aspiration outflow systems
Dual linear foot pedals(e.g. Bausch and Lomb Millennium) allow
Machine Terminology a Yaw movement i.e Side ways movement at any stage of position
2 to allow phaco power to start before reaching the maximum
• Phaco Power, this is expressed in % and is the stroke length of aspiration. (Figure1)
the phaco tip. An increase in phaco power results in an
increased stroke length and not an increase in frequency, Irrigation Systems and Bottle Height
which remains the same for a particular machine for e.g. an
increase in power from 40% to 60% will increase the stroke Standard bottle height is usually 65cm above the eye level to enable
length i.e. the length or amplitude of the to and fro motion a fluidic balance which is the balance between inflow and outflow
but frequency remains 40 Khz i.e 40,000 cycles/sec. of fluid for maintaining a stable anterior chamber as well as
protection of cornea and posterior capsule. An increase in flow
• Vacuum is the suction force applied by the peristaltic or venturi rate or vaccum necessitates an increase in bottle height to prevent
pump. The parameter shown on the panel suggests the surge and collapse of the anterior chamber. Microincision cataract
maximum preset levels e.g.120 mm Hg. surgeries requiring sleeveless tips and irrigating choppers, require
higher bottle heights or air pumps to increase the inflow.
• Flow Rate is the rate of fluid flowing out of the eye (in cc/min), (Figure 2)
and not into the eye as is commonly perceived. Flow rate and
vacuum are interlinked.
• Rise Time is the time taken for the vacuum to rise to the
preset maximum, when the tip is occluded with nuclear matter,
to facilitate its suction into the tip.
• Pump speed is the speed of the rotation of the peristaltic pump.
A demand for higher flow rate and vacuum necessitates an
increase in the pump speed.
• Venting means breaking of vacuum. Analogy: When we hold
a glass to our mouth and suck in all the air a vacuum is created
and the glass remains firmly stuck to the mouth. When the
vacuum needs to be broken, we push some air into the glass.
• Compliance-Is inversely related to the outflow resistance. the
more the compliance (e.g stiffness and diameter of the tubings
lessen the resistance.
Venu Eye Institute & Research Centre, Figure1. Dual linear foot pedal
1/31, Sheikh Sarai, Phase-2,
New Delhi-110017
www.dosonline.org 33
Aspiration Systems • A Valve opens and fluid/air is sucked in
The various types of Pumps are : • The diaphragin is pushed in and a second valve opnes
• Peristaltic • This exhausts fluid/air
• Venturi Venting Systems
• Diaphragmatic In order not to exceed the preset vacuum limit, all pumps require
Features of Peristaltic Pump a venting system to break the vacuum
• Slow buildup of vacuum, large safety margin
• More controlled fluidics Air Venting
• Vacuum builds only on occlusion
• Surge is more Features:
• Characterised by high time delays for detecting vacuum
change
• Good for beginners
• Nucleus has to be mechanically approached (Figure 3)
Features of Venturi Pump
• Linear and rapid built up of vacuum, even without occlusion
• Good followability of tissue
• Nuclear and cortical matter easily attracted to tip
• Surge is less as vacuum is constant even on occlusion
• Rise time is fast therefore safety margin is lesser
• Good for experienced surgeons (Figure 4) Figure 3. The peristaltic pump uses a rotating wheel
Features of Diaphragmatic Pump with rollers to pinch off segments of the aspiration tubing.
• Similar to venturi pump This moves discrete volumes of fluid through the tubing at
• A Flexible diaphragm is pulled out by rod and motor a set rate of flow. A. Atmospheric pressure B.Inches of water
C. Aspiration line ml/min D. Pump E. Collection Jar.
Figure 2. The effect of bottle height(A) on IOP is reduced in Figure 4. The venturi pump sends gas through the tubing
proportion to fluid loss from the eye. B.Fluidity of the eye with an aperture that controls the rate of gas flow and therefore
C.Evacuation pump D. Exit fluid.
the pressure A.Surgeons foot pedal B.Compessed gas
34 C.Iris diaphragm D. Aspiration line E.Aspiration Fluid.
DOS Times - Vol. 13, No.1, July 2007
Figure 5. Phaco handpiece. Left;Tip bevel angles. • Responds slowly to compensate vacuum surge
Figure 6. Phaco tip designs : Kelman tip, Mackool Tip, • Air venting increases compliance of the system, which
ABS turbosonic tip, Flared Cobra tip. increases surge
Figure 7. Phaco power: The longer strokes of the phaco needle Fluid Venting is better than Air Venting
result in more power (A) Ultrasound stroke length
(B) Aspiration (C)Irrigation. • Characterised by low time delays detection for vacuum change
www.dosonline.org • Responds faster to compensate vacuum surge
• Compliance is less in a system with fluid vents with lesser
surge as a result
Phaco Handpiece Characteristics
• Titanium Tip
• Usual Frequency 40 Khz
• Usual Amplitude 3/1000 of an inch
• Piezoelectric Quartz Crystal
• Diameter (19 G-0.9mm,20G-0.6mm)
• Bevel angle (0,30,15,30,45)
The crystal converts the electrical energy into ultrasonic energy
which causes the tip to vibrate mechanically and fragment the
nucleus. (Figure 5)
Phaco Needle Tip Designs
• 19G (standard) 0.9mm (Figure 6)
• 20G (microtip) 0.5-0.9mm-enhances the irrigation flow,
reduces the thermal risk and suppresses surge
• Kelman Tip : Is angled for increased cutting efficiency &
improved manipulation of nucleus
• Mackool (Alcon tip): Inner sleeve is provided for added
thermal protection
• Tip with Aspiration bypass system (tiny hole in the needle,
which causes inflow of fluid into the needle from the irrigation
sleeve upon occlusion, to pevent suuden inflow of fluid when
occlusion breaks.
• Flare Tip head design with rigid silicon tube increases the
holding force and emulsification capacity.
Phaco Power
• 100% power =Max stroke length
• 50% power =1\2 stroke length
• Frequency remains same
• Chatter is the yo-yo like movement of nuclear fragments at
the tip due to attraction and repulsion forces
• Sweet spot-exact spot at foot pedal at which the nuclear piece
gets attracted to the tip and gets emulsified (Figure 7)
Phaco Power Delivery
Grade of nucleus x 15 + 25 = Phaco power. Phaco acts by:
• Direct impact
35
Figure 8. Phaco modes; Continuous mode; Figure 9. Rise time time taken for vaccum to build up to max.
Pulse mode; hyperpulse mode. preset levels is least in Venturi pump.
• Shock waves d. Burst mode
• Cavitation energy Was Introduced by AMO Diplomax.
• Pulser power It delivers single momentary pulse of phaco energy.
Phaco Modes Can be delivered individually at an interval of 1-2 seconds or in
rapid succession (Multiburst) via foot pedal control.
a. Constant mode
This mode provides a surrounding tight seal around the nucleus-
Means the phaco tip is continuously vibrating to provide a constant individual bursts of phaco are ideal for impaling and gripping
phaco power. This mode (programme 1) is used for trenching as dense nuclear material for chopping in the 2nd programme.
full power is required to cut a trench in the nucleus. (always on; no
off time) (Figure 8) Higher powers are prefed for dense nuclei.
b. Pulse mode e. Occlusion mode
Means phaco tip is vibrating 50 % of a second i.e 500ms on and Def: Ability to change both pump speed (aspiration flow rate) &
500ms off i.e on time =off time. This mode is used in the direct power modulation pre and post occlusion.
chop and the 2nd step of stop and chop ,as pulses of phaco help
the piece to stick to the tip also helped by the increased aspiration Example1: Pre occlusion)- C/L* mode (20%dc) used to draw piece
in programme 2. towards tip as off time24s on time 6s.
Duty cycle or DC (means the % of time phaco tip performs its Post occlusion C/F*(33% dc) starts & helps provide more
duty) ultrasound to emulsify the nuclear piece.
Continuous mode=100% DC Example 2: Epinucleus mode-
Pulse mode=50% DC Upon occlusion flow rate=32cc/min; Post occlusion flow rate comes
down to 20cc/m to decrease surge.
D C= On time/On + off time x 100
Effective Phaco Time
c. Hyperpulse mode (cold phaco, whitestar, micropulse)
• EPT=%power x total time of surgery.
(on time < off time) e.g • E.g: 60/100 of 120 sec = 72sec.
On T=6ms; Off T=12ms Rise Time
Duty cycle=6/18x 100=33% • Is a measure of how rapidly vaccum builds up once occlusion
Pulses/sec=1000ms/18=55 has occurred.
Hyperpulse mode may have 20%,33%,60%DC etc • Faster rise time with venture pumps.
• Lesser safety but.
