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What capsulotomy size is best for femtosecond laser cataract surgery?
Quentin B. Allen, MD, takes a customized approach, while Keith A. Walter, MD, prefers a smaller capsulotomy.
Welcome to another edition of CEDARS/ASPENS Debates. CEDARS/ASPENS is a joint society of cornea, cataract and refractive surgery specialists, here to discuss some of the latest hot topics in ophthalmology.
Femtosecond laser use for cataract surgery continues to grow. With this new technology, we now have the ability to modify our surgical techniques with precision never before thought possible. One of the variables that we now can modify is capsulotomy size. While we can adjust the size in increments of one-tenth of 1 mm, it is not clear what size is best. This month, Quentin B. Allen, MD, and Keith A. Walter, MD, discuss their preferences and techniques for selecting capsulotomy size. We hope you enjoy the discussion.
Kenneth A. Beckman, MD, FACSOSN CEDARS/ASPENS Debates Editor
One size does not fit all
Once the decision has been made to employ femtosecond laser technology for cataract surgery, a surgeon is faced with seemingly endless options for surgical plan customization, including corneal incision and arcuate placement and depth, lens fragmentation patterns, power variance, and capsulotomy centration and size. Assuming the corneal and lens settings have been determined, surgeons are left with a choice regarding capsulotomy size: utilize a consistent size across all lens and patient types, or alter the capsulotomy size depending on various clinical factors. I would advocate for a custom approach, with individualization of the capsulotomy power and size depending on various clinical scenarios, which I will discuss.
In discussions with colleagues, it has become apparent that some surgeons utilize a fairly consistent small capsulotomy size, usually between 4.8 mm to 5 mm. There is evidence to suggest that there is increased refractive predictability with femtosecond laser, likely due to capsular overlap of the IOL, which a smaller capsulotomy does help to ensure. There are cases in which a smaller capsulotomy would be ideal, for instance when implanting an IOL with a smaller optic such as the Crystalens or Trulign accommodating lenses (both Bausch + Lomb). In fact, for Crystalens and Trulign cases, my capsulotomy size is typically 4.8 mm to 5 mm, with implantation of a capsular tension ring to prevent capsular phimosis (another controversial topic). However, is such a small capsulotomy necessary, or even desirable, for other IOL types and other clinical scenarios? I don’t think it is.
When should one consider a larger capsulotomy, and when is the capsulotomy too big? The most obvious case in which a larger capsulotomy might be desirable is when the surgeon is more likely to employ a supracapsular lens disassembly technique such as phaco tilt or phaco flip. These techniques reduce zonular stress by eliminating the need for lens rotation. This is potentially advantageous in cases of compromised zonular support such as pseudoexfoliation, or when more intraoperative manipulation is anticipated, as in the case of a mature cataract. Some surgeons may not mind working within the confines of a smaller capsulotomy, but why make things more difficult than they have to be in an already challenging case? In my experience, a smaller capsulotomy may make supracapsular approaches more challenging. Achieving a consistent and complete fluid wave during hydrodissection is more difficult and potentially more risky with a small capsulotomy because there is more distance for the fluid wave to travel to the lens equator and therefore more forceful hydrodissection may be required to elevate the lens. In this scenario, there may also be a higher risk for fluid becoming trapped behind the lens and a capsular rupture may be precipitated. This risk is compounded in the case of a mature cataract, where the capsule is taut and already under increased intralenticular pressure. This would therefore be another clinical scenario in which a larger capsulotomy may be indicated.
One may also consider customizing the size of the capsulotomy in the event of encountering some degree of ocular tilt during femtosecond docking. The auto-centration feature available on most lasers cannot completely correct for variance in tilt that may be encountered during docking. The end result is less than optimal centration of the capsulotomy in this scenario, where a larger capsulotomy size may lead to asymmetric overlap of the capsule edge onto the IOL. This may potentially affect refractive predictability by altering effective lens position or inducing IOL tilt. Therefore, it is prudent to either re-dock in the case of significant tilt, or if this is impractical or impossible, the capsulotomy size may be reduced to increase the likelihood of maintaining anterior capsule/IOL overlap in the event of a slightly decentered capsulotomy. I do not advise reducing the capsulotomy size to less than 4.5 mm, as the risk of inadvertent damage to the anterior capsular rim may be increased and the ability to manipulate the cataractous lens may be reduced, especially in the event of a dense cataract. When necessary, corneal arcuate incisions may be placed with the laser, and the capsulotomy and lens fragmentation done manually, rather than risk placing a tiny capsulotomy that may limit lens disassembly options or increase risk of radial tears during phaco. Some surgeons may be comfortable working within the confines of a very small capsulotomy, but after initially performing many cases like this in the first year or two of having a femtosecond laser, I now prefer to be comfortable and less stressed during cataract surgery. As they say, there is no extra credit in cataract surgery for degree of difficulty.
So what is the typical adjustment factor for femtosecond laser depending on the clinical scenario?
