- The earliest eyeglass lens, which was formed out of 1 1/2 inches of polished rock crystal, was found in the ruins of the ancient city of Nineveh in Assyria. In about 1000 C.E., the "reading stone," or what today is called the magnifying glass, was used to make it easier for the farsighted monks to read. These scholars did not have bifocals as most people do today for close-up work. Later, the Venetians made magnification lenses that were put in a frame to wear over the eyes rather than holding it right over the reading material.
- When you look at something, the light rays come together, or focus, inside your eye. The retina, made up of cells that react to this light, lies at the back of the eye. This retinal reaction is transmitted to the brain, which translates the cellular activity into an image, or what you see. When someone has perfect vision, the rays focus directly on the surface of the retina. The image shrinks and curves to match the curved shape of the retina. The pupil and cornea have the job of shrinking, focusing and curving the image. Your vision will be blurry if the pupil or cornea are irregular in any way. In nearsighted individuals, who do not clearly see distant objects, the light rays focus in front of the retina. In farsighted people, who do not see close objects, the rays focus behind the retina.
- The corrective eyeglass lens is curved and bends the light rays in the right direction, so you can clearly see images. The goal of the correction is having the focal point hit the retina in just the exact place for ideal vision. Convex lenses, slightly curved in, are used for nearsighted people. They bend the rays toward the top and bottom of the lens and push the focal point back toward the retina. Concave lenses, which bend the light toward the center, are for farsighted individuals. The degree of the lens' curve changes with the prescription's strength. Your eyesight does not change for good, but does correct itself with the use of these lenses. The same holds true for the traditional contact lenses.
- With newly developed contact lenses, or orthokeratology, you can actually change your eyesight for the short term without wearing any corrective lenses. Before you go to sleep, you put on special contact lenses that reshape your eye's surface. For a day or two, you can actually have near perfect eyesight without glasses or contacts.
- In the most recently developed laser eye surgery, the cornea is reshaped to alter the way light rays enter the eye. In laser-assisted in situ keratomileusis (LASIK), a thin, hinged flap is made in the surface of the eye. The flap is then lifted and the laser used for reshaping. The flap is finally replaced and acts as a natural bandage.
- Photorefractive keratectomy or PRK is an alternative when LASIK is not feasible. The is refractive error correction for nearsightedness, farsightedness, astigmatism and presbyopia. Similar to LASIK, the treatment requires about a minute per eye. Instead of making a flap, a sterile brush is used to scrape away cells. Then the laser reshapes the cornea. This may take longer to heal and cause more discomfort.
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