Synthetic keratophakia shows potential for hyperopic correction

SAN FRANCISCO — Synthetic keratophakia could be an alternative to LASIK for correction of hyperopia, according to a presentation here.

In synthetic keratophakia, a small lens is implanted under a corneal flap. The procedure could potentially correct a large range of hyperopia, said Stephen G. Slade, MD, speaking here at VisionQuest 2002.

“Keratophakia ... is a very powerful technique because you do not have to correct the entire cornea. It is a removable, potentially reversible refractive effect,” Dr. Slade said. “It’s an additive technology rather than a subtractive technology.”

Dr. Slade said hyperopic LASIK requires removal of up to 2.5 times as much corneal tissue as myopic LASIK to get the same number of diopters of correction. But in synthetic keratophakia no tissue is removed, and thus the procedure "is not limited by the patient’s original corneal thickness or anything specific to the patient,” Dr. Slade commented.

The procedure employs the PermaVison intracorneal implant from Anamed Inc., which recently completed a phase 1 Food and Drug Administration feasibility trial involving 10 patients. Dr. Slade said results of the study were comparable to those seen in hyperopic LASIK.

Dr. Slade noted that, because of the curvature of the implant, “if you invert it, you get a decrease in the best corrected vision.”

He also noted that two patients in the feasibility trial experienced haze, but those patients did not experience a decrease in best corrected vision.

“It looks like a sort of mild PRK haze,” Dr. Slade said. “The manufacturing process is being reviewed to see what we can do about that.”

Regarding efficacy, Dr. Slade said some eyes lost a few lines of best corrected vision. At this stage, the results are comparable to LASIK, he said. Phase 2 trials of the implant are expected to begin soon.

“Hopefully, this will be a tool to give us the ability to correct a greater range of hyperopia,” Dr. Slade said.