Word: corneas
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Dates: during 1990-1999
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...eyes are surrounded by a tough, protective layer called the sclera. Only at the front of the eyeball does the sclera give way to the cornea, which is transparent. Light passes through the cornea to the pupil, the hole in the middle of the iris, or colored part of your eye. Depending on how bright the incoming light is, the pupil grows wider or narrower, much like the adjustable aperture of a camera. The light then passes through the lens, which lies directly behind the iris and changes shape as needed--curving or flattening--to help focus the image onto...
...happens, the eye's lens provides just a third of the eye's focusing power. The rest comes from the cornea, which acts like a second lens to help focus light onto the retina. If you're nearsighted, or myopic, your eye produces clear images of nearby objects or people. But light from distant sources is focused on a point somewhere in front of your retina--either because the curve of your cornea is too steep relative to the length of your eyeball, or the eyeball is too long relative to the corneal curve. If you're farsighted, or hyperopic...
Attempts to change the way the cornea focuses light by surgically altering its surface began as early as the 1950s. By the 1970s Soviet doctors routinely used scalpels to reshape the corneas of nearsighted patients in an operation called radial keratotomy. But the surgery, involving a spokelike ring of incisions, never really caught on in the U.S., because the results were so difficult to predict and the healing process was often slow and painful...
Salome is explaining a traditional cure for pterygium, an eye affliction common to the tropics in which vision gradually becomes obscured as a layer of tissue encroaches over the cornea. The traditional cure used by healers is leaves of Centella asiatica, a ground-hugging vine, which Salome chews into a poultice, smears on a cloth and then places as a compress on the afflicted eye for three consecutive nights...
Patients fill the lens--which is about the sizeof a quarter--with a lubricant, which in turnfills the space between the lens and the eye,providing lubrication to the irritated cornea andallowing the patient to see normally...