Corneal inlays and onlays are made of biocompatible materials that closely resemble the clear surface of the eye itself. And if current and future clinical trials prove successful, these devices may soon represent a new form of vision correction surgery.
In LASIK and PRK, vision correction is achieved when laser energy reshapes the cornea to alter the way light rays enter the eye. But with corneal inlays or onlays inserted just beneath the eye’s surface, laser energy some day could be used to sculpt this artificial material instead of the eye itself.
Even without laser reshaping, corneal inlays or onlays alone also may work much like contact lenses to provide vision correction. Unlike contact lenses, however, these devices never require regular removal or ongoing care. And they differ from surgically implanted lenses because they are not placed behind the cornea. Also, a corneal inlay or onlay is designed to seamlessly “merge” with the eye’s surface.
Through use of inlays and onlays for vision correction, eye surgeons may avoid complications sometimes associated with procedures such as LASIK, PRK, and implantable lenses because the eye’s natural surface tissue is left virtually undisturbed.
While the technology is not yet approved by the FDA, clinical trials began in early 2006 for one device created by AcuFocus (Irvine, Calif.), which has formed a business alliance with Bausch & Lomb (Rochester, N.Y.).
The ACI 7000 is a corneal inlay used for presbyopia correction. (Image provided by AcuFocus of Irvine, Calif.)
This corneal inlay, known as the ACI 7000, is designed to correct near vision focusing problems caused by aging, a condition known as presbyopia. With this inlay, a thin flap is created on the eye’s surface where the device is applied. The flap then is replaced over the inlay to hold it in place.
The procedure takes less than 15 minutes and can be performed in the eye surgeon’s office. Sutures are not required, and only topical anesthesia in the form of eye drops is used. According to Bausch & Lomb, the inlay is designed to block certain light rays reflecting from near objects that ordinarily would not be focused correctly by the presbyopic eye.
“Its optical principle is the pinhole phenomenon, which when used in photography (in terms of a small aperture), allows depth-of-focus and thus allows clear vision at all distances – near, intermediate, and distance.