At Issue: Small-incision cataract surgery

At Issue posed the following questions to a panel of experts: “What technology holds the most promise for smaller-incision cataract surgery, and why?”

PRISCILLA P. ARNOLD, MD
IOL design

	Priscilla P. Arnold

It is interesting to consider this question. In the 1970s and early 1980s, phacoemulsification was accepted because reliable capsule-fixation implants became available. Overwhelming popularity of phacoemulsification, however, did not occur until foldable, small-incision implants were developed. In other words, the small-incision implant drove the widespread adoption of an existing technology. Now “routine” phaco incisions are generally 2.5 to 3 mm in size. What would be the advantage of an even smaller incision size? I believe there are three possible answers to that question:

1. Greater control of the internal ocular environment.
2. Reduction of the already tight astigmatic control.
3. Decreased incidence of endophthalmitis. (Recent studies make the increasing incidence with clear-corneal incisions hard to refute.)

With that in mind, I believe the technology that holds the most promise is a coaxial small-incision system. It is the technique with which most surgeons are already familiar and has stood the test of time in terms of safety and efficacy. However, I do not believe any ultra-small system will be widely adopted until there is reason to make this transition due to IOLs that are implanted in such 2 mm or less incisions. These are just beginning to come into use. In other words, I think the IOL design will once again drive the utilization of the small-incision technology.

For more information:

• Priscilla P. Arnold, MD, can be reached at 1011 E. Montclair St., Springfield, MO 65807; 417-890-8877; fax: 417-890-7747; e-mail: ppa@arnoldvision.com.

STEVE A. ARSHINOFF, MD, FRCSC
Torsional, continuously variable pulsed axial phaco

	Steve A. Arshinoff

Phaco achieved much of its original popularity due to its promise of smaller incisions than ECCE. Foldable IOLs then took us from 6 mm to 3 mm with the inherent advantages of astigmatism control and the potential to perform real lens-based refractive surgery. Even smaller incisions should enhance refractive results, quicken postoperative rehabilitation and reduce the risk of postoperative endophthalmitis.

Biaxial sleeveless surgery potentially yields smaller incisions and enhanced access to subincisional cortex but suffers from reduced chamber control (because of increased wound leakage), increased wound damage compared to sleeved surgery and loss of maneuverability of the second instrument due to its increased size. Referring to it as microincisional cataract surgery is good advertising but a misnomer.

The advent of sub-2-mm coaxial surgery retains all the advantages of coaxial sleeved surgery— enhanced chamber stability, reduced wound damage and increased maneuverability of the second instrument— and it additionally offers new innovative power modulations that greatly facilitate and reduce the risks of surgery. Torsional phaco is wonderful for all but grade 4 cataracts. It eliminates chatter, which consumes up to 75% of the energy used in traditional axial phaco. It can be combined with continuously variable pulsed axial phaco, which simply shortens each phaco pulse as its power is increased with foot pedal depression, to reduce chatter. The combination of torsional with continuously variable pulsed axial phaco in various preprogrammed algorithms allows phaco of any density nucleus with greatly reduced effort, less fluid consumption, less anterior chamber turbulence and less input energy. The computer continually varies power modulations as the foot pedal descends for harder lenses to lens-density-appropriate settings. Adding continuously variable pulsed axial phaco enables torsional phaco to work for even the most dense lenses, and the allowable settings are almost infinite to accommodate surgeon preferences and practice types. I have enjoyed great success with this technology and find it hard to believe I survived without it before.

For more information:

• Steve A. Arshinoff, MD, FRCSC, can be reached at 2115 Finch Ave. West, Suite 316, Toronto, Ontario M3N 2V6, Canada; 416-745-6969; fax: 416-745-6724; e-mail: saaeyes@idirect.com.

Reference:

• Arshinoff SA. Biaxial phacoemulsification. J Cataract Refract Surg. 2005;31(4):646.

DAVID F. CHANG, MD
Minor differences in incision size

	David F. Chang

We already have excellent phaco instrumentation and techniques for removing cataracts through smaller incisions. Bimanual microincisional phaco is certainly a viable technique that offers both advantages and disadvantages compared to coaxial phaco. Micro-coaxial phaco achieves a smaller incision with virtually no change in technique. Both of these strategies utilize hyperpulse power modulations rather than non-ultrasonic energy sources.

The main issues are 1) is there a significant advantage to reducing incision size below the typical 3-mm opening that most current foldable IOLs can be inserted through, and 2) if it is important to further downsize incisions, how can we get IOLs through them?

At one time the quest for smaller incisions drove us to adopt foldable IOLs. However, from now on we will select IOLs because of their optical advantages rather than their incision size profile. Differences between a 3-mm and a 1.5-mm incision would have short-term consequences at best. (There is no evidence that endophthalmitis rates are any different, but if they were, tissue glue could make such theoretical differences moot.) Optical differences (asphericity, wavefront matching, toricity, presbyopia correction, adjustability) are life-long. For these reasons, minor differences in incision size will no longer be a major factor in IOL selection.

For more information:

• David F. Chang, MD, can be reached at 762 Altos Oaks Drive, Suite 1, Los Altos, CA 94024; 650-948-9123; fax: 650-948-0563; e-mail: dceye@earthlink.net.

UDAY DEVGAN, MD, FACS
Fluidics

	Uday Devgan

The true challenge of smaller-incision cataract surgery is not the IOL as is commonly believed — it is fluidics.

