Corneal Inlays and Onlays
Corneal inlays and onlays are small lenses or optical devices that can be inserted into the cornea to alter its shape and correct vision problems.
In LASIK and PRK, vision correction is achieved by removing corneal tissue with a laser to reshape the eye. But with corneal inlays or onlays inserted just beneath the surface of the cornea, laser energy can be used to sculpt this artificial material instead of the eye itself, and corneal thickness can be preserved.
Corneal inlays and onlays work much like contact lenses, but with the advantage of never needing removal or ongoing care. And they differ from intraocular lenses, or IOLs, because they are less invasive and aren’t placed in the interior of the eye (behind the cornea or iris).
And because corneal inlays and onlays don’t require tissue to be removed from the cornea, there may be less risk of ectasia (bulging of the cornea), dry eye and other potential complications of laser vision correction procedures like LASIK and PRK.
The Corneal Inlay Procedure
With some corneal inlays, a pocket is created in the eye’s surface. The inlay is then inserted into the opening and positioned in the center of the cornea. With other inlays, a flap is created (as in LASIK), the inlay is placed on the cornea, and the flap is put back into place over it.
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.
The Corneal Onlay Procedure
Corneal onlays are positioned under the cornea’s thin outer layer of cells called the epithelium. An instrument is used to create a pocket between the epithelium and the stroma, and the onlay is inserted in this space. The onlay is secure nearly immediately, and within 48 hours, new epithelial cells grow over the surgical wound to seal it completely.
When Will These Procedures Be Available in the U.S.?
Most of these devices and the surgical procedures associated with them are not yet FDA-approved for use in the United States, but they are undergoing clinical trials.
One exception is the Kamra corneal inlay by AcuFocus, which was FDA-approved in April 2015 to improve near vision for people with presbyopia. Kamra was approved for patients aged 45-60 who have prescriptions of +.50 D to -0.75 D (meaning they have practically no refractive error) with a near correction need of +1.00 D to +2.50 D of reading add.
Clinical trials are ongoing for two other corneal inlays designed to correct presbyopia.