A cataract is an opacity, or clouding, of the lens in the eye. The opacity can cause blurred vision and eventual blindness. Light enters the eye through the cornea, which is the transparent covering of the eyeball. Then the light passes through the lens, which bends the light onto the retina at the back of the eye. In an eye with a cataract, light can no longer pass through the clouded part of the lens. Cataracts are often associated with aging and are thus called "senile cataracts." They can also be caused by diabetes, parathyroid gland abnormalities, Down's syndrome, and other medical conditions. Recent studies suggest that exposure to the ultraviolet radiation in sunlight and artificial light during childhood may have an effect on the formation of cataracts in later life.
Cataract surgery has a long history. It was mentioned in the code of Hammurabi, a Babylonian king who lived 4,000 years ago. The first known cataract operation to extract a clouded lens was performed by J. Daviel, a Frenchman, in 1748. Another well-known surgeon, W. Cheselden, restored sight to a man born blind.
In a surgical procedure called an introcapsular extraction, the entire lens is removed through a cut made along the top edge of the cornea. In this surgery, invented by an American named Kelman in 1976, an ultrasonic device actually emulsifies (breaks) the lens into tiny fragments so that it can be aspirated (suctioned) from the eye. A plastic lens is then inserted, and the incision is closed with tiny sutures. Plastic lenses were first invented in 1952 by the English physician Harold Ridley. The plastic lens may completely restore vision, or the patient's vision may require fine-tuning with additional eyeglasses or contact lenses.
In 1905 Austrian physician Eduard Zirm performed the first known corneal transplant (the removal of an object or organ from one body to another) by transplanting the cornea of one person into the eye of a blind person. Basing his work on Zirm, Dr. Elschwig of Prague, Czechoslavakia, also successfully performed a corneal transplant in 1914. Since 1944, eye
In 1961, an American physician, Irving S. Cooper, began using a freezing technique known as cryosurgery to freeze and destroy damaged tissue. Cooper first used cryosurgery on the damaged brain tissue of Parkinson's disease (a progressive nervous system disorder) patients. Now it is successfully used to remove cataractous lenses. In 1979 Professor Daniele Aron-Rosa performed the first laser eye surgery to use the ultra-rapid, pulsated Yag laser. Lasers allows surgeons to work without having to cut the eye. Laser surgery has also been successfully used on corneas and detached (unattached) retinas.