Is it time for microincision cataract surgery?

In an ASCRS survey, 20% of surgeons said they plan to adopt bimanual MICS this year. But some ask why do it now, before ultrathin IOLs are available?

Opinion is divided over the value of adopting bimanual microincision phacoemulsification before the approval of IOLs that fit through the ultrasmall incisions. Leading cataract surgeons agree that a microincision technique is probably the future of cataract surgery, but they disagree over whether now is the time to adopt the technique.

When microincision lenses that match the standards set by modern foldable IOLs become available in the United States, microincision cataract surgery (MICS) will likely become the preferred cataract procedure, Ocular Surgery News editorial board members interviewed for this article said.

“Once we have IOLs that fit through 1.5-mm to 2-mm incisions, surgeons will probably transition to microincision phacoemulsification as their procedure of choice,” Richard L. Lindstrom, MD, of Minnesota Eye Consultants in Minneapolis, said. “For cataract surgeons, it’s the technique of the future.”

“Microphacoemulsification is absolutely inevitable. Without question, it is part of the evolution of cataract surgery,” agreed Robert H. Osher, MD, of the Cincinnati Eye Institute. “Just as we saw cataract surgery go from 12 mm to 10 mm, from 10 mm to 6 mm and from 6 mm to 3 mm and then to 2.75 mm, we will always want to find the smaller, less invasive way to disturb tissue.”

Richard Packard, MD, FRCS, FRCOphth, who currently performs bimanual MICS in 20% to 30% of his cataract cases at The Prince Charles Eye Unit in Berkshire, England, said that the “change to microincision phaco is very likely,” but not before microincision lenses are proven to measure up to currently available foldable IOLs.

Surgeons interviewed for this article shared the opinion that microincision IOLs still face at least 5 years of clinical study before they achieve U.S. regulatory approval.

In the meantime, I. Howard Fine, MD, of Drs. Fine, Hoffman and Packer in Eugene, Ore., advised surgeons not to hesitate. The time to incorporate bimanual MICS into practice is now, he said.

“Bimanual microincision phaco is a better operation, a better way to remove a cataract. Surgeons should get a head start for their practice and their patients,” Dr. Fine said.

Not all agree with that assessment. Dr. Osher cautioned surgeons not to “jump on the bandwagon because vocal leaders are raving about microphaco.”

“My efficiency is less and the early postoperative results are not as good as coaxial phaco in my hands,” Dr. Osher continued. “Moreover, until we have a high-quality smaller lens that has a low posterior capsular opacification rate, high-quality optics, the potential to provide correction of presbyopia, astigmatism and other aberrations, and macular protection, surgeons shouldn’t feel like they are missing out.”

Ocular Surgery News explored the advantages and disadvantages of adopting a MICS technique now or waiting until later in a series of interviews with these leading cataract surgeons.

Advantages to MICS

Dr. Fine sees no reason to wait. He said bimanual MICS is as close to an “ideal procedure” as possible.

“We have nearly a completely closed system during bimanual phaco, much more than in coaxial phaco,” Dr. Fine said. “The fluidics are better because fluid is entering through one side of the eye and exiting through the other side. There are no competing currents around the phaco tip.”

Dr. Fine said nuclear fragments are more accessible to the microincision phaco tip because the space around the tip is free of traveling fluid that might deter material from the tip. This allows greater stability in the anterior chamber.

“It’s nice to be able to move the phaco tip for extraction of lens material independent of the incoming stream of fluid. We like it better,” Dr. Fine said, noting that the surgeons he practices with now use the bimanual MICS technique routinely for cataract surgery.

“It’s just a better procedure,” he said.

In a study comparing bimanual MICS to standard coaxial phacoemulsification, bimanual MICS with the STAAR Wave System resulted in significantly better postop uncorrected visual acuity than coaxial phacoemulsification.

The study, by Dr. Fine and his colleagues, included four systems for microphacoemulsification: the Alcon Legacy with NeoSonix, the Bausch & Lomb Millennium in phaco burst mode, the Advanced Medical Optics Sovereign with WhiteStar technology and the STAAR Sonic Wave System.

