Senile cataract, pictured here, may cause blindness by obstructing the passage of light. This most common form of cataract usually occurs in people over 50. The only treatment is extraction of the lens of the eye.

 Cataract (vision), in medicine, opaque condition of the lens of the eye or of its capsule. Its position behind the pupil readily distinguishes this condition from opacities of the cornea.

 Cataract may affect the lens alone (lenticular), or the front or back of the capsule of the lens (capsular), or both lens and capsule (capsulolenticular). Cataract is painless and unaccompanied by inflammation. It causes blindness by obstructing passage of light, but the patient can distinguish light from darkness.

 Traumatic cataract results from a perforating wound of the capsule of the lens. The entire lens becomes opaque, and a portion usually remains so; but at times, unless inflammation of other portions follows, the cloudiness entirely disappears. Congenital cataract is due to an intrauterine infection, chromosomal disorder, or metabolic disease that causes imperfect development or inflammation. Juvenile cataract may be hereditary. The lens is soft and white in both congenital and juvenile cataracts. Both are treated by “needling,” an operation in which a needlelike knife or a laser beam is used to cut and break up the lens. The injured lens tissue is then absorbed by the body. Juvenile and adult cataracts can also be caused by exposure to radiation and by drugs such as glucocorticoids.


 Surgery is usually required to restore full sight to individuals afflicted by cataract, a loss of transparency in the eye’s lens. The surgeon cuts into the cornea and snips off a piece of the iris, the round membrane that covers the lens and gives the eye its individual color. After this procedure, called an iridectomy, the natural lens is removed with a small pair of forceps and replaced by a new plastic lens. A fine suture is then used to close the incision in the cornea.

 Senile cataract, the most common form, usually occurs in people over 50 years of age and generally involves both eyes. It may also occur at a younger age in people with diabetes mellitus. Beginning in the form of dark streaks extending from the periphery toward the center of the lens, or as spots in any portion, it eventually makes the entire lens opaque. As the fluid of the lens is absorbed, the lens becomes easily separated from its capsule and is considered mature, or “ripe” for operation. Later, if not extracted, the lens undergoes degenerative changes, or liquefies, and the capsule becomes thickened and opaque, making the results of operation less satisfactory. The only method of relieving senile cataract is extraction of the lens. Sight can be restored in most instances by wearing special eyeglasses or contact lenses or by a surgeon implanting an artificial lens in the affected eye. Cataract removal is one of the most common surgeries in the United States, with over 1.5 million cataract surgeries performed each year. In about 90 percent of cases, people who have cataract surgery have better vision afterward.


 A cataract is a cloudy area in the lens of the eye. To a person with cataracts, the world appears hazy and out of focus. Cataracts can be successfully treated with surgery.