What is a cataract?

A cataract is a progressive clouding of the lens of the eye that result in a decrease in vision. In the picture on the right, the pupil should be black, but a cataract is causing the haze. The diagram illustrates where in the eye cataracts form. Cataracts are very common. In fact, everyone will get a cataract if they live long enough. In that sense a cataract is considered more “normal aging” than a disease.


What causes cataracts?

Cataracts are caused by oxidative damage to lens cells, which cause them to change from clear to cloudy. Oxidative damage normally occurs in the cells of our body, which leads to other aging changes we all experience. Oxidative change can be hastened by UV light exposure (the harmful sun rays that burn skin and promote skin cancer), and a diet poor in anti-oxidants. Genetics can play a role in early cataract development; in fact some people are born with a cataract. A cataract can be associated with certain medications, like Prednisone, and certain diseases, like diabetes. Inflammatory disorders of the eye, like Iritis or Uvietis, can cause cataracts. Still another cause of cataracts may be trauma to the eye.


What are the symptoms of a cataract?

It is common to compare the function of the eye to a camera. The eye’s lens focuses light onto the retina in the back of the eye; much like a camera’s lens focuses light onto the film. A cataract blocks light from entering the eye, causing the vision to be blurry, like if the lens of a camera was blurry. Other common symptoms of a cataract include glare and halos around lights at night, difficulty seeing in the dark, double “shadow” vision, and impaired vision in bright light.

Examples of common functional effects of cataracts would include difficulty seeing to drive, especially in unfamiliar areas when it is necessary to read road signs. It can become difficult to engage in some hobbies, like seeing to aim a rifle, or follow a golf ball. Some people are concerned about not being able to read smaller print on the TV, like game scores or news type. Night vision, with glare, can be very bothersome, limiting driving. Sometimes bright light on a sunny day, on a lake, or sun through a window can degrade vision. Detailed near activities, like threading a needle or stitching, can become difficult. Reading grey-on-grey type, like small newspaper print, can be impaired.


Can cataracts be prevented?

At this time there is no effective preventive therapy for cataracts. There is some evidence from population studies that antioxidant vitamins and UV blocking sunglasses may slow a cataract’s growth.