Cataract
A cataract is a clouding of the eye's natural lens, which lies behind the iris and the pupil. Cataracts are the most common cause of vision loss in people over age 40 and is the principal cause of blindness in the world. In fact, there are more cases of cataracts worldwide than there are of glaucoma, macular degeneration and diabetic retinopathy combined, according to Prevent Blindness America (PBA).
Glaucoma
Glaucoma refers to a group of eye disorders that usually have few or no initial symptoms and eventually cause harm to the optic nerve that carries information from the eye to the brain.