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Corneal implants intended for insertion beneath the epithelium
The highly porous implants, now in animal trials, may be a reversible, nonablative means of vision correction.
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SYDNEY, Australia – A novel method of inserting a contact lens just below the epithelium is in animal clinical trials here, in an effort to provide an effective yet reversible method of vision correction.
The corneal onlay is a contact lens designed to be inserted just beneath the epithelium to provide stable yet reversible refraction. Patients could potentially have less visual downtime than with LASIK and improved long-term stability of refractive correction, the device’s developers say.
Brien A. Holden, PhD, director of the Cooperative Research Centre for Eye Research and Technology (CRCERT), said the onlay could tap into the market of patients currently seeking vision correction by LASIK and extended-wear contact lenses.
To insert the onlay, the epithelium is removed and the onlay placed on the underlying tissue. The epithelium then regrows, incorporating the inlay into the corneal tissue as part of the normal wound-healing response.
“It is a relatively quick and simple procedure to place a lens superficially,” Dr. Holden said. “Such a superficial procedure does no permanent damage to the cornea or to the eye, as it does not involve penetration of the anterior chamber. Additionally, it will be an in-office procedure.”
The lens could be removed or replaced as the refractive needs of the patient changed with time. The lens could also be used to replace scarred or diseased corneal tissue. This would eliminate the problems of limited supply, tissue rejection and infection associated with corneal transplants.
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Novel material
The onlay is made from a highly porous perfluoropolyether that is isorefractive with corneal tissue. The correction in refractive error is achieved by the change in curvature of the anterior corneal surface. The first-generation CRCERT Implantable Lens will offer a range of correction from –6 D to 6 D, with astigmatic and possibly presbyopic applications in the future.
“The procedure is the simplest, easiest and most reversible of all potential refractive surgery procedures. It should be predictable and very optically accurate,” Dr. Holden told Ocular Surgery News.
No laser is required, the procedure does not ablate tissue, it does not interfere with the structural integrity of the eye and it does not risk long-term corneal ectasia.
“At worst it might need to be removed and/or another one implanted with only the epithelium to have to regrow,” he said.
Oxygen permeability is very important for the internal eye, and the material developed has extremely high oxygen permeability, Dr. Holden said. The permeability is achieved with unique, sponge-like lenticles.
“These amazing materials also have their surface topography designed so that the basal layer of the epithelium will invade the surface of the lenticle, synthesizing the attachment fibrils and plaques to anchor the epithelium. Perhaps even more important is that we have researched, defined and patented the permeability needed through the onlay to supply the epithelium with the aqueous-derived metabolites essential to its health,” he said.
The polymer must be biocompatible with the surrounding tissue, as well as encourage and sustain a functioning epithelium to grow over the implant. The implant will maintain this compatibility for at least 10 years. If the patient requires their prescription to be updated, it would be a simple procedure to remove the implant and replace it. Currently the candidate polymer is being tested and could enter human trials in 2 or 3 years.
For Your Information:
- Brien A. Holden, PhD, director of the Cooperative Research Centre for Eye Research and Technology (CRCERT), can be reached at Level 4, North Wing, Rupert Myers Building, Gate 14 Barker Street, UNSW, Sydney 2052, Australia; (61) 2- 9385-7418; fax: (61) 2-9485-7401; e-mail: Brien@crcert.unsw.edu.au.