“Our analysis showed that more eyes had uncorrected visual acuity of 20/40 or better within 24 hours of surgery with the STAAR system combining ultrasonic and sonic emulsification compared to sonic alone,” Dr. Fine said. This difference was statistically significant (P = .01), he said.

There was no significant difference between bimanual MICS and coaxial surgery in the percentage of clear corneas after surgery or uncorrected visual acuities with all the other systems, he said.

Dr. Fine said the main point is that while bimanual phaco does not necessarily produce better outcomes at this time, it is not worse than coaxial phaco, it is a safer procedure, and it has the potential to produce improved outcomes.

But is it MICS?

Dr. Osher was less enthusiastic about the advantages of bimanual MICS without ultrathin IOLs.

“To carry out the surgery right now, surgeons have to either add a third incision of 2.75 mm to implant the IOL in addition to their two 1.5-mm incisions for bimanual phaco, or they have to manipulate one of their stab incisions to increase it to 2.75 mm to inject the IOL through it,” Dr. Osher said.

“Either way you look at it, you are increasing your total chord length for all incisions to 5 mm or 6 mm,” he continued. “This is not microincision surgery, it’s macroincision surgery.”

Dr. Osher said that coaxial phacoemulsification with a 1-mm side-port incision and a main phaco incision of 2.75 mm (with a total chord length of 3.75 mm) is actually less invasive and more efficient than the current bimanual MICS techniques surgeons are performing in the United States.

Dr. Lindstrom agreed. “I don’t think that there is any measurable benefit to bimanual MICS except the smaller incision. If surgeons need to increase the incision size to fit a standard IOL, then it’s not worth the effort,” he said.

Currently, Dr. Lindstrom said, he performs bimanual MICS in about 10% of his cataract cases.

He said he has had little success teaching the technique to his fellows, who find it difficult to learn and more complicated than coaxial phacoemulsification.

“I currently tell my fellows to focus on making coaxial better,” he said.

Incision size vs. benefit

Dr. Lindstrom said that if the final cataract incision size can be reduced from 3 mm to 1.5 mm or 2 mm, the amount of surgically induced astigmatism may be minimized to near zero.

He explained that laboratory studies of the properties of astigmatism have shown that a certain amount of incision length reduction is needed to produce a significant improvement in astigmatism induction.

“For a significant clinical benefit in induced astigmatism, one needs to reduce incision size by 1.5 mm or greater,” he said. “A 1 mm smaller or 0.5 mm smaller incision is not going to give us better outcomes, but going from 3 mm in coaxial phacoemulsification to a 1.5-mm incision in bimanual surgery will probably be significant, although the return is getting smaller,” Dr. Lindstrom said.

He explained that the true size of the incisions in bimanual MICS, and subsequently the measurable benefit of the procedure as compared to coaxial cataract surgery, will vary among surgeons depending on the diameter of the irrigating device and phaco tip they choose. Additionally, the incision chord length will vary with the technique and instruments used.

“Microincision surgery will vary from 2.5 mm to 1.5 mm depending on the tools you choose and the method you choose to remove the nucleus,” Dr. Lindstrom said.

He added that once ultrathin lenses are approved in the United States, surgeons who prefer a one-handed phaco technique to bimanual phaco can utilize MICS with appropriate phacoemulsification systems, with a one-handed technique and coaxial handpiece.

Three-plane design

Currently, Drs. Lindstrom, Osher, Fine and Packard each perform bimanual MICS with a slightly different technique.

Dr. Osher said he uses a three-plane design for his microincision, which is tighter and more competent than a paracentesis stab incision.

“I make a groove in the near-clear cornea, not pure clear cornea and not a tunnel in the sclera. At the limbus there are vessels, which gives you more surface area to create an incision that heals better after surgery and maintains integrity better during surgery. Then I make an uphill and then a downhill incision for a three-plane incision,” Dr. Osher said. The structure of this 2.75-mm incision allows the IOL to glide through it and does not require suturing after surgery.