• Energy is delivered in extremely brief, microsecond pulses, • Time efficient (Figure 9).
interrupted by rest periods
• Micropulse length and rest period length are independently Surge, Anti-Surge, AC depth
variable • Surge: means collapse of A.C after occlusion breaks
• Full ultrasound cutting ability is retained (Figure 10).
36 DOS Times - Vol. 13, No.1, July 2007
Table 1 : Machine Setting Ideas(Stop and chop)
Prog Flow rate Vaccum Power Acc.
(cc/min) mm of Hg To type of
cataract
1-trench 15 30
2-chop 30-40 30-70%
120-300 (note the
manifold increase 30-70%
in vaccum)
• Holding the nucleus
• Chopping
High vacuum gives better holding ability but surge may occur
Application to Phaco Procedures
Figure 10. Surge phenomenon • Sculpting or trenching (Table 1)
• Chopping (Table 1)
• Epinucleus aspiration
• Cortical removal
• Surge control: Epinucleus Removal
i) Raise Bottle Height, • Vaccum is lowered below programme 2 vaccum levels to
ii) Lower Flow rate. prevent surge and posterior capsular rent
iii) Resistant tubings.
iv) Smaller phaco tips. • Very little or no Phaco power needed
v) Larger irrigation ports.
vi) Lower Vaccum. Cortical Aspiration
Compliance • Vaccum parameters-300-400mmHg
• Irrigation support
• More the compliance -more surge, less responsiveness of the • Foot pedal control
system.
Machine Settings and Cataract Types
• Lesser the compliance-Less surge, more responsiveness of
the system. • The very softs-lower the power (25%), no trenching, go to
phaco mode 2 with smaller duty cycle, moderately high vaccum
• Air vents increase the compliance, decrease the and flow rate
responsiveness.
• The very hards-high power for trenching,burst mode for
• Fluid vents decrease the compliance, responsiveness of system direct chop, hyperpulse in both linear and pulse, longer duty
is more. cycle
Followability Troubleshooting and Adjustments
The ability for aspiration flow to draw the nucleus to the phaco • Surge: Lower both flow rate & vacuum
needle Increase bottle height
Check the machine height level
Higher pump speed = Higher flow
= Higher Followability (normally) • Leaking Tip: Check the pump pinch cock
• No aspiration: Flush the Aspiration tube to remove blockage
Holding Ability • Phaco stops: Retune the machine,handpiece, tip
• Too much surge- tubes have become compliant-need change/
• Vacuum builds up
• Full Occlusion machine needs servicing
• Air bubbles-Check for loose tubings
www.dosonline.org 37
• Priming not successful-check all attachments • Surge control by small internal diameter aspiration line tubing
• If the tip is not holding the nuclear piece in prog 2 of a whitestar • ABS needle
machine: Increase the vaccum and flow rate also raise the • Large diameter irrigation supply, large irrigation ports
bottle height, decrease the PPS and duty cycle to give more
off time thus aspiration force to hold the piece • 2 dedicated computers for fluidics & ultrasonics control
Some Features of AMO Sovereign Phacoinnovations
• Was Introduced in 1999 • Erbium Yag Laser Phaco-The laser produces a wavelength of
• Has Fluid venting for surge control 2.94 micron, which lies in the infra red spectrum and is
• Has Low compliance with a faster responding system absorbed by water, therefore lessening the thermal injury.
• Divide &Conquer, Stop & chop, Direct chop, Bimanual
• Nd Yag laser phaco (1064nm)-a shock wave is generated which
phacomodes are provided does not produce heat and thus facilitates smaller incision
• 4 phaco memory settings site with a sleeveless tip.
• Foot pedal with lateral gates ( R&L)
• Peristaltic + venturi pumps • Sonic Phaco-Sonic waves emanate less heat as there is no
• Whitestar cold phaco, variable duty cycle settings,*Use of codes cavitation effect
A,B,C….For 2,4,6ms…. • Neosonixs-This is a hybrid modality which includes a low
• RTS(Ramp threshold speed): Adjustable pump starts to frequency oscillatory movement +- high frequency ultrasound
power
decelerate when 80% of preset vacuum is reached
• Surge control: stiff wall tubings, fluid venting • Whitestar-cold phaco, hyperpulse as already explained in the
• Smart pump: Monitors vaccum-dedicated microprocessor text
computers more precisely regulates pump to prevent surge • Catarhex-A tiny rotary impeller inside the capsular bag is
• Multiburst: 80ms long bursts at 2.5 sec intervals at a preset introduced through a 1mm capsulorhexis. This impeller rotates
at 60Khz and causes expansion of capsular bag with rotation
power- as foot pedal is depressed freq of bursts inc to 4 b/sec of the nuclear complex rotary
Some Features of Alcon Legacy • Aqualase-BSS pulses at 50-100 Khz are used to dissolve soft
cataracts
• Introduced in 1993, has upgraded hardware and software
• Can set individual programs for 96 doctors with 4 memories • Torsional phaco-The tip moves side to side instead of forward
and backward at 32Khz, the resultant frequency becoming
each 64Khz as the tip cuts both ways. Lesser heat is generated at
• Neosonix tip: Low freq oscillatory movements standard high the corneal tunnel as only the tip of the phaco needle vibrates
side to side e.g Alcon Infiniti
frequency ultrasound
• Phaco modes available: References
Pulse mode:15 pps, Fixed dc of 50% 1. Fine Howard I. Phacoemulsification - New technology and Clinical
Burst mode:30ms burst width at int of 2.5 seconds Applications. Thorofare USA, SLACK incorporated ist editon 1997
Occlusion mode: phaco power reduced on occlusion pg 2
• Fluid venting (brisk responsiveness to foot pedal input)
• Less compliant tube between cassette and hand piece 2. Siebel B S. Machine Technology. Phacodynamics. 2005.Thorofare
• High peristaltic pump speed mimics venturi USA, SLACK incorp. 4th edition. Pg2-15
3. Vajpayee,R.B, Sharma N, Pandey S, Titiyal J.Phacodynamics and
machines; Phacoemulsification Surgery. New Delhi. Jaypee.1st
edition.2005.Pg 118
4. Chang F.D. Phacodynamics of chopping. Phaco Chop. Thorofare
USA. Slack Incorp. 1st edition.2004.Pg.77-117.
First Author
Archana Sood MS
38 DOS Times - Vol. 13, No.1, July 2007
Nuclear Emulsification Cataract
Asim K. Kandar MD, DNB, Namrata Sharma MD, DNB, MNAMS, Jeewan S. Titiyal MD
Though all the steps in phacoemulsification are equally • Depth – The depth must be 80 to 90% of the nuclear thickness
important and necessary, removal of nucleus by in situ for its entire length. The change of gray to red reflex indicates
emulsification is the most crucial for the success. Its removal by adequate depth. Indirect evidence is that the depth of the
ultrasound can be performed using a number of techniques that groove must not exceed two and half times the diameter of
have evolved from Charles D Kelman’s original concept. The the phaco tip (as the thickness of the nucleus is 3.5 to 4.0 mm
technique has evolved because of non-stop development of both and the diameter of the tip including sleeve is 1.0 mm).
the machines and the surgical techniques. The various nucleotomy
techniques are being described in relation to commonly When the right-sized groove is created, the surgeon can
encountered nucleus with Grade II - III hardness. Suitable variations proceed with nucleus fracture.
of nucleus emulsification technique will be suggested for some
difficult situations.1 Nucleofracture
The surgical technique varies from surgeon to surgeon and case • The fracture of the nucleus is obtained by separating the two
to case. It is important to achieve effective nucleus emulsification edges of the groove using the ultrasound tip on one side
without jeopardizing health of other structures and completion of (usually dominant hand) and the second instrument on the
surgery. other side.
Nucleofractis - General Principles • They can be placed either parallel to each other on the edge
of the groove or cross-over.
The modern day technique of nucleofracture has been developed • The nucleus can also be bisected with the help of chopper
to split the nucleus in two pieces and to emulsify nucleus pieces in after stabilizing the nucleus.
the capsular bag. It also has the objective to emulsify moderate to
very hard nucleus without using excessively high ultrasound power • Ideal depth is two-thirds of the groove depth as excessively
for prolong time. Effective nucleofracture allows the surgeon to superficial or deep position will not allow for optimal leverage
shorten ultrasound and surgical times to minimize damage to the necessary for nucleofracture.
corneal endothelium.
With nucleofracture, the nucleus is split into two portions that will
Pre-requisites for nucleus emulsification be emulsified subsequently after achieving multiple smaller pieces.
