What is Cataract?   Cataract is a clouding of the part of the eye called the lens, which is normally transparent. Cataracts are not a disease, but rather a condition affecting the eye. As the natural lens of the eye becomes cloudy, it does not allow light to pass through it as well as it did when it was transparent. If left untreated, cataracts can cause needless blindness.   Symptoms of Cataract    Cloudy, fuzzy, foggy, or filmy vision. Changes in the way you see colors. Problems driving at night because headlights seem too bright. Problems with glare from lamps or the sun. Frequent changes in your eyeglass prescription. Double vision. Better near vision for a while only in farsighted people. These symptoms also can be signs of other eye problems.   How is a Cataract Diagnosed?   A regular eye exam is all that is needed to find a cataract. Your eye care professional will ask you to read a letter chart to see how sharp your sight is. You probably will get eye drops to enlarge your pupils (the round black centers of your eyes). This helps the doctor to see the inside of your eyes. The doctor will use a bright light to see whether your lenses are clear and to check for other problems in the back of your eyes.   Other eye tests may also be used occasionally to show how poorly you see with a cataract or how well you might see after surgery:   Glare test. Contrast sensitivity test. Potential vision test. Specular photographic microscopy. Only a few people need these tests. Can Cataracts be prevented?   Most of the cases of cataract occur as an aging process and the exact cause is not known. In some families cataract tend to occur at an earlier age. Cataract can also set in following an injury to the eye or as a part of systemic disease or conditions such as diabetes.  Traumatic cataracts may result from an injury or blow to the eye. Other causes of cataracts include the use of certain drugs or medications, exposure to harmful chemicals or excessive sun light, and some diseases. Some infants are born with congenital cataracts. In some cases, cataracts may even develop during childhood.   Can a Cataract Return?   A cataract cannot return because all or part of the lens has been removed. However, in some people who have had extracapsular surgery or phacoemulsification, the lens capsule becomes cloudy after a year. It causes the same vision problems as a cataract does. To correct this, laser capsulotomy can be performed. In laser (YAG) capsulotomy a laser (light) beam is used to make a tiny hole in the capsule to let light pass. This surgery is painless and does not require stay in the hospital.   What should I know about Cataract Surgery?