Some types of cataracts are associated with heredity, certain diseases such as diabetes, long-term usage of some medications and overexposure to ultraviolet light. (You should aim for maximum elimination of UV light in sunglasses.) Senile cataracts are generally considered to be part of the aging process, which causes the lens of the eye to dry out and become clouded.

Cataract comes from the word cataracta, Latin for waterfall, which is how many patients describe the cloudy or opaque area in the lens of the eye. The National Eye Institute lists these signs that you may have a cataract, but stresses that they do not necessarily mean you have a cataract and/or that it must be removed:

* Hazy, fuzzy or blurred vision. Double vision sometimes occurs, but this usually goes away as the cataract worsens.

* The appearance of dark, fixed spots in the field of vision.

* The need for frequent changes in eyeglass prescriptions. Beyond a certain progression of the cataract, the changes no longer improve vision.

* A feeling of having a film over the eyes; a lot of blinking in an effort to see better.

* Changes in color of the pupil.

* Problems with finding the right amount of light, or night driving.

* "Second sight," a temporary vision improvement that is lost as the cataract progresses.

Among sources of more information:

* National Eye Institute, Office of Scientific Reporting, Bethesda 20205. Provides public information on cataracts and other eye diseases, as well as new research advances.

* National Society to Prevent Blindness, 79 Madison Ave., New York 10016.

* Cataracts: A Consumers' Guide to Choosing the Best Treatment ($3.50, 110 pp.) by Robert B. Leflar and Helen Lillie. Available from Health Research Group, Dept. 35, 2000 P St. NW, Washington, D.C. 20036.