The surgeon must increase both the tendency of the nucleus to
• Optimal visibility- Clear cornea, adequate dilatation of pupil. approach the ultrasound tip (high flow rate) and the capacity of
the tip to hold on to the nucleus (holding power ie, high vacuum)
• Capsulorhexis – This must be continuous and complete. The to emulsify and be aspirated. This can be obtained by increasing
size should be adequate for nucleus fracture. The anterior the vacuum to 100 to 120 mmHg, flow rate 30 cc/min, and reducing
capsule may be stained with trypan blue dye so that the CCC the mean ultrasound power to 50 to 70% depending upon hardness
edge is visible during the entire phacoprocedure. of nucleus. The initial fracture has to be complete so that we
achieve two bisected pieces without undue pressure to structures
• Hydro procedure – Hydrodissection and hydrodelineation like capsular bag and zonules. In case there is incomplete bisection
must be complete and adequate to allow free rotation of of the nucleus it should be rotated by 180 degrees and separation
nucleus inside the capsular bag and to provide sufficient epi- can be completed. In a hard cataract removal of small piece (a pie)
nuclear cortical cushion during the entire nucleotomy gives space for subsequent separation of the nucleus.
procedure.
• Sculpting – The objective of sculpting is to create one or more If the nucleus is hard, spontaneous occlusion is more difficult and
grooves in the nucleus. They must be wide and deep enough it is facilitated by short bursts of low-power ultrasound. Capture
to allow the surgeon to fracture the nucleus with two-handed of the last fragment with the ultrasound tip can be facilitated by
maneuver. using the pulse mode of the ultrasound. A good viscoelastic is also
necessary in difficult situations.
• Width – Groove must be wide enough for free movement of
ultra sound tip and accessory instrument. Also it reduces Which ever technique is practiced for a case the emphasis is on
bulk of central hard nucleus. effective bisection of the nucleus and subsequent emulsification
of pieces without damaging the zonules, capsule and corneal
• Length – Sulcus must extend just below the capsulorhexis. endothelium.
The extention depends upon hardness of nucleus and the
type of hydro-cleavage done. If there is no hydrodelamination Various types of nucleofractures are described below.
the groove should extend inside the rhexis. Divide and Conquer
Dr. Rajendra Prasad Centre for Ophthalmic Sciences, Following CCC, adequate hydrodissection and delineation
All India Institute of Medical Sciences, is required for divide and conquer nucleofractis phaco-
New Delhi-110029
www.dosonline.org 41
AB C
Figures 1A, B, C. Chip and flip technique (A) After shallow sculpting the inner nuclear rim is removed at 5-6 o’clock position,
(B) Remaining chip of the central nucleus is emulsified, (C) Epinuclear bowl is flipped away from the posterior capsule.
emulsification. Following four basic steps are to be followed– accomplished by pushing toward the right by phaco tip as the
chopper is pushed to the left. The nucleus splits from the center to
• Deep sculpting until a fracture is possible, the superior and inferior rim of the nucleus if the instruments are
held deep in the center. This is done with foot switch at position 2.
• Nucleofractis of the nuclear rim and posterior plate of the
nucleus, Chip and Flip Technique
• Fracturing again and breaking away a wedge-shaped section After central sculpting the nucleus is pushed toward 12 o’clock and
of nuclear material for emulsification the inner nuclear bowel is at 5 to 6 o’clock and the nucleus is
rotated clockwise to sequentially facilitate each hour of rim being
• Rotation or repositioning of the nucleus for further fracturing removed from the 5 to 6 o’clock region. Once the rim of the inner
and emulsifdication.2 nuclear bowl is removed, the second handpiece is brought into
the cleavage plane between the inner nuclear chip and the outer
Crater Divide and Conquer (CDC) nuclear bowl and swept under the chip, elevating it into the center
of the bag and emulsified.5 (Figure 1a, 1b,1c)
This is done in hard cataract. This is called crater divide and conquer
(CDC) technique because of the large crater sculpted, leaving a Stop and Chop
dense peripheral rim to fracture into multiple sections. In CDC
rather than immediately emulsifying, each wedg-shaped section This technique begins with a groove. This produces a space for the
is generally left in place for capsular bag distention. Once the ultrasound tip and the chopper, which will be able to fracture the
fracture is complete, each pie-shaped wedge of nuclear rim is nucleus into two parts. At this point stop and rotates the nucleus
brought to the center of the capsule and emulsified safely. High through 90º, fix the lower half of the nucleus with the ultrasound
flow, high vacuum and low U/S power with 150 or 300 tips is ideal tip and crack is created with the chopper. A number of fragments
for it. As an alternative during CDC, the first sector may be result, which can be easily mobilized from the capsular bag and to
removed before performing additional fracture especially in case be emulsified in the pupillary plane. (Figure 2a, 2b,2c)
of mature white cataract.
Trench Divide and Conquer (TDC) High-Vacuum Phaco Chop
For nuclei with grade 2 to 3 hardness, a central narrow trench is Using high vacuum during chopping further improves nuclear
made instead of crater. The groove should not be too deep so that control and reduces the total ultrasound energy required. High
the instruments are positioned at the center of the groove. The vacuum allows grasping and holding the nuclear wedges and
nucleus is fractured from 6 to 12 o’clock. drawing them toward the central zone of safety before completing
the emulsification. Moreover, the manual energy input from the
Trench Divide and Conquer with “Down Slope” Sculpting phaco chop, combined with the energy input from the high vacuum,
reduces the total amount of ultrasonic energy required. Overall,
It is a slight variation from the traditional sculpting method. By the technique appears to be safer and more controlled. Because
nudging the lens inferiorly with the second instrument, the upper of its efficiency, the nuclear disassembly step becomes substantially
central portion of the nucleus can be sculpted very deeply to the faster than alternative techniques such as quadrant cracking.6-7
point of sculpting directly parallel and close to the posterior
capsule. This allows the tip to remove more of the upper part of Phaco Parameters for the Nucleotomy Steps
the nucleus during sculpting and to reach the posterior pole of the
lens very early for effective fracturing.3,4 This technique is especially Sculpting: moderate phaco power with low flow rate and aspiration.
helpful in small pupil and can also be used to remove a large Continuous linear phaco power
portion of the upper part of the lens. After sculpting, fracturing is
Segment removal: low to moderate phaco power depending on the
42 DOS Times - Vol. 13, No.1, July 2007
hardness of the cataract and high flow and aspiration. Pulse or posterior strands represent posterior epinucleus that has partially
burst mode hardened, with strong adhesion to the posterior nucleus and with
a tough, strandlike quality. When these strands occur, they are
Last piece: Moderate phaco power with low flow rate and aspiration, seen against the red reflex as they bridge between two chopped
use pulse or burst mode nuclear fragments. The surgeon can rotate the phaco chopper 90º
in his or her fingers, then carefully pass the chopper posterior to
Phaco tips: 45 or 30 degree tips for devide and conquer techniques the nuclear fragment and transect the bridging fibers. This
and 30 or 10 degree for direct chop techniques. For faster and maneuver is known as “posterior cracking.”
effective emulsification tips like kelman, kobra or flare tip may be
used. Neosonics and Ozil system require kelman tips. To achieve Crater & chop techniques: The technique of in-the-bag
stronger hold it is better to use micro flow tips. This allows higher phacoemulsification of large, hard and leathery brown nuclear
vacuum and better fluidics. cataract decreases the endothelial damage which is seen with
prolong phaco power used in these hard nucleus. A large crater
Nuclear Emulsification in Challenging Situations9 approximately 6.0 mm diameter is created by down-slope sculpting
up to 90% of nuclear thickness, leaving the outer nuclear rim intact.
Small Pupils The edge of the crater is held with the phaco probe using high
vacuum, and small wedge-shaped pieces are created with a chopper.
Small pupil cases should only be undertaken after the surgeon has These small pieces are emulsified in the space created by the crater.
gained reasonable experience in more straightforward cases with This technique permits in-the-bag phacoemulsification of large
large pupils and moderate-density nuclei. Chopping is preferred brown cataracts without complications.10
over the quadrant cracking or divides and conquer technique
because chopping does not require peripheral passes with the How to Decrease Phaco Power in Hard Nucleus
ultrasound tip, and it is not dependent on a good red reflex.8 Emulsification
It is very important not to damage the pupil during initial steps of Use micro pulse with longer off duty cycle or burst mode phaco
the nucleus emulsification, if there is iris tissue damage the pupil will help. High vacuum phaco with high flow rate for effective
should be retracted by the use of nylon hooks. Use of high viscosity flowbility helps. The second instrument can also be used to stuff
viscoelastics (OVD) helps in maintain the space, pupillary dilataion the pieces. If available use of torsional phaco is effective in
and also prevent endothelial loss. Before attempting decreasing phaco related damage to other structures.
nucleusfracure it is must to have intact CCC and good
hydroprocedure in small pupil case. Once the division is achieved Zonular Abnormalities
subsequent completion of emulsification is easy. In case of any
difficulty it is advised to retract the iris with nylon hooks so that Once experience is gained with phaco chop, it is the preferred
visibility is improved and disaster is avoided. technique in the presence of weak or missing zonules. This situation
occurs most commonly in pseudoexfoliation syndrome or after
The hard Nucleus trauma. Horizontal chopping is advisable as it creates opposing
forces between the two instruments and thus minimizes forces on
Because the nucleus is thick, longer and sharper chopper with 1.75 the zonules.11
to 2 mm tip is recommended.
