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Corneal Inlays and Onlays are More Like a Contact Lens than a lens Implant
Corneal inlays and onlays are more like a contact lens than a lens implant. Still in clinical trials, corneal inlays and onlays are being investigated as a treatment for presbyopia and may have potential for other refractive errors, as well. Presbyopia occurs naturally with aging. Different theories of its cause suggest that it involves either or both the thickening and stiffening of the natural crystalline lens. Another possible cause is weakening of the ciliary muscle that bends the lens. One more theory suggests that the lens continues to grow beyond a functional size. These minimally invasive procedures involve inserting either the corneal inlay or onlay under a thin flap near the surface of the eye, or on top of the cornea. In contrast, other implantable lenses are surgically placed under the cornea. Corneal Inlays
Under study since 2006 is the AcuFocus ACI 7000. This small micron thick disk, made of a thermoplastic material, uses a pinhole opening to concentrate focus through a small aperture. This improves clear vision at near, intermediate and distance vision. The inlay is inserted under a thin layer of corneal tissue near the top of the cornea. Other manufacturers also have inlay lenses in clinical trials. ReVision Optics is testing the PresbyLens 2mm diameter inlays. This inlay is inserted into a pocket or under a thin flap. It steepens the cornea’s dome shape, increasing near and intermediate vision. Patients tested after six months showed at least 20/25 distance vision and most did not need corrective lenses for reading or computer use. A third product under study in Europe is the Presbia Flexivue System. The lens is slipped in place through a tiny pocket just under the surface of the eye. The procedure can be reversed, or the lens removed if a stronger prescription replacement lens needs to inserted. While corneal inlays show have shown great promise and success outside of the United States, there are, apparently, some issues with halos that are still being worked out. Corneal Onlays
Despite the similarity in names corneal onlays take a different approach to correcting presbyopia. This procedure is still in experimental stages. The onlay is made of a genetically developed human collagen-type substance. The epithelium is removed and the recombinant collagen is injected into a tiny pocket. Still under study are ways to keep this collagen in place until the epithelial cells grow back and seal the collagen material in place. This material can be shaped with laser surgery to refine any refractive error, and without altering the natural layers of the cornea. Still to Come
Both corneal inlays and onlays have yet to be FDA approved as both procedures and devices in the United States. Corneal onlay clinical trials have not even begun, yet. Corneal inlays have been used successfully in other countries for quite some time. For example, Francisco Sánchez Leon, M.D. of Mexico City has been using the InVue corneal inlay from Biovision AG for many years. He reported that those patients who had corneal inlays placed five years prior still had clear vision. While it may be some time before your local ophthalmologist can offer corneal inlays in the U.S., if you’re in a hurry, eye surgeons in Mexico City already have years of experience and many success stories with this procedure. |