The cornea is the eye’s outermost layer. It is a clear, strong layer on the front of your eye. It helps protect your eye from dirt and germs. It also helps control how light enters your eye.

Some things can change your cornea’s shape. If your cornea has an abnormal shape, light rays don’t focus where they should. If this happens, you may have poor eyesight even when wearing glasses. A corneal ring implant helps flatten and reshape your cornea. This helps the light rays focus at the right place and makes your eyesight better. Some people may not need to wear eyeglasses after a corneal ring implantation. Others may still need to wear glasses. But their eyesight will be better.

You may need corneal ring implantation to treat poor eyesight caused by conditions such as:

• Keratoconus. This causes the cornea to become cone-shaped over time. Experts don't know why this happens.

• Pellucid marginal degeneration. This is a condition in which the cornea becomes too thin.

• Nearsightedness (myopia). If you have nearsightedness, you are not able to see things far away without the help of glasses or contact lenses. Nearsightedness is caused when the eyeball, cornea, or lens of your eye is the wrong shape. Corneal ring implantation may work best if you have mild or moderate nearsightedness. You might not need glasses or contact lenses after the surgery.

• Swelling of the cornea after eye surgery. LASIK surgery and radial keratotomy are 2 kinds of surgery to fix vision problems. After surgery, the cornea may swell. This can cause new eyesight problems. If this happens, your healthcare provider may advise corneal ring implantation to fix the vision changes.

Your procedure will be done by an eye surgeon. The surgery can be done in several ways. The surgeon will make small cuts in the outer edge of your cornea. He or she will make tunnels under the outer layer of your cornea. Sections of the ring are put into these tunnels. The cuts on the cornea are then closed with very small stitches (sutures).

All procedures have risks. Some of the risks of corneal ring implantation are:

• Swelling of the cornea

• Small hole (perforation) in the eye

• The ring poking out from the cornea (extrusion)

• Eye swelling

• Movement of the ring

• Halos (rings) around lights at night

• Seeing light as too bright (glare)

• Ongoing eye pain

• Infection

• Not much eyesight correction

• Causing another eyesight problem, such as astigmatism

• Need for an adjustment surgery

Your risks may differ based on your age, your health, and the condition of your cornea. Talk with your healthcare provider about which risks apply most to you.