Proper preoperative assessment is necessary to assess the amount
A very hard brunescent nucleus also tends to have a posterior of the zonular deficiency. CTR or capsular bag stabilization is
“leathery” quality. Chopped fragments have posterior bridging
strands that keep nuclear fragments attached to each other. These
A BC 43
Figures 2A, B, C. Stop and chop (A) Initial groowing; (B) Phaco tip is buried in one of the walls of the groove to stabilize the nucleus, the
chopper is pushed against the other wall to break the nucleus into two pieces (C) Rotation of the nucleus and phaco tip is buried to stabilize
the nucleus, sharp chopper is moved centrally towards phaco tip from periphery for further chopping.
www.dosonline.org
required to maintain the bag stability during phacoemulsification. continue rotating and attempt to chop a new area, concentrating
The phaco parameters need to have moderate flow and aspiration. on proper technique. In addition, the chopper can act as a “finger”
The fluidics should be maintained so that the anterior chamber is to hook around the equator of a fragment and help bringing it
stable throughout the emulsification to avoid further disruption toward the phaco tip in the central zone.
of zonules. If CTR or Cionni ring is being planned it is utmost
important to have intact CCC. If vitreous prolapse occurs it should Posterior Plate
be managed properly with automated vitrector. It is usually encountered in hard nucleus where the initial division
Incomplete Hydro Procedures or bisection could not be complete. Injection of viscoelastic (OVD)
beneath the posterior nuclear plate helps in engaging it to the
It is better to perform direct chop in such situations. In case sculpting phaco handpiece and prevent damage to the posterior capsule.
or trench is practiced dividing or separation has to be gentle. In Experience surgeons might be able to pickup this central plate by
case there is less space as in these cases nucleus will not rotate a vacuum and subsequently phaco is done.
small pie should be removed and subsequently separation will be
possible as now there is more space. Sometimes this removal of Posterior Capsule Rupture
pie also helps in in- situ hydro dissection and nucleus rotation is The most feared complication for beginner is rupture of the
possible.
posterior capsule. Extra care has to be taken to avoid this disaster.
Hypermature Cataract with Free Floating Nucleus Usually it is very difficult to rapture the posterior capsule with a
chopper as the length of the chopper is quite less than lens thickenss.
Most often the nucleus is very hard and floating in long standing The most common cause is decompression of anterior chamber
HMSC. Nucleus bisection or chopping can be made safer in this during nucleus piece emulsification. Uncontrolled surge and
situation by directly impaling the phaco tip at the center of the continuous running phaco near the posterior capsule without the
nucleus with higher parameters. If the float is more and difficult to occlusion of the handpiece tip with nucleus fragment leads to
stabilize the nucleus, viscoelastic may be injected behind the nucleus rupture of posterior capsule. It is some times difficult to detect or
in the bag. Stablization can also be achieved with second instrument. appreciate early rupture of posterior capsule if it happens in the
Corneal Opacity early phase of nucleotomy. Sudden appearance of bright red glow,
and decrease in flowbility of the pieces and vitreous in the chamber
The CCC should be completed with the help of the dye staining. are the signs of capsular rupture. If undetected in time, entire
The trench or crater should be achieved within the area of most nucleus or fragment can dislocate in the vitereous cavity. It is
visible portion so that nucleus division can be easy. The subsequent advisable if the rupture happens early in nucleotomy convert to
emulsification of pieces should also be performed in the most ECCE with the help of vectis and vicoelstic expression of nucleus.
visible area. The basic concept is not to do emulsification with If the capsular rupture is in the late stages with early detection the
poor visibility. tear or rupture can be plugged with viscoelastic (dispersive OVD
like Viscoat) and phaco can be completed. It is advised that the
Endothelial Dystophy surgeon must evaluate the case on the table and take the
In patients with poor endothelial counts it is advisable to perform appropriate steps for the management. In case of vitreous already
the emulsification with viscoelastic specially a viscoadoptive OVD, in the anterior chamber, remaining pieces should be removed
softshell technique is also helpful. Complete the entire phaco in with the help of viscoelastic or vectis and adequate automated
the bag. vitrectomy should be performed.
Last Piece Emulsification Anterior Capsule/Zonular Rupture
The phaco parameters can be lowered specially the vacuum and A more common complication is misjudging the location of the
flow to avoid sudden surge at this stage as there is no barrier to anterior capsule, such that the phaco chopper is anterior to the
posterior capsule. But if the surgeon is comfortable he can peripheral anterior capsule rather than within the capsular bag.
complete without any change in phaco
parameters. Burst or micro pulse mode is Advantages & Disadvantages of Various Modes
preferable at this stage. Help of the second Mode Advantages Disadvantages Applications
instrument in stuffing the piece may also Continuous Simple Repels nuclear Sculpting
facilitate the step. material, increase
Complications of Phaco Chop wound temperature
Multiple Incomplete Chops Pulse Less increase in Can repel Segment removal
wound temperature nuclear material
This usually occurs for two reasons – (1) Burst Less increase in Chopping
not passing the chopper far enough into Hyperpulse wound temperature
the periphery in order to allow the chopper Holds material well Sculpting Bimanual
to hook and engage the equator, (2) Followability with small incision
allowing the chopper to ride up and out of Long off cycle Cool
the nucleus. At this stage be patient, with long off cycle
44 DOS Times - Vol. 13, No.1, July 2007
Comparison between various techniques Disadvantages 2. Gimbel HV. Principles of Nuclear
Fragmentation style Advantages Phacoemulsification. In: Steinert RF, Ed.
Sculpt and Prolapse Easy on bag SlowEnergy close to cornea Principles of Nuclear Emulsification.
Lots of ultrasound power Philadelphia, Pennsylvania, Saunders
2004:153-181.
Divide and Conquer Classic easy to do Lots of ultrasound power 3. Maloney WF, Dillman D: Fractional 2:4
Stop n Chop Energy away from cornea Needs two hands phaco. In Koch P, Davison J, editors:
Can do with one hand Phacoemulsification techniques,
Thorofare, NJ, 1991, Slack, Inc, pp 241-
Fairly easy to do 255.
Vertical Chop Less ultrasound power Hard to do 4. Fine IH.The chip and flip
Needs two hands phacoemulsification technique. J Cataract
Little stress on bag Refract Surg. 1991 May; 17(3):366-71.
Least ultrasound power
Fast Get anterior capsule with 5. Pirazzoli G, D’Eliseo D, Ziosi M, Acciarri
hopper Jig saw problem R. Effects of phacoemulsification time on
the corneal endothelium using
This mistake can be avoided by placing the phaco chopping phacofracture and phaco chop techniques.
instrument against the nucleus centrally, within the capsulorhexis, J Cataract Refract Surg. 1996 Sep;
and keeping a small amount of posterior pressure against the 22(7):967-9.
nucleus as the chopper is passed peripherally. 6. DeBry P, Olson RJ, Crandall AS. Comparison of energy required for
phaco-chop and divide and conquer phacoemulsification. J Cataract
Incomplete CCC or torn rhexis can extend to periphery and Refract Surg. 1998 May; 24(5):689-92.
towards the poisterior capsule leading to dislocation. Beginners 7. Ram J, Wesendahl TA, Auffarth GU, Apple DJ. Evaluations of in situ
should convert to SICS or ECCE. Zonular dialysis can happen at fracture versus phaco chop techniques. J Cataract Refract Surg.
any stage of nucleotomy. Separation of nucleus with excessive 1998 Nov; 24(11):1464-8.
force with either hand and aggressive rotation of nucleus in
incomplete hydroprocedure are the main causes of dialysis. Pre 8. Joseph J, Wang HS. Phacoemulsification with poorly dilated pupils.
J Cataract Refract Surg. 1993 Jul; 19(4):551-6.
operative conditions which are associated with weak zonules should
be examined thoroughly and surgical technique suitable should 9. Phacoemulsification surgery. Vajpayee RB, Sharma N, Pandey S,
be followed.
Titiyal JS. Jaypee Brothers, Medical Publishers (P) Ltd. New Delhi
Phacoemulsification is the most common surgery and every 2005, and Anshan Publisher UK 2005, 138-154.
surgeon needs to master the technique. Nucleotomy techniques 10. Vanathi M, Vajpayee RB, Tandon R, Titiyal JS, Gupta V. Crater-and-
have evolved to decrease the use of phaco power and faster chop technique for phacoemulsification of hard cataracts. J Cataract
emulsification in the bag. Every case demands special care and Refract Surg. 2001 May; 27(5):659-61.
application of surgeon’s skill for effective completion of 11. Fine IH, Hoffman RS. Phacoemulsification in the presence of
emulsification. Machines with better fluidics, evaluation of cases pseudoexfoliation: challenges and options. J Cataract Refract Surg.
and practice of effective techniques will decrease complication 1997 Mar; 23(2):160-5.
associated with this important step.
