Word: corneas
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...Contact lenses are not ideal either: often difficult to manage, uncomfortable to wear, easy to lose. Is there any other option? Some ophthalmologists now think there is. They say two common vision problems-near- and farsightedness (myopia and hyperopia)-can be corrected or eased with surgery that reshapes the cornea, the eye's outer covering...
Light enters the eye in parallel rays, which are gradually bent as they pass through the cornea and lens. In the normal eye, they converge, or focus, precisely on the retina at the back of the eyeball. Electrical impulses then transmit a sharp image to the brain. In the nearsighted, however, the eyeball is usually too long or the cornea too curved, so that the rays come to a focus in front of the retina. In the farsighted, the eyeball is too short or the cornea too flat and the light rays, if they could pass through it, would converge...
...correct these conditions would be to change the curvature of the cornea so the images fall directly on the retina. The pioneer of surgery that accomplishes that optical feat is Ophthalmologist José Barraquer of Bogotá, Colombia, who for the past two decades has been performing a variety of delicate and complex corneal operations that he calls refractive keratoplasty (an operation on the cornea for optical reasons). In one procedure known as keratomileusis (cornea carving), the front of the cornea is sliced off with a high-speed vibrating blade, quickly frozen, and then reshaped on its underside...
...still newer and more controversial corneal operation was developed by Soviet Ophthalmologist Svyatoslav Fyodorov. In 1973 he examined a nearsighted 16-year-old youth whose glasses had been smashed in a fight. The shards had cut the cornea of one eye. Three days later the boy could see perfectly out of the eye-without glasses. The injury had inadvertently flattened the cornea...
...operation that was inspired by the accident, a procedure called radial keratotomy (a cut or slice into the cornea), the surgeon makes 16 or so incisions into the cornea. The cuts, varying in length and depth, extend from the outer edge of the cornea toward the center like spokes of a wheel. The internal eye pressure will stretch the nicked regions, thus flattening the center of the cornea...