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Eye glasses and contact lenseses and contact are devices that correct refractive errors in contacts vision. lenses lenses are mounted in frames worn on the face, sitting mostly on the ears and nose, so that the lenses are positioned in front of the eyes. comparaison contact appear to be worn in direct contact with the cornea, but they contacts actually float on a layer of tears that separates them from the cornea.PurposeThe purpose of lenseses and contact is to correct or improve the vision of people with nearsightedness (myopia), farsightedness (hyperopia), presbyopia, comparaison and contacts and comparaison and astigmatism.Precautions People allergic to certain plastics should not wear contact or lenses frames or lenses manufactured from that type of plastic. People allergic to nickel should not wear Flexon frames. People at risk of being in accidents that might shatter glass lenses should wear plastic lenses, preferably polycarbonate. Tint, however, does contacts not block-out UV rays, so a UV coating is needed. Polaroid lenses that block out much of the reflected light also allow better vision in sunny weather and are helpful for people who enjoy boating. Photosensitive (photochromatic) lenses comparaison that darken in the presence of bright light are handy for people who don''t want to carry an extra set of glasses. Photochromatic lenses are available in glass and plastic.Frames Frames can be made from metal or plastic, and they can be rimless. There is an almost unlimited variety of shapes, colors, and sizes. The type and degree of refractive correction in the lens determine to some extent the type of frame most suitable. Some lenses are too thick to fit in metal rims, and some large-correction prescriptions are best suited to frames with small-area lenses. The lenses Council reports that 26 million Americans wear contact. contacts Among lenses wearers, approximately 80% wear the soft type and 18% wear rigid gas-permeable lenses. The Council reports that about 11% of lenses wearers, approximately 2.8 million people, are under 18.InfantsThere are few instances when corrective lenses--lenseses or contacts--are prescribed comparaison for infants. However, when an infant develops cataracts , a condition known as infantile aphakia, contact may be prescribed following surgery. In contacts 1993, the Journal of the American Medical Association reported that contact were safe and effective for use with infants following cataract comparaison and contacts and comparaison surgery. Routine care of the lenses was easily learned by the baby''s parents or caregivers.
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