Four natural "defenders" protect your eye: the eyelid, a thin lining called the conjunctiva, the cornea (a clear covering over the front of the eye), and tears. But sometimes bacteria, viruses, or a foreign substance get past these defenses, and your eye becomes infected. You may be able to treat the problem at home. But if the infection is serious, you'll need medical care right away to save your vision.

The three most common eye infections are conjunctivitis (or pink eye), marked by pus or watery discharge and crust on the eyelashes; sties, pimplelike growths at the base of eyelashes; and blepharitis-red, scaly skin on the eyelids. None are serious diseases. But they may be painful and sometimes chronic, meaning you get them again and again for months or years.

You can prevent eye infections by keeping your hands clean and keeping them away from your eyes, and by not sharing washcloths. You can also avoid substances that make your eyes itch, water, or burn. If you already have an eye infection, you and your doctor can cure it and try to keep it from coming back.