December 17, 1999
A small, plastic implant can allow some people with low-level nearsightedness to say good-bye to glasses.
The implant, called a corneal ring, can be inserted during a half-hour outpatient procedure. Doctors make a diamond-shaped incision in the periphery of the cornea (the front part of the eye that refracts light), push aside tissue, then implant the ring two-thirds deep. The position of the implant causes the central curvature of the cornea to flatten, thereby correcting the nearsightedness.
Corneal rings are an alternative to the now-popular LASIK (laser assisted in situ keratomileusis) procedure, a refractive surgery in which nearsightedness is corrected by removing a thin layer of corneal tissue. They are recommended for people with mild nearsightedness, those who mainly rely on glasses to drive or to see well at night. LASIK is recommended for people with more severe nearsightedness.
"The key advantage with the corneal rings is they're removable," says Terrence P. O'Brien, M.D., director of refractive surgery at Hopkins' Wilmer Eye Institute. "If the patient's sight changes as they get older, the implants can be taken out, and the corneal tissue is elastic enough that it returns to its original shape."