REFRACTIVE SURGERY

Compensation vs. Accommodation

Surgical strategies to treat presbyopia are gaining momentum and spawning debate. Here’s information that will help you advise your patients.

Amy Black,
Managing Editor

Surgical correction for presbyopia is still considered experimental and controversial, especially since there’s no tried-and-true method to achieve binocularity. Some surgeons, however, are pushing the envelope and are investigating procedures that may some day be available to your patients.

There are two schools of thought when it comes to surgical treatments for presbyopia. The first, the compensation school, advocates using lasers to induce monovision or multifocal optics to manipulate the lens or cornea. The second, the accommodation school, is testing new intraocular lens implants and is even trying to reverse presbyopia.

To which school do you belong? More importantly, how will you answer patients’ questions about these options? Here’s information that will help you decide.

Monovision Surgery
Laser-induced monovision is arguably today’s most widely accepted surgical treatment for correcting presbyopia. On the plus side, it’s a relatively well-known entity, and you have a pretty good idea what the outcome will be, provided there are no complications. But this is a huge responsibility for optometrists because success often depends on patients’ pre-op expectations.

Patient selection is especially important. J. James Thimons, O.D., recommends finding out what your patient does at work and at play. “One group you can rule out right away for monovision: long-distance drivers,” he says. And, monovision can affect depth perception.

Also consider that monovision is entirely different in theory than in real life. Subjective response is 90% of the battle. “When patients notice that they have to flip their mind from one eye to another, they’re not good candidates,” Dr. Thimons says. This is one reason many optometrists advocate for monovision with contact lenses before the patient undergoes laser surgery. With monovision contact lenses, the patient’s expectations more closely match the actual results.

Besides, you can’t really put into words what monovision feels like.

Modified monovision is another potential surgical option. It can alleviate some of the adjustment problems a patient might have with traditional monovision because it results in less anisometropia. Modified monovision procedures usually leave the patient with 0.50D to 0.75D of residual myopia vs. the standard 1.00D or more.

This smaller residual error may allow some patients to adapt more easily to the difference between their two eyes. Also, these patients may not lose as much depth perception as with conventional monovision. In fact, Dr. Thimons says most patients experience a seamless transition.

The Baikoff phakic refractive multifocal lens has semi-rigid PMMA haptics.

Multifocal IOLs
There used to be a clear divide between cataract and refractive surgery. Your patient complained he couldn’t see, you discovered cataracts, referred him for surgery, and soon afterward he was back for a new pair of glasses. Not anymore. The Array multifocal intraocular lens from Allergan changed that somewhat by reducing some post-cataract surgery patients’ dependence on glasses. But, controversy continues to surround the use of this lens.

For cataract or even clear lens patients, careful patient selection is one of the most important considerations. Many patients get significantly improved vision but can’t live with the glare and haloes often associated with the lens. So, it’s important that you get to the bottom of what your patient values most and what compromises he’s willing to make to get it.


The AT-45 IOL flexes at the junctions between the optic and the haptics, allowing it to move forward during accommodative effort.

Another possible but even more controversial way to use the Array: Some aggressive surgeons consider clear lens exchange a legitimate option for presbyopes without cataracts. The procedure is called PRELEX, or presbyopic lens exchange, and some surgeons believe it could become commonplace in the next few years.

Paul M. Karpecki, O.D., of Kansas City, has worked with Array patients since the lens was first introduced. “There are limits to LASIK because of corneal thickness, so sometimes a lens procedure might be best,” he says. The downside to PRELEX: “Keep in mind that you remove remaining accommodation, and there’s an increased but low risk of retinal detachments, especially in myopic patients.”

Although the Array is the only FDA-approved aphakic lens with multifocal optics, others are in the works. The MF4 is an acrylic multifocal foldable IOL that IOLTech makes. The lens has four annular zones (two for distance and two for near) with a maximum +4.00D add. The MF4 for aphakia correction is in early clinical trials. IOLTech has also developed a phakic refractive multifocal lens with three zones, which CIBA Vision will distribute. Called the Baikoff phakic IOL, for co-developer Georges Baikoff, M.D., of France, it has a tripod shape and soft footplates composed of hydrophilic acrylic.

