If you’re in your forties or fifties, you probably know someone who has cataracts. That’s because while cataracts can occur at any age (in fact, babies can be born with them), they are most common later in life. About 75% of people in the United States over age 60 have some signs of cataracts. An estimated 20.5 million Americans over age 40 (approximately 17%) had a cataract. That number is expected to reach 30.1 million by 2020. Cataract surgery is the most commonly performed surgical procedure in the United States. More than 1.5 million cataract operations are performed each year.
A cataract is an opacification (cloudiness) of the eye’s normally clear crystalline lens. Derived from the Latin word meaning “waterfall,” the term cataract arose from the ancient misconception that cataract symptoms were caused by evil liquids that mysteriously flowed into the eye.
The cause of most cataracts is unknown, but at least two factors associated with aging contribute to cataract development:
- First, clumping of proteins in the lens leads to scattering of light and a decrease in the transparency of the lens.
- Second, the breakdown of lens proteins leads to the accumulation of a yellow-brown pigment that clouds the lens.
Researchers have found certain chemical changes in the eyes of people with cataracts. These changes include a reduced uptake of oxygen by the lens and a rise in the water content of the lens, which is later followed by dehydration. When cataracts form, levels of calcium and sodium in the lens increase, and levels of potassium, vitamin C, and protein decrease. In addition, lenses with cataracts appear to be deficient in the antioxidant glutathione. However, studies on the use of medications or vitamins to alter the levels of these substances in the lens have not produced promising results. Currently, there is no effective drug therapy to prevent cataracts from forming. But cigarette smoking, certain drugs, eye injuries, sunlight, diabetes, and even obesity can increase the risk of cataracts.
Cataracts form painlessly. The most common symptom is cloudy or blurry vision. Everything becomes dimmer, as if seen through glasses that need cleaning. Most often, both eyes are affected, though vision is usually worse in one eye than in the other. Other symptoms include glare, halos, poor night vision, a perception that colors are faded or that objects are yellowish, and the need for brighter light when reading.
In some cases, double vision occurs. This is caused by the passage of light through a lens that has irregular areas of opacity, which can split the rays of light from a single object and focus them on different parts of the retina. Another symptom of cataracts is the need for frequent changes in eyeglass and contact lens prescriptions. These symptoms can develop rapidly (in a matter of months) or almost imperceptibly, over many years.