Dr. Osher said he places a second instrument in the second incision during hydrodissection and hydrodelineation to allow fluid to leak out of the eye.

“This is very important because fluid doesn’t easily exit the eye when you are trying to hydrodissect through a 1.5-mm incision. Pressure can get dangerously high,” he said.

Dr. Osher said there are three new elements the coaxial phaco surgeon must learn to control in switching to a bimanual MICS technique. He said chamber dynamics change because the 20-gauge irrigating instruments let in less fluid than the coaxial phaco sleeve. Therefore, the vacuum and aspiration must also be turned down, reducing the efficiency of the procedure. Second, management of the nuclear fragments is more challenging with the smaller phaco tip. And third, the surgeon must be conscious of thermal concerns with the sleeveless phaco tip and understand the importance of hyperpulse and duty cycle.

“All of these factors are crucial, and I feel that, while microphaco is inevitable, there is little benefit to be doing it right now until the small-incision lenses are approved in the United States,” Dr. Osher said. “Still I can perform MICS safely with the Alcon Infiniti system and Duckworth and Kent instrumentation.”

Smooth, continuous irrigation

Dr. Fine said he uses a triple incision technique, two for the bimanual hand-pieces and one for IOL implantation, that he called “quite simple and easy to learn.”

First, two 1-mm clear corneal stab incisions are created with a Mastel Fine Paratrap diamond knife, 60° to 90° apart, on either side of the temporal peripheral cornea. These accommodate the irrigating instrument and the phaco tip.

He creates a 5-mm capsulorrhexis with forceps, then performs cortical cleaving hydrodissection and hydrodelineation.

“We then use a MicroSurgical Technology chopper to chop and evacuate pie-shaped segments,” Dr. Fine said. The chopper is then turned sideways, so it is not pointed downward, and the roof and distal rim of the epinucleus are aspirated and emulsified.

“We rotate the epinucleus with the phaco needle in continuous irrigation and then trim and remove the roof and rim,” he continued. “This is done in three quadrants distally, and then we rotate the fourth quadrant of the rim distally and use that as a handle to flip the epinucleus. We use the incoming stream from the irrigating chopper to flip the epinucleus, rather than pushing against it, and in about 70% of cases the entire cortex comes out.”

The capsule is cleaned and polished with bimanual irrigation and aspiration before the IOL is implanted through a 2.75-mm incision, newly created between the two 1-mm stab incisions.

“We never enlarge the microincisions for IOL implantation because there is a lot of manipulation through those two incisions that stretch them a little. We make that incision between the two incisions. When we have a lens that will fit through those incisions without enlarging them, we will use those. But we think this technique is just plain better than coaxial phaco,” Dr. Fine said.

Enhanced fluidics

Dr. Packard said he has been performing bimanual MICS for almost 5 years now. He places his two incisions 70° to 80° apart.

He said several factors contribute to a successful bimanual MICS technique. The first is that, to prevent leakage, incision size must match the instrument used.

“This alone will enhance the fluidics of any phaco machine,” he said.

A second significant aspect of successful microincision phaco is achieving safe and effective fluidics. He said he prefers to use a phacoemulsifier with a peristaltic pump and appropriate surge control, such as the Alcon Infiniti or the AMO Sovereign.

“The irrigating chopper I use is made by Duckworth and Kent, and although slightly larger than some at 18 gauge, it delivers 82 cc per minute, which helps considerably with chamber stability,” Dr. Packard said. “Power delivery with minimal energy use is essential for microincision surgery.”

With the AMO Sovereign system, Dr. Packard said he uses a continuous micropulse mode with a 30% duty cycle to obtain occlusion.

“The machine changes automatically to four long pulses per second of micropulsing with a 20% duty cycle. This assists in tissue removal,” he explained.

Chamber maintainer

Dr. Lindstrom said he enhances fluidics in his bimanual cases with use of an anterior chamber maintainer through an additional incision.

