30 June 2013
All that's needed is U.S. regulatory approval, most surgeons say
Corneal inlays are designed to treat presbyopia by being inserted in the non-dominant eye and correcting for near vision; distance vision remains (mostly) unaffected. Three devices are currently under investigation in the U.S., with the AcuFocus (Irvine, Calif.) KAMRA inlay already filed for regulatory approval. The remaining two devices—the ReVision Optics (Laguna Hills, Calif.) Raindrop and the Presbia Flexivue Microlens (Presbia, Amsterdam)—are in trials. "It probably doesn't matter which inlay is first to market," said John A. Hovanesian, MD, faculty member, Jules Stein Eye Institute, Los Angeles. "When we talk to patients who are presbyopic, many who have heard of monovision are just not interested. They love the idea that they can get an implant that gives them near vision without the compromises of distance vision." The inlay market overall "is very promising," said George O. Waring IV, MD, assistant professor of ophthalmology, director of refractive surgery, Storm Eye Institute, and medical director, Magill Vision Center, Medical University of South Carolina, Charleston. "In a global depressed economy, outside the U.S. it's the inlays that have increased volume for practices." Further, since "100% of people get presbyopia, there is a huge market opportunity as patients are not aging gracefully anymore," Dr. Waring said. "Some of my most motivated patients are new presbyopes who never had to wear glasses before."
Inlays "will be a game changer for those who get involved with it and are not afraid to make a flap or a pocket (or probably both)," said Jeffrey Whitman, MD, president and chief surgeon, Key-Whitman Eye Center, Dallas. "We're going to have a whole new range of products for the presbyope; if the patient really dislikes the inlay, we can remove it and the patient returns to preop vision."
The "ideal" inlay candidate is someone in the 50- to 60-year-old range, said Cees Verdoorn, MD, medical director, Lasik Centrum Oogkliniek, Boxtel, the Netherlands. He explains to patients that the inlay is a "spacer" that's placed into the cornea to make it steeper in the center. "This has to be a very precise placement, or the patient may end up with blurred vision," he said.
Dr. Hovanesian said both the Raindrop and the KAMRA seem to improve distance vision to about 20/25, with near vision close to J1 or J2. Drawbacks to the technology include the potential for decentration and the possibility that the patient may have a foreign body sensation, Dr. Whitman said.
Prior LASIK patients
People who had previously undergone LASIK are as viable candidates as those who have never had surgery, Dr. Hovanesian said. "Just go beneath the flap that already exists to place the inlay," he said. "For the KAMRA, the technique involves making a pocket, and the other inlays will probably follow suit. Assuming the cornea is thick enough to have some space, the small pocket is unlikely to cause significant damage to the first flap, particularly if it's been years since the first flap was made."
The devices also have the potential to extend the LASIK market for people who are in their late 40s or early 50s, he said. In the Netherlands, Dr. Verdoorn creates a 150-micron, 8 mm flap with a 150 kHz femtosecond laser, and suggests surgeons ensure the flap is well centered before proceeding, especially in hyperopes. "These need to be in the best position possible to get the best possible vision," Dr. Whitman said. "If the inlay is not positioned properly, it might affect distance vision." He has yet to have that happen in any of his patients, but did note the possibility.
These devices have short learning curves, Dr. Waring said. "Any corneal refractive surgeon can pick it up very quickly," he said. "Using an advanced femtosecond laser is important for the pocket or flap. Centration is important, too—inlays are forgiving enough that patients will do well as long as the inlays are generally placed correctly. And, of course, patient selection is critical. We recommend healthy eyes—you really want to optimize the ocular surface."
The KAMRA can be "easier to see during the day if the light hits it right," Dr. Whitman said. "Other inlays are transparent. That may be an issue for some people."
The KAMRA works by small aperture optics (basically a pinhole in the center of the pupil), Dr. Hovanesian said. "It does reduce light entering the eye, but it doesn't seem to be clinically problematic for patients or cause difficulty with nighttime glare or contrast."
Dr. Whitman said the Raindrop allows surgeons to go about 150 microns deep, whereas the others need the inlay placed about 200 microns deep, "which we normally wouldn't be comfortable doing with LASIK."
He describes the implantation technique as simply lifting the flap, looking under the microscope, and placing the inlay "as best you can" over the center of the pupil. "The Raindrop is a very forgiving inlay," he said. "If it moves 0.5 mm this way or that way it doesn't seem to affect vision." The surgery itself it short—about 5 minutes—and Dr. Whitman said within the first 10-15 minutes after surgery patients are already sitting and reading. Currently, Dr. Whitman uses a 110 micron flap for his LASIK patients, but has changed the depth in all non-dominant eyes to 150 microns "just in case down the road this is something the patient wants done."
Patients he's discussed the procedure with tend to view the inlays as more of a lifestyle choice. "It's like Botox in terms of making them feel younger," Dr. Whitman said. Patients like the idea of the Raindrop "because it's made out of the same material as soft contact lenses, which is known as a safe material," Dr. Hovanesian said. "There are few materials that we have greater experience with than hydrogel, so people have an inherent comfort level." He added the Raindrop "probably alters the corneal curvature so there needs to be some allowance for that in the biometry, but it's along the lines of someone who has undergone hyperopic LASIK."
In the U.S., studies are evaluating the device in near emmetropes, but outside the U.S., inlays are undergoing trials with simultaneous LASIK, Dr. Whitman said.
"Once the Raindrop is approved I think you'll see a lot of surgeons combining it with LASIK," he said. "It's got the potential to change how we look at premium lens implants in the future." For instance, the age of the ideal inlay patient is pre-cataract, so "there may be no reason to do a premium lens implant on them later on," he said. With "literally billions of presbyopes, including a good number who had prior laser surgery," corneal inlays represent a "really good option," Dr. Hovanesian said. "Inlays allow us to provide a visual experience that is as rewarding to a 45-year-old as LASIK is for a 25-year- old."
Inlays represent "a truly lifelong benefit. There are not too many procedures we can give our mid-40s patients that will benefit them forever," he said. But once the inlays are approved, "a whole new world is in front of us."
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