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lensesesOver 140 million people in the United States wear lenseses. People whose eyes have refractive errors do not see clearly without glasses, because the light emitted from the objects they are observing does not come into focus on their retinas. For people who are farsighted, images come into focus behind the retina; for people who are nearsighted, images come into focus in front of the retina. Lenses work by changing the direction of light so that images come into focus on the retina. The greater the index of refraction of the lens material and the greater the difference in the curvature between the two surfaces of the lens, contacts the greater the change in direction comparison of light that passes through it, and the greater the correction.Lenses can be unifocal, with one correction for all distances, or they can be correct for more than one distance (multifocal). One type of multifocal, the bifocal, has an area of the lens (usually at the bottom) that corrects for nearby objects (about 14 in from the eyes); the remainder of the lens corrects contacts for distant objects (about 20 ft from the eyes). They are flatter and lighter than conventional comparison lenses.There are contacts many lenses and lens-coating options for individual needs, including coatings that block the ultraviolet (UV) light or UV and blue light which have been found to be harmful to the eyes. Such coatings are not needed on polycarbonate lenses, which already have UV protection. UV coatings are particularly important on sunglasses and ski goggles. Sunglasses, when nonprescription, should be labeled with an indication that they block out 99-100% of both UV-A and UV-B rays. There are anti-scratch coatings that increase the surface hardness of lenses (an important feature when using plastic lenses) and anti-reflective (AR) coatings that eliminate almost all glare and allow other people to see the eyes of the wearer. AR coatings may be particularly helpful to people who use computers or who drive at night. Mirror coatings that prevent other people from seeing the wearer''s eyes are also available. There is a whole spectrum of tints, from light tints to darker tints, used in sunglasses. One, he didn''t think they were available from any other source," "and two, he had heard they weren''t as highly controlled as those dispensed through comparison doctors."Neither assertion is true. got on the Internet and found her lenses on several Web sites for $35.95 for a box of six pairs. (Her doctor was charging contacts $50 a box.) says her doctor told her that lenses offered by places like may have failed manufacturers'' quality checks. Bausch contacts and other lensmakers say there''s no difference in quality between the lenses sold through doctors and those sold directly to consumers. STATES CRACK DOWN. Attorneys general in 32 states have sued the American Optometric Association and two of the top contact-lens manufacturers comparison (Vistakon, a division of contacts, and Bausch), alleging that the AOA tried to get manufacturers to agree to selllenses only through optometrists or other eye-care professionals. The attorneys general contacts say they also have evidence that doctors agreed to withhold prescriptions from people who sought to buy lenses from other sources, despite the fact that at least 22 states have comparison laws requiring eye doctors to give out contact-lens prescriptions upon request.Although the AOA says patients should be able to buy their lenses anywhere, the organization has reservations about mail-order purchases. "The difficulty when someone goes through mail order is that they don''t come back for regular checkups," says AOA president contacts Dr. Harvey Hanlen comparison.
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