Cataract is a progressive clouding of the eye lens. Every person will one day go on to develop a cataract if he or she gets old enough. Some people develop a cataract at the age of 45, others at 85. This depends primarily on how much ultraviolet light the eye has been exposed to in the course of life, and especially in youth. People from sun-rich countries, such as those around the Mediterranean sea, often develop a cataract in their mid-fifties. Cataract is therefore not a disease, but a natural symptom of aging.
A healthy lens is clear, but in a cataract, the lens of the eye gradually becomes harder as well as cloudier, allowing less light to pass, making it harder to see. If we compare the natural lens with the lens of a camera, one can say that the lens is severely scratched and clouded. The result is a bad, blurry and cloudy image.
Although relatively easy to remedy by surgery, cataract is the most common cause of blindness in the world, as in poorer countries most people can not afford such an operation.