Cataracts
Although half the people over age 50 and three-quarters of those over age 75 develop cataracts, the condition isn't an inevitable part of aging. Cataracts are cloudy patches or areas in the lens inside your eye. Recent studies show that certain lifestyle strategies can lessen your chance of developing this serious but treatable vision disorder.
What It Is
The eye's lens is normally transparent; it allows light to pass through to the back of the eye, which allows a clear image to form.
One eye can often be more affected than the other. When the proteins in the lens break down, they clump together and form opaque spots called cataracts. The cloudier the lens becomes, the more your sight will be affected and vision becomes cloudy or blurry. The degree of impaired vision depends on the cataract's size, density, and location on the lens.
Symptoms 
- Gradual and painless blurring or dimming of vision.
- Increased sensitivity to sun glare or car headlights at night
- Seeing halos around lights
- Changes in color perception.
What Causes It
Cataracts may develop as a result of age-related body changes; but some experts now think that the majority of cases can be attributed to smoking or to lifetime exposure to ultraviolet (UV) light from the sun. A low level of antioxidants (vitamins C and E, beta-carotene, and selenium) may also be a factor. These compounds can squelch free radicals - unstable oxygen molecules - that can damage the lens. (Normally, the lens has a high concentration of glutathione, an antioxidant produced by the body). Having diabetes or being overweight increases the risk of cataracts, probably because high levels of sugar (glucose) in the blood contribute to the destruction of lens proteins. Injury to the eye can cause cataracts too.
What Else You Can Do 
- Quit smoking.
- Protect your eyes from UV rays by wearing sunglasses and a wide-brimmed hat when outdoors
- Eat plenty of fresh fruits and vegetables; they're good sources of antioxidants.
Cataracts are the leading cause of blindness in the world.
Although cataracts have no scientifically proven prevention, it is sometimes said that wearing ultraviolet -protecting sunglasses may slow the development of cataracts.