Certainly, the technology to produce an ideal IOL that has all of the currently desired properties (excellent aspheric optics, low PCO rate, good biocompatibility, low dysphotopsia rate) as well as the ability to go through a small, sub-2-mm incision is near. IOLs that do not have all of the desired properties but instead tout a small incision as their only attribute have not done well in other countries and will not likely do well here in the United States.

The true challenge of smaller-incision cataract surgery is fluidics. We have already embraced the use of advanced phaco power modulations to dramatically reduce phaco energy and heat, and the ability to do sleeveless phaco exists on many platforms. The difficulty is balancing the fluidics as we make progressively smaller incisions. Due to Poiseuille’s equation that governs fluidics, the flow rate varies exponentially as the radius of the tubing/needle to the fourth power.

There is a balance where making a progressively smaller incision gives minimal additional astigmatic benefit while negatively affecting fluidics and efficiency. I feel that currently this level is 2 mm for micro-coaxial sleeved phaco or two 1.5 mm incisions for split-infusion sleeveless bimanual microincision phaco, with both systems using a 0.9 mm phaco needle.

This level of small-incision surgery with stable fluidics, using a 2-mm coaxial or two 1.5-mm bimanual incisions, is available today with current phaco platforms. For us to achieve even smaller incisions in the future will likely require forced inflow (instead of the current gravity-based systems) and reworked fluidics.

For more information:

• Uday Devgan, MD, FACS, is an assistant clinical professor at the Jules Stein Eye Institute at the University of California, Los Angeles, chief of ophthalmology at Olive View-UCLA Medical Center, and in private practice in Los Angeles and Sun Valley, Calif. He can be reached at 9375 San Fernando Road, Sun Valley, CA 91352; 818-768-3000; fax: 818-504-4463; e-mail: devgan@ucla.edu.

RANDALL J. OLSON, MD
Hydrophilic acrylic lenses

	Randall J. Olson

An answer to this question first requires stating where we are and then talking about where we will be going. Microphaco, at the present time, can allow cataract surgery through incisions even smaller than 1 mm; however, the IOL technology has lagged behind this incision size capability. While some lenses have been proposed and used for these small incisions, it would appear that development, and in particular U.S. regulatory approval process testing, has not resulted in much movement in this area at this time.

The significant breakthrough in moving below the usual 2.8 mm to 3 mm has been the micro-coaxial development by Alcon, which with its new insertion system on the SA-60 lens is taking overall incision size down to close to 2 mm. This would, therefore, appear to be the state-of-the-art small-incision size at this time in regard to what is generally available.

It would be difficult to move below 2 mm without going to a microphaco system in which the aspiration/cutting instrument is separated from the irrigation instrument. Good studies show that sub-1-mm microphaco, indeed, is efficacious; however, finding lenses that do as well as lenses we have today to take advantage of those incisions has proven to be a more daunting task. It would appear that hydrophilic acrylic, due to the elasticity that can be engineered into this material, may become important in bridging this gap. There are hydrophilic acrylic lenses that take the barrier down to a 1.5-mm incision, and I know Bausch & Lomb is working on a full 6-mm optic IOL with truncated edges that for most lower diopters will go through an incision that measures 1.5 mm or less after insertion. It would appear, therefore, that lenses such as this that give us our full quality 6-mm optic with truncated edges could become the next state of the art.

This all presupposes that moving below 2 mm is clinically important. While evidence that moving from a 3-mm to a 2-2.2-mm incision potentially produces a more stable wound with less astigmatism shift has been proposed, diminishing return is clearly going to come into play where smaller incision sizes may not have clinically important wound stability or refractive stability advantages. Having stated this, it is important to continue to push the envelope because it is only by doing this in a safe way that we will have studies to find the point where decreasing size is probably unimportant.

The most important breakthrough would be a lens that is injectable. There are important groups working on this. One group we are aware of is Calhoun Vision with its adjustable lens in an injectable format. The work of Dr. Nishi with a lens that fills the entire capsular bag, thereby eliminating any dysphotopsia, and yet is still adjustable, is another possibility further down the road. This would presuppose elimination of after-cataract issues, which indeed may be possible through innovative new technology such as the Milvella PerfectCapsule device.

So stay tuned. I think we are still in for some interesting major advancements in this field in the future.

For more information:

• Randall J. Olson, MD, can be reached at John Moran Eye Center, 50 N. Medical Drive, Salt Lake City, UT 84132; 801-585-6622; fax: 801-581-8703; e-mail: randall.olson@hsc.utah.edu.

R. BRUCE WALLACE III, MD, FACS
Dependable microincision IOLs

	R. Bruce Wallace III

Dependable microincision IOLs will likely be the biggest driver to convince surgeons to transition to smaller-incision phaco. Unfortunately, current lens designs (primarily available in Europe) have been found to be relatively unstable, and many surgeons have abandoned them. Bimanual phaco methods still make the most sense, but there have been problems with aspiration overcoming the present gravity infusion. With the increased interest in refractive IOLs, what patients are really looking for is better uncorrected multifocal vision. They frankly do not know what size incision they receive and because most of our 2.8-mm incisions are unlikely to induce problem cylinder at this time, we have been satisfied to continue using 2.8-mm phaco incisions until a satisfactory microincision multifocal IOL is available.

For more information:

• R. Bruce Wallace, III, MD, FACS, can be reached at 4110 Parliament Drive, Alexandria, LA 71303; 318-448-4488; fax: 318-448-9731; e-mail: rbw123@aol.com.