Incisional techniques make comeback for refractive correction

Two surgeons explain why mini-RK and LRIs have a place today in the correction of myopia and astigmatism.

Incisional refractive surgery has made way for burgeoning laser techniques in recent years, but it remains a viable alternative for treating myopia and astigmatism in some patients, according to two surgeons.

Incisional techniques are generally safe, economical and easy to learn, but there are some downsides, they said.

In addition, toric IOLs provide another alternative to incisional techniques.

“I think there is going to be a horse race here between toric IOLs and limbal relaxing incisions. Some surgeons will just never use limbal relaxing incisions if they have toric IOLs,” OSN ASC Section Editor R. Bruce Wallace III, MD, said.

R. Bruce Wallace III

Dr. Wallace attributed the decline of incisional techniques to many younger surgeons’ lack of experience in using them.

“Many surgeons didn’t have a practice during the RK days,” Dr. Wallace said. “They weren’t even in residency during the RK days, so they don’t really understand exactly how to do the procedure and they don’t have the equipment available.”

Richard L. Lindstrom, MD, OSN Chief Medical Editor, said incisional refractive surgery is a “lost art” that is making a comeback.

“The reason it is gaining popularity is that it’s very quick and easy to do just in the office, very inexpensive to do, and you can do enhancements for post-cataract surgery patients who have residual refractive error,” Dr. Lindstrom said.

However, incisional techniques offer less predictability than laser-based techniques, except when it comes to correcting small refractive errors, he said.

Mini-RK

Dr. Lindstrom recalled helping to develop minimally invasive radial keratotomy (mini-RK).

Richard L. Lindstrom

“Typically, incisions are only about 2 mm in length, and often you only need two of them to correct small amounts of myopia in the older patient,” he said.

Two-incision mini-RK is ideal for patients with mild myopia and astigmatism, Dr. Lindstrom said. Four-incision mini-RK with a large optical zone, up to 5 mm, is best for post-IOL insertion enhancement for mild myopia without astigmatism.

“It turns out that this type of procedure doesn’t destabilize the cornea,” he said. “It’s quick and easy to do.”

Two-incision mini-RK and four-incision mini-RK result in a low amount of trauma to the cornea, offer reproducible results and cause less dry eye than surface ablation or LASIK, Dr. Wallace said.

“I think there is still a place [for mini-RK], despite the fact that LASIK is definitely, technologically speaking, more advanced and probably is more reliable and more accurate. But in low levels of myopic treatment, there is a place for RK,” he said.

However, many surgeons are not familiar or comfortable with mini-RK, Dr. Wallace said.

“They never did it to begin with or they haven’t done it in years because they’ve transferred over to a laser,” he said.

Dr. Lindstrom also helped develop the arcuate-T incision for astigmatic keratotomy. The surgeon places arcuate, transverse relaxing incisions at the 8-mm optical zone. A 2-mm incision at the 8-mm optical zone can correct 1 D of astigmatism, Dr. Lindstrom said. A 3-mm or 45° arc incision can correct up to 2 D of astigmatism, and a 3-mm or 60° arc incision can correct 3 D of astigmatism.

“You can use any combination that you want, so basically you have a system that can correct from 1 D to 6 D of astigmatism, which is a very powerful tool,” he said.

Limbal relaxing incisions

Limbal relaxing incisions (LRIs) are used during and after cataract surgery to correct astigmatism that is often surgically induced, Dr. Wallace said.

He said wet labs that demonstrate LRIs at the American Academy of Ophthalmology and American Society of Cataract and Refractive Surgery meetings are popular with surgeons. “They know that they can’t just read a book on this. They have to get trained,” he said.

However, LRIs suffer from a lack of industry support and low public awareness, Dr. Wallace said.

“There’s not as much hype,” he said. “There’s not as much interest in the public eye compared to LASIK. You don’t see a lot of people coming in and saying, ‘Can you do an LRI on my eye?’ That’s not happening.”

Managing perceptions

Public perception of astigmatism may also hamper the potential growth of LRIs, Dr. Wallace said.

“The term astigmatism sounds bad. It sounds like rheumatism, something that’s a disease. They just don’t understand it, so you have to explain what astigmatism really is, and that slows everything down,” he said.

“Patient counseling becomes a little more complicated when we start talking about correcting astigmatism,” he said.

Dr. Wallace questioned why LRIs have not been popular all along, considering the low cost and clinical advantages, such as incisions being on the periphery of the cornea, a low complication rate and rapid healing.

He noted that some surgeons have overcome their trepidation about doing LRIs.

“I think more and more refractive cataract surgeons are waking up to the fact that IOL calculations are one thing, but they also have to do something about astigmatism, so we’re seeing limbal relaxing incisions becoming more popular as they get through this concept that it’s really not RK,” he said.

For LRIs to be effective, Dr. Wallace recommended placing the incision 1 mm to 1.5 mm anterior to the limbus. “These are really peripheral corneal incisions, not limbal incisions,” he said.

Dr. Wallace also predicted that toric IOLs, including the STAAR Toric IOL and the AcrySof Toric IOL (Alcon), could rival LRIs as the treatment of choice for astigmatism.

Dr. Lindstrom said he thinks that LRIs are not as effective as corneal relaxing incisions.

“To me, limbal relaxing incisions just never made sense,” he said. “They’re harder to do. I think they’re more invasive.”

LRIs use a large optical zone, up to 11 mm, which can be a disadvantage because the incisions have to be long and deep in the periphery to be effective, Dr. Lindstrom said.

“From my perspective, the disadvantage of a true LRI vs. putting the incision in the clear cornea at an 8-mm optical zone is that the LRI incision has to be much longer and they have to be deeper incisions to get good effect because the cornea is thicker at the limbus. In addition, there is some bleeding in many cases,” Dr. Lindstrom said.

He added LRIs offer less effective correction than astigmatic keratotomy.

“The amount of correction you can get is much less than you can get at an 8-mm optical zone, so you can only really correct up to about 2 D of astigmatism, whereas with an 8-mm optical zone [astigmatic keratotomy] or corneal relaxing incision, you can correct up to 6 D of astigmatism,” he said.

Overall, incisional surgery still has a role to play in the correction of astigmatism, both surgeons said.

“Certainly there is a place for incisional surgery for astigmatism. Most LASIK surgeons still offer that as an option, even to post-LASIK patients that have leftover astigmatism, because it is less of an event compared to raising a flap and adding additional excimer laser treatment,” Dr. Wallace said.

For more information:

• Richard L. Lindstrom, MD, is the Chief Medical Editor of Ocular Surgery News. He is in private practice at Minnesota Eye Consultants, 9801 DuPont Ave. S, Suite 200, Bloomington, MN 55431; 952-888-5800; fax: 952-884-2656; e-mail: rllindstrom@mneye.com. Dr. Lindstrom is a consultant for Alcon.
• R. Bruce Wallace III, MD, can be reached at Wallace Eye Surgery, 4110 Parliament Drive, Alexandria, LA 71303; 318-448-4488; fax: 318-448-9731; e-mail: rbw123@aol.com. Dr. Wallace is a consultant for Advanced Medical Optics and Allergan.

• Matt Hasson is an OSN Staff Writer who covers all aspects of ophthalmology. He focuses on regulatory, legislative and practice management topics.