My standard capsulotomy size is 4.9 mm to 5.1 mm, depending on docking tilt, lens density and IOL type. I tend to err on the side of smaller capsulotomy size for multifocal lenses to ensure centration and capsule overlap. I will increase from 5.2 mm up to 5.5 mm (some surgeons go as high as 6 mm) for very dense lenses (3+ to 4+ nuclear sclerosis and higher). Mathematically, when going from a 4.9 mm capsulotomy to a 5.5 mm, there is 26% more area within which to perform maneuvers. This extra room to work without worrying about inadvertently violating the anterior capsular rim has definite benefits. Obviously, refractive predictability may suffer if a very large capsulotomy is employed, as the lens may tilt or shift to a more anterior effective lens position as capsular fibrosis and contraction occur. However, in cases that are already very high risk, some refractive instability is a reasonable trade-off to avoid capsular tears and possible sulcus or anterior chamber IOL placement. In the event of a posterior capsular tear, a 5.5-mm capsulotomy provides more than adequate capsular support for a sulcus-fixated IOL, although reverse optic capture is less likely through the larger capsulotomy. Fortunately, with modulating the femtosecond laser capsulotomy size depending on the clinical scenario, this situation is rarely encountered. With advancements in technology, surgeons should consider adjusting capsulotomy size as a part of customizing all aspects of the surgical plan, in a tailored approach, to each patient’s unique anatomy and visual needs.
- Reference:
- Toto L, et al. J Refract Surg. 2015;doi:10.3928/1081597x-20150727-02.
- For more information:
- Quentin B. Allen, MD, can be reached at Florida Vision Institute, 1050 SE Monterey Road, Suite 104, Stuart, FL 34994; email: q_allen@yahoo.com.
Disclosure: Allen reports he is a consultant to Alcon and Valeant.
Smaller capsulotomy is better
In today’s “supersize” society, almost everything that is bigger is better. There are a few exceptions, however, and laser capsulotomy is one of them. Before you take this to an extreme, I am not talking about a 1-mm diameter capsulotomy. What I am talking about is a smaller capsulotomy than you are normally used to doing. I will now detail for you the reasons why I believe this to be true.
First of all, I would like to clearly state that I have done larger capsulotomies in my career, and when I first started doing femtosecond laser capsulotomies, I used a 5.2-mm size, which was smaller than I was doing with my manual technique. I was immediately impressed with the performance of the Catalys platform (Johnson & Johnson Vision), making a perfectly round capsule, exactly where I intended in the center of the lens capsule. What I soon realized was that the optic edge was not always covered either at all or not as much as I would prefer. This brings me to the first reason why you should do a smaller capsulotomy, optic edge coverage. I am a big believer that if you wish to reduce postop day 1 complaints of dysphotopsias, you should make sure your capsule is smaller than the diameter of your lens, and you should rotate your lens so that the haptic-optic junction is at 3:30 and 9:30. You do those two things and you will stop needing to dilate your patients on the first day or answer questions about flashing lights.
Like I said, I like my edge covered up by the capsule, but with 5.2 mm it often was not enough. How could this be when my optic is 5.5 mm? For those of you not using the Catalys, you may not realize that the femto-ablated capsule is more flexible and it can stretch a bit bigger without breaking. I have even hooked the capsule with a Malyugin ring (MicroSurgical Technology) numerous times without breaking or tearing it. I think the stretching in size was from prolapsing the lens and doing a supranuclear technique. So eventually, I went down to 5 mm, and while that was better, it was not always enough. Now I am at 4.8 mm and have stuck with that for the last 3 years.
I always get perfect optic edge coverage with no lenses wanting to slip out of the bag or becoming captured with the optic in the sulcus. With the scan capsule feature on the Catalys, I ensure proper optical axis centration, and I have an even amount of coverage 360° around my well-centered lens.
I am not big on cleaning/polishing the posterior capsule or underneath the anterior capsule. I simply do not have time for that, and I fear breaking the capsule trying to be a hero. Besides, what is wrong with doing a YAG capsulotomy later? Better to be a coward and operate another day, I suppose. When my academic partner, who loves to meticulously polish the capsule, found out I was doing a small 4.8-mm capsule, he immediately predicted (as many of you are right now) that I would have an epidemic of capsular phimosis. I am happy to report that I have only had two cases of phimosis in my first 1,000 cases of femtosecond cataract surgery. I think that is acceptable.
You may be asking, is it hard to operate through such a small opening? What kind of wizard skills do you have? It is really not hard at all. In fact, with smaller pupils, I will often do even smaller capsulotomies than 4.8 mm, when the software prompts me that my planned size might intersect with the iris based on the real-time OCT. What is the smallest I have allowed? So far, 3.2 mm, and you guessed it, not that difficult and no radial tears or postop phimosis.
- For more information:
- Keith A. Walter, MD, can be reached at Wake Forest University Eye Center, 4030 Windsor Place Drive, Winston-Salem, NC 27106; email: kwalter@wfubmc.edu.
Disclosure: Walter reports he is a consultant and speaker for Johnson & Johnson.