References
1. Buratto L. Techniques of phacoemulsification. In: Buratto L, Ed,
Phacoemulsification: Principles and Techniques. Thorofare, NJ, Slack
2003: 295-302.
Author
Jeewan S. Titiyal MD
www.dosonline.org 45
Phaco Chop Techniques – Horizontal vs. Vertical Chop Cataract
David F. Chang MD
Since Kunihiro Nagahara’s original presentation at the 1993 Because the phaco tip is relatively stationary and always remains
ASCRS meeting, several different variations of chopping have in the central 2-3 mm pupillary zone, phaco chop is an excellent
evolved. Conceptually these can be divided into two main technique for small pupil cases.
categories1. I call the classic Nagahara technique horizontal
chopping, because the instrument tips move toward each other in In addition to improved efficiency, the features of reduced phaco
the horizontal plane during the chop. In vertical chopping, the power, reduced zonular stress, decreased reliance on the red reflex,
two instrument tips move towards each other in the vertical plane and the supracapsular location of emulsification all serve to
in order to create the fracture. Although David Dillman later enhance safety. These universal benefits of both horizontal and
popularized the name “Phaco Quick Chop”, Hideharu Fukasaku’s vertical phaco chop are particularly important for complicated
“Phaco Snap and Split” was the first incarnation of this concept. cases – those with brunescent nuclei, white cataracts, loose zonules,
capsulorhexis tears, and small pupils.
All chopping techniques utilize manual instrument forces to
segment the nucleus, thereby replacing the ultrasound power Horizontal Phaco Chop
otherwise needed to sculpt grooves. Such energy efficiency is
possible because the lamellar orientation of the lens fibers creates Following the capsulorhexis and hydrodissection,
natural fracture planes within the hardened nucleus that are hydrodelineation is performed in order to define and separate the
exploited by the chopping maneuver. epinuclear shell. After the endonucleus has been fragmented and
removed, the remaining epinuclear shell will be aspirated and
These smaller nuclear segments are then elevated into the flipped as the final step. In horizontal chop, the chopper tip must
supracapsular space for phaco-assisted aspiration at a safe distance hook the equator of the endonucleus peripherally beneath the
from the posterior capsule. I believe that phaco chop provides the anterior capsule. Several steps and principles facilitate proper
same advantages as supracapsular phaco flip – namely efficiency, placement of the chopper tip.
safety, and reduced stress on the capsular bag without the
difficulty of prolapsing the entire nucleus out of the bag in one There are numerous horizontal chopper designs, but all feature
piece. an elongated tip, which is blunt to avoid capsule perforation. A
relatively long tip is necessary in order to transect thicker,
Classic Nagahara technique is brunescent nuclei, and the inner cutting surface of the tip may be
horizontal chopping, as instrument sharpened for this purpose. I prefer a modified Lieberman
tips move towards each other in horizontal microfinger for horizontal chopping because its slender, curved
plane and in vertical chopping, two tip is ideally shaped for hooking and cupping the lens equator.
Typical right-angled chopper tips do not conform as well to the
instrument tips natural contour of the equator and can result in more distention
move owards each other of the peripheral capsular bag.
in vertical plane The central anterior epinucleus is first aspirated with the phaco
tip. This helps the surgeon to better estimate the size of the
Advantages for Challenging Cases endonucleus, and the amount of separation between the
endonucleus and the capsular bag. The chopper tip touches the
During sculpting, the nucleus is fixated by the capsular bag. In central endonucleus, and maintains contact as it is passed
comparison, chopping applies much less force against the zonules peripherally beneath the capsulorhexis edge (Figure 1a). This
because the phaco tip secures the nucleus, and the manual ensures that the tip stays inside the bag as it descends and hooks
instrument forces are directed centripetally against each other. This the endonucleus peripherally. Because the chopper tip drops into
difference in zonular stress is very evident when chopping and and occupies the epinuclear space, it does not overly distend or
sculpting are compared from the Miyake-Apple viewpoint in stretch the capsular bag fornix. Trypan blue dye improves
cadaver eye surgery. visualization of the capsulorhexis for this step and is a useful
teaching adjunct.
In chopping, the critical instrument maneuvers are primarily
kinesthetic, and are performed with the chopper tip. One does Once it has hooked the nuclear equator, gentle palpating motions
not need the red reflex to visually gauge the depth of the instrument with the chopper can confirm that the tip is internal, and not
tips. This is advantageous when dealing with mature cataracts. external to the capsular bag. Next, the nucleus is deeply impaled
with the phaco tip. The phaco tip should be directed downward
Dr. Chang is a clinical professor of ophthalmology at and positioned as proximally as possible in order to maximize the
The University of California, San Francisco, nuclear mass encompassed between the two instrument tips
and in private practice in Los Altos, CA. (Figure 1b). The chopper tip is pulled directly toward the phaco
tip, and upon contact, the two tips are moved slightly apart (Figure
1c). This separating motion propagates the fracture across the
entire nuclear diameter (Figure 1d).
www.dosonline.org 47
Figure 1: Horizontal chop. (a) The microfinger-shaped horizontal chopper maintains contact with the anterior nuclear surface as it is passed beneath
the capsulorhexis rim in order to hook the nuclear equator. (b) The phaco tip is deeply embedded with a steep angle in order to maximize the amount
of nucleus between the two tips. (c) As the horizontal chop is executed, the chopper must stay deep as it moves directly toward the phaco tip.
(d) Upon contact, the instrument tips are separated sideways to propagate the split.
If the phaco and chopper tips are not kept deep enough, the chop tips are moved apart (Figure 2b-d). Common to all vertical chopper
will not succeed. The thicker and denser the endonucleus, the designs is a short, but sharpened tip that is able to penetrate the
deeper the chopper tip must pass. A tendency to elevate the nucleus. If the chopper tip is too dull, it will displace the fragment
chopper tip during the chop arises from a fear of perforating the from the phaco tip, instead of incising into it.
posterior capsule. Instead of dividing the nucleus, this may merely
score the superficial nuclear surface. Phaco tip should be directed downward
and positioned as proximally as possible
The nucleus is rotated in a clockwise direction, and the same to maximize nuclear mass encompassed
maneuver is repeated in order to create a pie-shaped fragment.
This is elevated out of the bag using high vacuum. Once the first between the two instrument tips.
heminucleus has been chopped and evacuated, there is enough Chopper tip is pulled directly towards
room to pull the second heminucleus to the center of the bag. The phaco tip, and upon contact, two tips are
subsequent chops can then be performed without having to place moved slightly apart. This separating
the chopper beneath the anterior capsule. motion propagates fracture across the
Vertical Phaco Chop entire nuclear diameter.
With denser nuclei, a horizontal chopper must exert a greater The key to a successful vertical chop is to impale the phaco tip as
compressive force in order to fracture the nucleus along its natural deeply into the central nucleus as possible. Like spearing a potato,
lamellar cleavage plane. In contrast, vertical chopping utilizes a it must gain enough of a purchase to be able to lift the entire nucleus
shearing force to split the nucleus into pieces. The vertically upward. By immobilizing the nucleus against the incoming sharp
chopped edges appear sharp - like pieces of broken glass - because chopper tip, enough shearing force is generated to fracture the
there is no crushing force involved. material. High vacuum is invaluable for vertical chop, where a
maximally strong purchase is needed. With brunescent lenses,
Whereas a horizontal chopper moves centripetally inward from burst mode helps to maintain a tight seal around the phaco tip,
the periphery, the vertical chopper is used like a spike to impale which is a prerequisite for accessing high vacuum.
downward into the nucleus just anterior to the centrally buried
phaco tip (Figure 2a). This action creates the fracture line that is
propagated further posteriorly when the embedded instrument
48 DOS Times - Vol. 13, No.1, July 2007
Figure 2: Vertical chop. (a) The phaco tip impales and grips the central nucleus using high vacuum. (b) The sharp-tipped vertical chopper incises
the nucleus just anterior to the phaco tip. (c) The shearing forces extend the crack. (d) Lateral separation of the two instrument tips extends the
crack until the two sections are split apart.
Comparing Chopping Techniques for the softer nucleus. I prefer vertical chopping for brunescent
nuclei since it is more consistently able to fracture through the
In horizontal chop, sequentially removing each newly created leathery posterior plate. However, if mobile brunescent pieces
fragment provides the chopper with increased working space within must be subdivided, horizontal chopping is more effective since
the capsular bag. Because there is no need to hook the equator this maneuver traps and compresses the fragment between the
with vertical chopping, I prefer to fragment the entire nucleus in- two instrument tips.
situ before removing any pieces when employing this method.