CIBA Vision expects the lens to be available in Latin America in 2001 and in Europe possibly as soon as next month. CIBA may use the data collected from the ongoing trials abroad to apply for additional approvals, ultimately leading to FDA clinical trials.

To date Dr. Baikoff has implanted the bifocal lens in six eyes to correct +2.50D to +3.00D of presby- opia. One patient received bilateral IOLs; two lenses were explanted due to incorrect sizing. Patients were 50 to 55 years of age; plano prior to surgery; and required +2.50D to +3.00D add to achieve good reading vision. With the exception of one patient, Dr. Baikoff implanted the lens unilaterally.

The results at 4-6 months out show three eyes at 20/20 uncorrected and J1 with no add; one eye at 20/25 and J1 with no add. In this limited series, no complications were seen, but loss of contrast sensitivity and ghosting are possible side effects.

Another new multifocal concept still in development: intracorneal inlays. The surgeon places these clear 2mm hydrogel inlays in a deep lamellar corneal pocket, and they may create a multifocal cornea. Exact design and placement are still being worked out, but the goal is to offer presbyopic patients good near vision without compromising their distance vision.

Accommodating IOLs
Some aggressive surgeons are more willing to bet on an IOL that accommodates rather than one that compensates. Aliso Viejo, Calif., surgeon J. Stuart Cumming, M.D., invented one such IOL, the AT-45. C&C Vision is helping to develop this foldable, silicone lens.

About 8 years ago, Dr. Cumming noticed that many of his pseudophakic patients could see at both distance and near without glasses. And, patients with plate silicone lenses tended to perform better at reading tasks. After doing some A-scan studies, he found that these IOLs tended to move forward with accommodation. This led Dr. Cumming to design a lens that could take advantage of this movement.

The AT-45 has a hinge-like modification at the junction of the plate haptic that allows the optic to flex forward with accommodation. This allows the eye to bring closer objects into sharp focus. The lens is presently in FDA clinical trials.

Four steps of the Schachar procedure (clockwise from bottom right): 1) the surgeon makes an incision, 2) widens the pocket, 3) then inserts the segments into the pocket, 4) the segment in place.

Surgical Reversal
The quest to restore accommodation in presbyopes is also gaining momentum, thanks in large part to Ronald Schachar, M.D., of Dallas, who proposed a new theory on the loss of accommodation.

Dr. Schachar theorizes that in accommodation the anterior radial ciliary muscle fibers arch toward the sclera, increasing tension on the equatorial zonules. This produces central steepening and peripheral flattening in the lens. However, the lens is composed of ectodermal biological material, which means that it grows continuously throughout life. This causes zonular tension to slacken, preventing the ciliary muscle from functioning properly. Accommodation suffers.

To gain zonular tension and allow the muscles to work, Dr. Schachar developed Scleral Expansion Bands (SEB), manufactured by Presby Corporation. This procedure is currently in phase I FDA clinical study and if approved may restore on average 3.25D of accommodative amplitude, with a range of 1.50D to 6.00D. Possible complications include transient subconjunctival hemorrhage and loss of effect if the segments are placed incorrectly.

John LiVecchi, M.D., of Scranton, Pa., has developed a slightly different procedure based on Dr. Schachar’s theory. In the 10 patients Dr. LiVecchi reported on at this year’s American Society of Cataract and Refractive Surgery (ASCRS) meeting, he achieved an average restoration of accommodation of 2.68D. Post-op side effects included foreign-body sensation, conjunctival injection and edema, mild brow headache, corneal abrasion and conjunctival erosion.

Another method that is presently under investigation for restoring accommodation is laser presbyopia reversal (LAPR). Using the IR 3000 solid state, fiber-coupled, infrared “cold” laser, SurgiLight is studying a technique that may be used to relax and expand the sclera that overlies the ciliary body. The IR 3000 system is in clinical tests in Venezuela, and the company has also scheduled installation of the IR-laser in Europe.

Clinical results that were presented at the Summer Refractive Surgery Symposium meeting this year show that 86% of the 35 treated patients can read J3 or better after the surgery. Almost no regression was found up to 13 months post op.

There are a lot of contestants in the race to surgically treat presbyopia. And, like other important issues of our day, it’s still too close to call which one will reign. But, judging by the high acceptance ratings of other refractive procedures, patients will want to learn more—and they’ll look to you for advice. u

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