SIZING UP Surgical Options for Presbyopia

Prepare to hand your presbyopic patients a menu of safe and effective procedures.

BY ROBERT MURPHY

Long the scourge of the normal aging eye, presbyopia is up against a new alliance of therapeutic interventions, some corneal-based, some lens-based, which promise risk-benefits profiles far outperforming those of traditional spectacle or contact lens remedies.

Three approaches—corneal inlays, presbyopic lens exchange and presbyopic laser treatment—have captured the attention, time, capital and expertise of investors, scientists in the academy and developmental start-ups, investigative surgeons, regulators and, of course, patients. A fourth category, scleral implants, hovers at an early stage of development. While corneal inlays await FDA approval, and each method carries some visual compromise and risk, you can prepare to hand your presbyopic patients a menu of safe and effective procedures.

Corneal Inlays

Perhaps the brightest star in this surgical pantheon is one still seeking the FDA’s imprimatur. Presbyopic-correcting corneal inlays have been approved just about everywhere else outside of the Arctic, and at least one company leads the race to clear the FDA’s hurdles within the next year or two. Each of three types of corneal inlays works according to a different principle.

A rendering of the Kamra corneal inlay as it looks in the eye.

► Kamra (AcuFocus, Irvine, Calif.). Expected to appear first on the US market, the Kamra corneal inlay reportedly has completed trials in the United States. Now, it’s a matter of collating and analyzing heaps of data, no small task and a time-consuming one.

“The AcuFocus concept uses the optical principles of the cornea to increase the depth of focus,” says Daniel Durrie, MD, of Overland Park, Kan. Many refer to the design as producing a pinhole effect, although Dr. Durrie sees this as something of a misnomer, preferring the term “small-aperture optics.” “Pinholes block too much light,” Dr. Durrie says. “It’s more like the F-stop of a camera. When you narrow the stop of a camera, you increase the depth of focus.”

The Kamra inlay has its pros and cons. “It works because the pupil changes size when you’re reading and when you’re looking at distance,” says Michael Gordon, MD, of San Diego. “The positive of that, according to the studies, is that it really doesn’t impact your distance vision although you’re looking through a pinhole. The negative is, cosmetically it may not be acceptable for blue-eyed individuals; you can see it. The other thing is, reading and poor light situations may not be the best because the pupil doesn’t constrict.” Night vision therefore may be compromised.

A slit-lamp image of the Flexivue corneal inlay.

Smaller than a needle thread hole, the Raindrop inlay as it appears in the eye.

■ The Presbia Flexivue Microlens (Presbia, Los Angeles). corneal inlay works by means of “smart” monovision by producing a bifocal optical system. “It actually bends light,” Dr. Gordon says. The Presbia Flexivue Microlens is implanted in the non-dominant eye of patients. “As your pupil gets smaller, patients can read because it produces a monovision effect. When the pupil dilates for distance, you’re looking around the lens, and distance vision is minimally affected.”

The central, inner zone of the Presbia Flexivue Microlens contains no refraction, and is used for distance vision (i.e., during far vision light passes through this zone of no refraction and is sharply focused on the retina). The peripheral, outer zone contains the near refractive power for near vision correction (i.e., during near vision light passes through this zone with refraction and is sharply focused on the retina). As with traditional monovision, patients require time for neural adaptation.

The Presbia Flexivue Microlens shares a virtue with other presbyopic corneal inlays in that the procedure is reversible. That can make a big difference if a patient’s visual needs evolve with age. “The beauty of this procedure is, you can select the power of the implant that you want — that’s from 1.50 D to 3.50D — and change it as the patient gets older,” Dr. Gordon says. “You can take the lens out and put in a stronger implant.” Likewise, patients dissatisfied with their vision can simply have the lens removed without negatively affecting the patient’s cornea.

■ Raindrop Near Vision Inlay (ReVision Optics, Lake Forest, Calif.). The refractive index of this 2 mm-diameter inlay, formerly known as the Vue+ and PresbyLens, matches that of the cornea.¹ Placed under a femtosecond laser flap and centered on the light-constricted pupil, the Raindrop actually alters the cornea’s anterior curvature. The inlay creates a prolate effect that improves near and intermediate vision while permitting distance vision through the peripheral cornea.

The Allure of Corneal Inlays

Corneal inlays as a category offer key advantages. “It’s attractive to the patient that the inlay adds to the cornea and doesn’t subtract from it,” Dr. Durrie says. “It can be used in a large range of patients who had lens implantation in the past, and all of those seemed to have success on the international market.” The procedure so far has proven quite safe. Technically, it’s relatively easy to perform.

But such a device can have its downside. “The disadvantage is that it needs to be put in the right place and done with the right equipment,” Dr. Durrie says. As with all presbyopic surgeries, patient selection is critical. “It does require some adaptation for the patients, but it’s shorter than [traditional] monovision. People adapt to the optical system within weeks rather than months,” he says.

Presbyopic Lens Exchange

Adding to the array of surgical options are new designs of implants and techniques for presbyopic, or refractive, lens exchange. Here, too, multiple improvements are available.