Like interlocking puzzle pieces, the adjacent segments add stability Horizontal and vertical chopping are complementary variations
to the portion being chopped. offering different advantages but common benefits. I utilize both
chopping techniques routinely depending on the nuclear density.
Horizontal chopping is suited for With dense lenses, I may employ both strategies during the same
softer nucleus and vertical chopping is case, and I designed the Chang double-ended combination
chopper (Katena) to provide both tips on a single instrument.
preffered for brunescent nuclei
References
Vertical chopping requires that the nucleus be brittle enough to be 1. Chang DF: Converting to Phaco Chop: Why? Which Technique?
snapped in half. Therefore, horizontal chopping is better suited How? Ophthalmic Practice 1999; 17: 202-210.
Author
David F. Chang MD
www.dosonline.org 49
Cortical Irrigation Aspiration Cataract
Shetal M. Raj MS, Abhay R. Vasavada MS, FRCS
The preparatory steps to facilitate thorough cortical aspiration Surgical Technique
are initiated even before performing phacoemulsification. For
ensuring adequate cleavage of the capsule and the cortex, cortical Two paracenteses 1 mm wide are created 3 clock hours apart from
cleaving hydrodissection1 is done in multiple quadrants followed the main incision on either side. After nucleus and epinucleus
by repeated rotation of the nucleus.2 It has been established that emulsification the anterior chamber may be formed with a small
these two procedures work in synergy to accomplish complete amount of dispersive viscoelastic Viscoat (Alcon Laboratories,
cortical aspiration with ease. Multiquadrant cortical cleaving USA), sufficient to allow introduction of the hand pieces without
hydrodissection also facilitates lens substance removal in adult and difficulty. Its excessive injection should be avoided. The bottle
pediatric cataract surgery3,4 by reducing the time of removal as height is reduced to approximately 40 cm before introducing the
well as the fluid volume needed for the procedure. irrigation hand piece to prevent the sudden inflation of the globe
by the fluid gush. The aspiration hand piece is then introduced
Why is thorough Cortical Aspiration Necessary? from the opposite paracentesis. We preset the aspiration flow rate
to 20 to 25 cc/minute and the vacuum to 400 to 650+ mm of Hg.
The Sommering’s ring formation correlates with the quality of If possible, a machine with a linear control should be used for
cortical cleanup.5,6 It can cause pseudophakic pupillary block greater safety. The bottle height is gradually increased to a
glaucoma,7 and the cells within the ring are direct precursors of maximum of 110 cm. during cortex removal. The aspiration
posterior capsule opacification.5,6 A capsular block syndrome8 and process is commenced by moving the aspiration tip close to the
lens particle glaucoma have been observed following residual cortex under the anterior capsule flap. Once the tip is occluded, it
cortex.9 Additionally, with the residual cortical fibers, mitotically is swayed sideways, under the anterior capsule in an attempt to
active lens epithelial cells remain attached. If these are left behind, strip a large area of the cortex. The cortex is stripped from the
they have the propensity to proliferate and migrate towards the periphery to the center. A hemi-quadrant of the distal cortex is
central visual axis leading to visually significant posterior capsule aspirated. Then the irrigation and aspiration hand pieces are
opacification.10,11 Therefore adequate caution should be exercised swapped to aspirate the proximal cortex in the remaining hemi-
to make the reduce the amount of residual lens epithelial cells and quadrant. To minimize the possibility of posterior capsule rupture,
cortical remnants in the capsular bag. the aspiration tip should face anteriorly at all times.
Automated Coaxial or Separate Irrigation or Aspiration? Anterior capsule scrapping, to aspirate the lens epithelial cells, has
proved to reduce anterior capsule opacification or capsular
Advocates of manual irrigation and aspiration (I/A) introduce the phimosis after cataract surgery.14 While scrapping has been
Simcoe’s cannula through a separate paracentesis, 2-3 clock hours effective in reducing fibrotic posterior capsule opacification,15 it
away from the main incision, made sufficiently wide to accommodate has shown no significant difference in another study.16 Our study
the tip, for easy access to sub-incisional cortex. Less fluid is required that was conducted to evaluate the role of scrapping of the anterior
during manual I/A as compared to automated I/A. capsule on anterior capsule opacification showed that the scrapping
was not mandatory with implantation of the AcrySof IOL.
For automated coaxial irrigation and aspiration, modifications in
the ergonomics of the aspiration tip, such as a right angled tip, a J- To stripe the residual cortical fibers lying deep in the fornices of
shaped cannula12 and a steerable silicone tip (Alcon laboratories, the capsular bag or for residual fibers adherent to the central
USA) have been devised for easy access to sub-incisional cortex. posterior capsule, we opt for the Cap Vac mode, wherein the
vacuum and aspiration flow rate are both reduced to 5 mmHg
Automated bimanual (separate) irrigation and aspiration was and 5 cc/min respectively and the bottle height is also reduced to
suggested by Dr. Colvard in 1997.13 We prefer bimanual separate approximately 70-80 cm. With this mode it is safe to turn the tip
irrigation and aspiration (The Buratto bimanual irrigation of the aspiration hand piece posteriorly facing the posterior capsule.
handpiece and aspiration handpiece, textured, Alcon Grieshaber, A moderate chamber depth allows easy negotiation of the tip to
Switzerland) as it allows access to the fornices of the capsular bag the posterior capsule and does not compromise on focusing the
in all clock hours including the sub-incisional quadrants where depth. With short strokes residual cortical fibers and lens epithelial
access to residual cortical matter is difficult and sometimes cells can be scrapped from the posterior capsule. In case of a dense
dangerous because of the close proximity of the aspiration tip to residual plaque, wherein Cap Vac is usually ineffective, an Nd:
the posterior capsule. By introducing irrigation and aspiration YAG procedure may be required post-operatively if the plaque
through different paracenteses the anterior chamber remains well obscures the central visual axis.17
maintained as deformation of the main incision is avoided. This
provides a closed chamber in a true sense and is extremely valuable Special Situations
in collapsible or compliant eyes.
Posterior Polar Cataract
Iladevi Cataract & IOL Research Centre
Raghudeep Eye Clinic, Gurukul Road, Memnagar, In posterior polar cataracts we first perform inside-out
delineation.18 It renders precise demarcation of the nucleus from
AHMEDABAD (Gujarat)
www.dosonline.org 51
the epinucleus. The thick epinucleus provides a precise bowl that pseudophakic human eyes obtained postmortem. Ophthalmology
acts as a mechanical cushion to protect the posterior capsule during 2001;106:505-18.
subsequent maneuvers. The distal epinucleus is stripped off with
the phaco probe, leaving the central area attached until the 6. Schmidbauer JM, Vargas LG, Apple DJ, et al. Evaluation of
peripheral epinucleus is separated.19 The sub-incisional epinucleus neodymium:yttrium – aluminum – garnet capsulotomies in eyes
is mobilized with gentle multiquadrant hydrodissection with a implanted with AcrySof intraocular lenses. Ophthalmology
right angled cannula facing right and left. It is safe to hydrodissect 2002;109:1421-6.
as the capsular bag is not fully occupied. The hydraulic pressure
built-up is not sufficient to rupture the posterior capsule.19 The 7. Kobayashi H, Hirose M, Kobayashi K. Ultrasound biomicroscopic
epinucleus and the cortex are aspirated with separate hand-pieces, analysis of pseudophakic pupillary block glaucoma induced by
taking care to strip only the peripheral cortex in all the quadrants. Soemmering’s ring. Br J Ophthalmol. 2000 Oct;84(10):1142-6.
Once this is accomplished, the central portion, which is abnormally
adherent to the posterior capsule, is lifted only at the end to prevent 8. Baykara M, Erturk H, Ozcetin H. Capsular block syndrome in a
the rupture a thin and vulnerable capsule. In these eyes, if the case with excessive cortical remnants. Ophthalmic Surg Lasers
posterior capsule retains a plaque, we do not scrap it to reduce the Imaging. 2003;34:308-9
possibility of its rupture.
9. Kee C, Lee S. Lens particle glaucoma occurring 15 years after cataract
Zonular Weakness / Dehiscence surgery. Korean J Ophthalmol. 2001;15:137-9.