“The chamber maintainer allows me to use my manipulator of choice in my left hand without the extra bulk of having infusion come through it,” he said.

Dr. Lindstrom said he is currently working with ophthalmic companies to create chamber maintainers for MICS, similar to those used in vitrectomy, to allow for increased flow.

“I just plug in the maintainer, which lets you just step on the pedal and have your hands free to remove the nucleus with your usual nucleus manipulator,” Dr. Lindstrom said.

He uses this three-port microincision technique for bimanual surgery with a tilt-and-tumble technique.

“I do supracapsular phaco. I hydrodissect until the nucleus tilts up into the iris plane. I don’t need a chopper or cracker for this technique,” he said.

First steps

Surgeons interviewed for this article offered some suggestions for those interested in adopting a bimanual technique. Several suggestions taking a course in MICS at upcoming ophthalmic meetings or visiting surgeons who have already adopted MICS and teach the technique in their practices.

Dr. Lindstrom suggested that surgeons can ease into the idea of bimanual cataract surgery by using bimanual irrigation and aspiration after their coaxial phaco procedure.

Above all else, surgeons should not compromise the safety of cataract surgery to satisfy a personal desire or interest, Dr. Osher said.

“At the end of the day, the surgeon who is still doing performing coaxial phaco is not making any compromise to the quality of care for his current patients,” he said.

Dr. Osher noted that the first issue of the 2004 Video Journal of Cataract and Refractive Surgery demonstrates numerous MICS techniques by leading surgeons, including those interviewed in this article.

For Your Information:

• Richard L. Lindstrom, MD, can be reached at Minnesota Eye Consultants, 710 E. 24th St., Suite 106, Minneapolis, MN 55404; 612-813-3600; fax: 612-813-3660; e-mail: rllindstrom@mneye.com. Dr. Lindstrom has a financial interest in Bausch & Lomb, Advanced Medical Optics, STAAR, BD, TLCVision, Midwest Surgical Services and Minnesota Eye Consultants.
• Robert H. Osher, MD, can be reached at the Cincinnati Eye Institute, 10494 Montgomery Road, Cincinnati, OH 45242; 513-984-5133; fax: 513-936-4881; e-mail: rhosher@cincinnatieye.com. Dr. Osher is a paid consultant for Alcon.
• I. Howard Fine, MD, can be reached at Drs. Fine, Hoffman and Packer, 1550 Oak St., Suite 5, Eugene, OR 97401; 541-687-2110; fax: 541-484-3883; e-mail: hfine@finemd.com. Dr. Fine is a paid consultant for Advanced Medical Optics, Bausch & Lomb, Pfizer Ophthalmics and iScience. He receives travel and research support from Alcon, Eyeonics and STAAR Surgical.
• Richard Packard, MD, FRCS, FRCOphth, can be reached at Arnott Eye Associates, 22a Harley St., London W1, England; e-mail: eyequack@vossnet.co.uk. Dr. Packard is a consultant for Alcon on the Infiniti system.

• STAAR Surgical, manufacturer of the Sonic Wave System, can be reached at 1911 Walker Ave., Monrovia, CA 91016; 626-303-7902; fax: 626-358-9187.
• Alcon, manufacturer of the Legacy and Infiniti, can be reached at can be reached at 6201 South Freeway, Fort Worth, TX 76134; 817-293-0450; fax: 817-568-6142.
• Advanced Medical Optics, maker of WhiteStar Technology for the Sovereign System, can be reached at 1700 E. St. Andrews Place, Santa Ana, CA 92799; 800-449-3060; fax: 866-872-5635; Web site: www.amo-inc.com.
• Bausch & Lomb, maker of the Millennium, can be reached at 1400 N. Goodman St., Rochester, NY 14609; 585-338-5212; fax: 585-338-0898; Web site: www.bausch.com.

• OSN Staff Writer Nicole Nader covers pediatrics and strabismus and neuro-ophthalmology in addition to cataract and refractive surgery.