The eye's lens is a clear structure that focuses images on the light-sensitive retina. A cataract is a clouding of the lens. This distorts or blocks the passage of light through the lens, causing cloudy or blurred vision, other visual problems, and even blindness. The name cataract comes from the term for "huge waterfall," which is how some people describe their clouded sight: like trying to look through a waterfall.
It usually takes years for the clouding of the lens to keep light from reaching the retina or distorting light rays.
Cataracts are usually an age-related condition. They first appear in the 40s or 50s, but may not affect vision until much later. Some cataracts are caused by an injury to the eye, long-term diabetes, the use of corticosteroid medications, or radiation treatment.
Some babies are born with cataracts, or develop them because of an infection that happened during pregnancy, such as toxoplasmosis, cytomegalovirus, syphilis, rubella, or herpes simplex. In infants and young children, cataracts also can be one symptom of a disease that affects how the body processes carbohydrates, amino acids, calcium or copper.
Cataracts are the world's leading cause of blindness, accounting for half of all cases of blindness.
Symptoms of cataract
Cataracts typically do not cause any symptoms until they have grown large enough to interfere with vision. Symptoms include:
- cloudy or blurry vision
- double vision
- colors appear faded
- seeing halos around lights
- increased sensitivity to glare
Your story of your visual symptoms is an important part of diagnosing cataract. Your eye doctor will likely widen (dilate) your pupils with medication and examine your eyes, and give you a visual acuity test to check your vision.
People with cataracts can use eyeglasses, magnifying lenses, or stronger lighting to help improve their vision. But the only way to cure a cataract is with surgery. Before going ahead with surgery, it's important to weigh how bad your vision is against the small risk of surgery and the likelihood that it will improve your vision.
Cataract surgery involves removing the clouded lens and replacing it with a plastic lens inserted in the eye during surgery.
Cataract surgery improves the vision of most — but not all — people who have it. In some people, the surgery causes posterior capsule opacification, in which the part of the eye behind the artificial lens becomes cloudy. This can be corrected with laser surgery.