In instances with a zonular weakness or dehiscence, a capsule 10. Peng Q, Apple DJ, Visessook N, Werner L, Pandey SK, Escobar-
tension ring can be implanted prior to I/A to make the capsular Gomez M, Schoderbek R, Guindi A. Surgical prevention of posterior
bag taut. This keeps the bag stretched and reduces the potential of capsule opacification. Part 2: Enhancement of cortical cleanup by
the bag and especially the posterior capsule being inadvertently focusing on hydrodissection. J Cataract Refract Surg. 2000;
sucked into the aspiration tip. Presence of the ring can prevent 26:188-97.
easy aspiration of the cortex under the anterior capsule
centripetally. Therefore, the aspiration hand piece is swayed in an 11. Vasavada AR, Dholakia SA, Raj SM, Singh R. Effect of cortical
arcuate manner within 3 to 4 clock hours, close to the undersurface cleaving hydrodissection on posterior capsule opacification in
of the cortex before it is aspirated.20 This captures a larger area of age-related nuclear cataract. J Cataract Refract Surg. 2006;
cortex while stripping it from the anterior capsule towards the 32:1196-200.
posterior capsule. As the capsular bag – zonule complex is weak,
this should be done slowly and patiently. 12. Dewey SH. Cortical removal simplified by J-cannula irrigation.
J Cataract Refract Surg. 2002;28:11-4.
Thus, a well controlled anterior chamber environment is necessary
during irrigation and aspiration for a meticulous capsular bag clean 13. Colvard DM. Bimanual technique to manage subincisional cortical
up. material. J Cataract Refract Surg. 1997;23:707-9.
References 14. Hanson RJ, Rubinstein A, Sarangapani S, Benjamin L, Patel CK.
Effect of lens epithelial cell aspiration on postoperative capsulorhexis
1. Fine IH. Cortical cleaving hydrodissection. J Cataract Refract Surg. contraction with the use of the AcrySof intraocular lens: randomized
1992;18:508-12. clinical trial. J Cataract Refract Surg. 2006;32:1621-6.
2. Vasavada AR, Raj SM, Johar K, Nanavaty MA. Effect of 15. Menapace R, Wirtitsch M, Findl O, Buehl W et al. Effect of anterior
hydrodissection alone and hydrodissection combined with rotation capsule polishing on posterior capsule opacification and
on lens epithelial cells: surgical approach for the prevention of neodymium:YAG capsulotomy rates: three-year randomized trial.
posterior capsule opacification. J Cataract Refract Surg. 2006; J Cataract Refract Surg. 2005;31:2067.
32:145-50.
16. Sacu S, Menapace R, Wirtitsch M, Buehl W et al. Effect of anterior
3. Vasavada AR, Singh R, Apple DJ, Trivedi RH, Pandey SK, Werner capsule polishing on fibrotic capsule opacification: three-year
L. Effect of hydrodissection on intraoperative performance: results. J Cataract Refract Surg. 2004;30:2322.
randomized study. J Cataract Refract Surg. 2002;28:1623-8.
17. Vasavada AR, Praveen MR, Jani UD, Shah SK. Preoperative
prediction of posterior capsule plaque in eyes with posterior
subcapsular cataract. Indian J Ophthalmol. 2006;54:169-72.
18. Vasavada AR, Raj SM. Inside-Out delineation. Journal of Cataract
Refract Surgery 2004; 30:1167-1169.
4. Vasavada AR, Trivedi RH, Apple DJ, Ram J, Werner L. Randomized, 19. Vasavada AR, Raj SM. Approaches to a posterior polar cataract.
clinical trial of multiquadrant hydrodissection in pediatric cataract Cataract and Refractive Surgery Today 2005; 72-74.
surgery. Am J Ophthalmol. 2003;135:84-8. 20. Praveen MR, Shah AR, Jani UD, Raj SM, Vasavada AR. Management
5. Apple DJ, Peng Q, Visessook N, et al. Eradication of posterior capsule of congenital bilateral subluxated cataract with Cionni ring.
opacification. Documentation of a marked decrease in ND:YAG Indian J Ophthalmol. 2006;54:39-41.
laser posterior capsulotomy rates noted in an analysis of 5416
Author
Abhay R. Vasavada MS, FRCS
52 DOS Times - Vol. 13, No.1, July 2007
Femtosecond Laser Refractive Surgery
Mahipal S. Sachdev MD, Deepender Chauhan MS, DNB
Laser in situ keratomileusis (LASIK) provides a rapid, stable, The FS30 laser generates 30000 pulses/second, allowing a faster
and accurate correction of ametropia with minimal procedure time, tighter spot placement, and lower overall energy
postoperative pain and is now the most frequently performed exposure than to the FS15 laser (15000 pulses/second). A 60,000
refractive surgery procedure. The most important surgical step in pulse per second upgrade of the IntraLase was introduced in March
LASIK involves the creation of a hinged corneal flap. Until recently, 2006.
the flap has been created with a microkeratome, which relies heavily
on surgical skill and microkeratome precision. Flap-related Laser Technology
complications can delay recovery of visual acuity and may lead to
permanent vision loss. Although modern microkeratomes nearly The femtosecond laser is a mode-locked, diode pump,
always produce high-quality corneal flaps, most beginning, and neodymium-glass laser. It operates in the infrared wavelength
experienced, LASIK surgeons have occasionally created suboptimal range, at 1053 nm. It uses a spot size of less than 3 µm and produces
flaps. There are a wide variety of causes for poor corneal flaps, tissue disruption (Photodisruption) at a specified and precise level
some of which are: within the corneal stroma. The laser produces cavitation bubbles
consisting of water and carbon dioxide which are ultimately
• Unusual anatomic features, such as excessively steep, or flat, absorbed through the corneal endothelium.
corneas
A unique feature of the femtosecond laser is its ability to produce
• Inadequate patient cooperation, with head movement or lid tissue disruption at very low energy settings. This is due to the
squeezing very short pulse width, or pulse duration, associated with the laser
(600 to 800 fs), and to the very rapid pulse repetition, or speed, of
• Deep-set eyes the laser (15,000 to 60,000 pulses per second). Because
power=energy/time, femtosecond pulses allow energy settings to
• Prominent brows be low, yet retain high peak power. Consequently, postoperative
inflammation can be reduced, especially when pulse repetitions
• Narrow palpebral fissures become faster.
• Inadequate suction The increased speed of the laser decreases suction time for
enhanced safety and patient comfort and decreases the time of
• Microkeratome malfunction the procedure. Tighter spot placement produces better dissection
quality and a smoother corneal interface and facilitates flap
• Defective microkeratome blade elevation.
• Unexplained causes.
Although the incidence of poor flaps is low, the ramifications of a Uses of the Femtosecond Laser
poor microkeratome flap may be severe. Some LASIK surgeons
have reverted to surface ablation (photorefractive keratectomy, There are several uses for the femtosecond laser, and these uses
laser-assisted epithelial keratomileusis, and epithelial laser-assisted are expanding as surgeons gain more experience with this versatile
keratomileusis), to avoid even the rare flap complication that might device. The laser can be used for
occur. However, surface ablation techniques are associated with
slow visual recovery and significant postoperative discomfort. Any • Creating corneal flaps for LASIK
technology which improves the safety and precision of creating a
corneal flap, will, no doubt, be of great interest to LASIK surgeons. • Lamellar keratoplasty
This may explain the rapid growth in the use of the IntraLase
femtosecond laser. IntraLase is said to have captured 25% of the • Creating a channel for INTACS
market in a short time, so, it seems that, despite the great expense
of a second laser, LASIK surgeons find the safety considerations • Penetrating keratoplasty.
of a laser-created corneal flap to be compelling.
In 1992, Lai used a titanium sapphire femtosecond laser to create
lamellar and penetrating corneal incisions, as well as LASIK flaps
in porcine eyes. Femtosecond laser ablation for LASIK flap creation
(intra-LASIK) was introduced in late 2001 and is growing rapidly
in use. Intra-LASIK entered its second generation with the
introduction of the IntraLase FS30 femtosecond laser (IntraLase
Corp.), which replaced the IntraLase FS15 femtosecond laser1.
Centre For Sight, Figure1. Principle of IntraLase: Creation of a cleavage plane using
B5/24, Safdarjung Enclave, photodisruption.
New Delhi-110029
www.dosonline.org 57
Table 3. Comparison microkeratome Vs Intralase
Microkeratome Intralase
Flaps Lenticular Planar
Bed Truncated 360 degrees
Side cut Beveled More vertical (can be
customized to desired angle)
Figure 2. Firing of Femtosecond laser in a Raster pattern Bed Wet Dry
to create corneal flap.
and a desired hinge angle can be made. Intralase has also been
Table 1. Advantage of flaps produced by Femtosecond Laser used successfully in patients who have undergone RK9, however,
• Greater accuracy of flap creation the flap thickness in such patients should be 140 microns or more.
• Thin yet stable flaps
• Fewer flap complications Advantage of Femtosecond Laser Flaps
• Better centration
• Stronger flap adherence Compared with the microkeratome, Femtosecond Laser has
• Less IOP rise during suction several distinct advantages4,7,9,10, as a tool for making LASIK flaps.
