Why it happens: Glaucoma, a disease that causes optic nerve damage, has no symptoms until much of the optic nerve is dead. After that, the first symptom is often the loss of peripheral vision.
How to Fix it: Once an optic nerve fiber dies, there is no way to bring it back. "The goal of glaucoma treatment is to prevent the loss of additional nerve fibers," says Galbraith. Glaucoma is actually a family of diseases, so treatment will depend on the type and may include medication or surgery.
Red Flag: Because glaucoma has no symptoms until it is fairly advanced, don't neglect a glaucoma screening at your next eye exam.
Why it happens: Blame it again on the lens, which gets cloudy with age (a clouded lens is a cataract). "A lot of people don't realize it because it's a gradual process. Things may turn more yellow or brown than they really are," says Brian Bonanni, M.D., medical director of Gotham Lasik Vision in New York City.
How to Fix it: A surgeon can remove the cataract and replace it with a permanent, plastic lens. Cataracts are typically repaired one eye at a time, several weeks apart, to allow the surgical eye to heal. If you're not ready for surgery but notice a color change, your doctor may suggest yellow-tinted glasses, which can help brighten your surroundings.
Red Flag: If left untreated, cataracts can lead to blindness, so see your doctor.
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