“The lenses themselves are approved, but a lot of the steps associated with the surgery are now also approved,” says Indianapolis surgeon Kevin L. Waltz, MD, OD. “Back in the ‘90s, a lot of people would have a contact A-scan and a manual keratometry preoperatively to predict the lens position. Now we have laser interferometry for axial length measurement, and we have corneal topography for corneal curvature. So our ability to predict and calculate the IOL is better.”

Alcon Laboratories’ multifocal Acrysof ReStor IOL.

Until recently surgeons had but two options for presbyopic lens exchange: monovision and the pioneering AMO Array lens.² Now Bausch + Lomb’s accommodative IOL Crystalens, Alcon Laboratories’ multifocal Acrysof ReStor and AMO’s Tecnis and ReZoom lenses are available.²

“The most powerful technology, I think, is presbyopic lens exchange with a multifocal IOL,” Dr. Waltz says. “Because you can fix things that you can’t even think about fixing with the laser. If you’re +8.00 D, and you want to see distance and near, I can give you a lens, no problem. In the past, we had no power to fix that. Now we can.”

Here, too, patient selection is critical. “These are patients who are candidates to have their lens removed,” Dr. Durrie says. “If the patient is 55-years-old, and is 2.00 D hyperopic, and has a little nuclear sclerosis, I think most people feel that’s a patient where the presbyopia should be addressed in the lens, if they’re going to have surgery—especially if it looks like they’re going to need cataract surgery in the next five to 10 years.”

A key caveat with presbyopic lens exchange: Be careful with myopes, especially those with significant refractive error. They are notoriously at risk for retinal detachment with this procedure.

“Myopes have a detachment risk if you do lens-based surgery,” Dr. Waltz says. “Emmetropes and hyperopes in general do not. If you’re a myope, you have a risk of retinal detachment whether you have surgery or not. We’re not yet sure whether lens-based surgery increases the risk further, but they have a baseline risk. They have a longer axial length, but we’re not sure that’s the cause of it.”

The Tecnis and ReZoom IOLs from AMO.

Presbyopic LASIK

Corneal laser procedures for presbyopia essentially produce a monovision effect, or a form of blended monovision. Surgeons have been performing different forms of laser monovision for years, mostly with great success. New approaches are in use in Europe and elsewhere, while in the United States surgeons perform it off-label because no companies have filed for monovision approval, Dr. Durrie says.

The accommodative Crystalens IOL from Bausch + Lomb.

“There are multiple technologies that are available in Europe in terms of laser vision correction options to enhance depth of focus,” says Ronald Krueger, MD, of the Cleveland Clinic. “There are different ways of having a profile of laser vision correction that lead to a little extra negative spherical aberration on the surface of the cornea that enhances the depth of focus and still maintains some level of distance correction, too.”

Dr. Krueger claims great success with monovision LASIK. “I have about 92.5% of my [presbyopic-surgical] patients going in that direction, who are over age 40—and liking it,” he says.

Dr. Krueger puts to use so-called adaptive optics with special mirrors that alter the patient’s view and can be used as an effective preoperative indicator of what the patient can tolerate visually. “You can see how much they tend to tolerate in order to understand some of the [lens parameters] that are best,” Dr. Krueger says. “And I’m hoping that adaptive optics can give us better information about how to design either inlays or multifocal corrections to really help these people get the most benefit with the least compromise.”

Scleral Implants

Still in developmental infancy are presbyopic-correcting scleral implants, most notably the PresView device from the Refocus Group in Dallas. “That is a scleral implant that is placed in all four quadrants in a scleral tunnel,” Dr. Gordon says. “This is done binocularly. The theory is that it will improve your ability to accommodate.”

The jury is still out on this one, at least theoretically. “Now, whether it truly works like that, nobody really knows,” Dr. Gordon says. “But it does seem to have a very positive impact on one’s ability to read.” Expect some years to pass before scleral implants get FDA approval.

Near, Far: Aiming for Par

Reading glasses, progressive lenses, monovision contact lenses, and multifocal contact lenses are hardly ready for history’s trash heap. Lots of people like them. But look for a growing population of patients seeking a one-time yet permanent solution to a visual affliction that snuck up like gray hair.

These are the potential candidates for presbyopic corneal inlays, presbyopic lens exchange, modified monovision LASIK, and perhaps someday scleral implants—a sizeable and expanding market of individual yet pressing visual needs. Hence, the efforts to develop remedies with varying mechanisms of action to best suit the case at hand.

Dr. Gordon ranks among the enthusiasts. “I think all of us in ophthalmology realize that presbyopia is not the final frontier, but close to it, for refractive surgery,” he says. “A lot of energy, and research money, and research time are being put into finding a solution. And I think we’re getting closer and closer with better options.” Multitudes worldwide with aging eyes likely will embrace this as promising news. OM

References

1. Doran M. Corneal inlays for presbyopia move closer to approval. EyeNet Magazine. 2010;14:25-26. Available at: http://www.aao.org/publications/ eyenet/-201003/refractive.cfm. Accessed November 28, 2012.

2. Schena LB. The refractive lens exchange debate. EyeNet Magazine. 2005;9. Available at: http://www.aao.org/publications/eyenet/200506/feature.cfm. Accessed November 28, 2012.