• Fewer high order aberrations
• Less dry eyes Femtosecond Laser flaps are more accurate than microkeratome
• Less epithelial ingrowth flaps, in both thickness and diameter. Because of their accuracy,
• Better contrast sensitivity5 and their uniform thickness throughout, Femtosecond Laser flaps
• Reduced high order aberrations6 are not associated with buttonholes, or undesirable thinness.
Table 2. Possible disadvantages of flaps produced by Microkeratome flaps are highly dependent on anatomic factors,
Femtosecond Laser particular corneal curvature. Femtosecond Laser flaps are uniform,
• Suction breaks despite anatomic variability, and their dimensions accurately reflect
• Incomplete flaps the settings selected by the user.
• Transient light sensitivity11
• Persistent bubbles – stroma / anterior chamber12 Microkeratome flaps are generally designed to be 160 to 180 µm
• Harder to lift flaps in thickness. It is possible to create thinner (yet stable) flaps
• Granular bed with the Femtosecond Laser. There flaps are designed to be 90 to
120 µm.
Despite their thinness, Femtosecond Laser flaps are remarkably
sturdy, and do not seem to be particularly subject to tearing.
Flap Creation Centration is better, and easier to achieve with the Femtosecond
Laser than with the microkeratome. There is no “skating” of the
Patient interface comprises of suction ring and an applanating Femtosecond Laser suction ring, as opposed to the microkeratome
glass plate. The laser treatment is delivered through a round, flat, suction ring, and once suction is achieved, small adjustments in
glass plate on the end of a removable cone , which is attached to centration can be made with the computer mouse.
the laser. The cone “docks” with a low-pressure suction ring
attached to the eye, and centered on the pupil. There is less elevation of intraocular pressure with the
Femtosecond Laser suction ring. Instead of raising pressure to 60
To create the corneal flaps, the spots can be placed in any of the 2 or 70 mm Hg with the microkeratome, the Femtosecond Laser
patterns: a raster pattern, in which the spots travel back and forth typically raises pressure to about 35 mm Hg. This provides an
in horizontal lines; or a spiral pattern, in which the spots start extra margin of safety when performing LASIK in patients with
centrally, and spiral out to the periphery. Thousands of laser spots, glaucoma or retinal problems.
is released from the eye, and the laser is elevated out of the way.
Femtosecond Laser flaps have better adherence to underlying
Under the excimer microscope, the corneal flap is dissected by stroma, and are less likely to be displaced by trauma than
inserting an instrument through the side cut, and sweeping microkeratome flaps.
through the bed away from the hinge. Once the flap is lifted, the
surgeon will note that the bed is dry, and somewhat granular in Creation of flap by Femtosecond Laser leaves behind a drier
appearance. Sometimes, small bubbles persist in the anterior stroma, thus making the procedure more predictable.
stroma. Once the excimer ablation has been completed, the corneal
flap can be easily repositioned. Compared to flaps of similar dimensions prepared by mechanical
microkeratomes, Femtosecond Laser provides a larger surface
The IntraLase is highly versatile, and different flap dimensions area for ablation. This is achieved by a small hinge angle.
can be set . Although flaps as thin as 90 µm can be easily prepared
with Intralase, 120±10 µm thick flap is prepared most often. Studies Although Femtosecond Laser flaps are more difficult to lift than
have shown that the standard deviation of flap thickness is as low microkeratome flaps, the advantage of a stronger adhesion, and
as 14 microns. The flap diameter is typically set to about 9.0 mm. greater resistance to trauma, is probably, on balance, an
Femtosecond Laser advantage.
58 DOS Times - Vol. 13, No.1, July 2007
Figure3. Creation of intrastromal grooves for implantation of Bubbles may persist for several minutes after creating the lamellar
intrastromal corneal rings. bed with the Femtosecond Laser12. These bubbles may interfere
with the surgeon’s view, or with the excimer laser tracking devices.
In early studies, diffuse intralamellar keratitis (DLK) occurred in However, persistent bubbles do not seem to interfere with delivery
up to 20% of Femtosecond Laser FS15. Currently, DLK, is a very of effective excimer laser treatment to the corneal bed, and one
rare complication of Femtosecond Laser FS 60KHz LASIK. does not need to delay treatment until all the bubbles have been
absorbed. Occasionally, bubbles can migrate into the anterior
Clinical and confocal microscopy findings2 comparing chamber, but again, this does not seem to interfere with the success
Femtosecond Laser flaps and microkeratomes have shown that of the LASIK procedure.
the Femtosecond Laser provides a more reproducible flap thickness
and fewer interface particles than previously observed using Interfaces are slightly granular in appearance after Femtosecond
microkeratomes. Laser procedures, and generally, crystal clear after microkeratome
flap. Despite the appearance, postoperative visual acuities after
Other possible advantages may include: fewer higher order both procedures are comparable.
aberrations, less postoperative astigmatism, better contrast
sensitivity, less epithelial ingrowth, lower enhancement rates, and Complications
less dry eye. Because these postoperative consequences of LASIK
are subtle, or uncommon, further studies are needed to provide Suction break & Incomplete Flap
convincing evidence that they indicate a real advantage for the
Femtosecond Laser procedure. The most common complication during the creation of
Femtosecond Laser corneal flaps is the suction break. Loss of
Disadvantages of Femtosecond Laser suction can occur with improper positioning of the suction ring on
the eye, with entrapment of lashes or edematous conjunctiva
Creating the flap takes longer with the Femtosecond Laser than with beneath the ring, or with squeezing, or a tight orbit. This can result
the microkeratome. An Femtosecond Laser flap requires 59 seconds in incomplete flaps, either at raster stage or during side cut. If the
with the 15 kHz software, and 39 seconds with the 30 kHz software. lamellar bed treatment has been completed, the Femtosecond
The newer 60 kHz version has decreased the flap creation time to 18 Laser can be set for a side cut treatment only, and the procedure
seconds, close to the time required for a microkeratome pass. can be completed immediately. If the suction break occurs while
making the side cut, it is preferable not to attempt to lift the flap,
Femtosecond Laser flaps are more difficult to lift during but rather to retreat at a later time, and make a smaller diameter
retreatment, than microkeratome flaps. The stronger adherence flap (0.5 mm smaller in diameter and 40 microns deeper). Another
is, due to inflammation created by the femtosecond laser energy. possibility is to treat such cases with surface ablation.
This inflammatory reaction is lacking with a microkeratome cut.
Transient light sensitivity
Some Femtosecond Laser procedures are associated with more
postoperative inflammation than microkeratome procedures. The A small subset of patients develop significant corneal haze, which
energy delivered by the femtosecond laser can be considerable, may be associated with transient light sensitivity; the underlying
and surgeons have found it advantageous to reduce the energy of cause of which has been attributed to keratocyte activation and
the bed, and especially, the side cut settings, to minimize appears to be linked to use of higher raster energies11. Transient
postoperative inflammation. The low side cut energy is particularly light sensitivity, is a peculiar occurrence of photophobia 1 to 3
important in influencing inflammation. Because the side cut is months after uneventful Femtosecond Laser treatment. Transient
close the limbus, low side cut energy is desirable to keep light sensitivity is amenable to treatment with corticosteroids, and
inflammation minimal. If the side cut energy is lowered too much, it may represent inflammation of the ciliary body.
it will be harder to enter the wound with a dissecting instrument.
In addition, if the bed energy setting is too low, it will be difficult to The response of corneal keratocytes is less when lower raster and
lift the corneal flap. side cut energies are used. Compared with the FS15, there is an
apparent reduction in overall interface reflectivity and fewer
The increased cost of adding another laser can be considered a interface particles with the FS60 laser. The raster energy used for
disadvantage to a laser center, or to a patient who must pay a FS15 is typcally between 1.9 to 2.0 µJ (raster line separation 9 µm,
higher procedure fee. raster spot separation 9 to 10 µm), while the raster energy used
for FS30 is 1.2 µJ on average (raster line separation 8 µm, raster
spot separation 8 µm). In addition, the FS30 laser uses a smaller
step size in the raster pattern and thus create a smoother surface
with less backscattering of light. All these advantages are further
magnified with the introduction of FS60KHz.
Use of Femto Second Laser in PK
The availability of high-precision, programmable femtosecond
lasers greatly simplifies and improves the preparation shaped
corneal tissue for PK3. By fashioning a donor button with a shaped
edge, a larger area of surface contact between the donor graft and
the host can be created. This approach helps reducing
postoperative astigmatism and allows earlier suture removal
www.dosonline.org 59
The words you are searching are inside this book. To get more targeted content, please make full-text search by clicking here.
DOS_July_2007
Discover the best professional documents and content resources in AnyFlip Document Base.
Search