What is a cataract?
A cataract is an eye disease in which the normally clear lens of the eye becomes cloudy or opaque, causing a decrease in vision. The natural lens of the eye focuses light onto the back of the eye (the retina) so images appear clear and without distortion. The clouding of this lens during cataract formation causes blurring and distortion of vision. Cataracts are usually a very gradual process of normal aging but can occasionally develop rapidly. They commonly affect both eyes, but it is not uncommon for a cataract in one eye to advance more rapidly. Cataracts are very common, especially among the elderly.
Precisely why cataracts occur is unknown. However, most cataracts appear to be caused by changes in the protein structures within the natural lens that occur over many years and cause the lens to become cloudy. Rarely, cataracts can present at birth or in early childhood as a result of hereditary enzyme defects, other genetic disease, or systemic congenital infections. Severe trauma to the eye, eye surgery, or intraocular inflammation can also cause cataracts to develop more rapidly. Other factors that may lead to development of cataracts at an earlier age include excessive ultraviolet light exposure, exposure to ionizing radiation, diabetes, smoking, or the use of certain medications, such as oral, topical, or inhaled steroids. Other medications that may be associated with cataracts include the long-term use of statins and phenothiazines.
The total number of people who have cataracts is estimated to increase to 30 million by 2020. When people develop cataracts, they begin to have difficulty doing activities they enjoy. Some of the most common complaints include difficulty driving at night, reading, watching television or movies, and recognizing faces. These are all activities for which clear vision is essential.