|
By Roibeard O'hEineachain BARCELONA - The Permavision intracorneal lens (Anamed) appears set to provide an alternative to LASIK and phakic IOLs in the treatment of hyperopia and myopia if early clinical results are borne out in long-term clinical trials now underway. Of refractive procedures now available, LASIK has the advantages of being extraocular and easy to perform but it is irreversible. Phakic IOLs, on the other hand, are a reversible procedure but require intraocular surgery. The intracorneal inlays may be considered the best of both worlds because they offer an extraocular and easy to-perform procedure and are reversible, according to Dr Jose M Lemos MD, Hospital Santo Antonio, Porto, Portugal. In a series of six patients who received the inlays, three of five eyes with + 3.5 D to + 7 D hyperopia preoperatively were within (0.5D/1.0D) of emmetropia at a follow-up of one year. There was a slight but unimportant under-correction (1.5 D) in the two remaining hyperopic eyes. In the one eye with myopia (-9.0 D), there was a significant refractive error (-3 D), reported Dr Lemos in a presentation at the 6th ESCRS Winter Refractive Surgery Meeting. Complications included a slight downward displacement of the inlay. This appeared to be due to surgical methods and was not progressive. Among the hyperopes, BCVA remained unchanged in two eyes and two eyes lost one line of vision. The myopic patient lost three lines of BCVA. Some of the eyes had slight inferionasal decentrations. "The problems with this technique resulted mainly from the delivery system. Sometimes it was difficult to find the disc and sometimes the discs were put in upside down. This is probably what happened with the myopic eye. There is a now a new delivery system for the inlay that is much more user friendly and avoids the upside down discs," Dr Lemos explained. He said he has altered his technique, creating a larger 9.5 mm flap to avoid the decentration problem. He also now creates a nasal or inferior hinge because of concerns that the superior hinge was responsible for the dislocation of the disc. "This technique needs some improvements, mainly on the myope nomogram. This approach has good potential, but safety and efficacy must match LASIK and phakic IOLs before the technique will be widely used." The Permavision intracorneal inlays are composed of a highly permeable high-water content hydrogel with a refractive index almost identical to that of stroma. The implants have a disc shape. Those intended to treat hyperopia are 5 mm in diameter and can be used for the correction of refractive errors from +1 D to +6 D. Those intended for treatment of myopia are 7.0 mm in diameter, with a 2.0 mm central hole. They can be used to treat refractive errors from -5 D to -12 D. Implantation of the Permavision lens requires skills common to all LASIK surgeons. The surgeon first creates a flap with a microkeratome. After drying the disc and stroma to insure good adhesion, the flap is lifted. The surgeon then places the disc on the stroma, right side up and centred. The flap is then folded back over the lens. No sutures are required to keep the lens in place. The Permavision lens received the CE Mark and approval for commercial distribution throughout the European Union in 2001. The
lens also recently received FDA approval to conduct clinical trials
for the correction of hyperopia up to + 6 D. An international multi-centre
clinical trial is underway in 14 centres in 11 countries. |
