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 sfxtheatricaldiscocontactlens 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, the greater the change in direction 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 for distant objects (about 20 ft from the eyes).

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 sfxtheatricaldiscocontactlens 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, the greater the change in direction 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 for distant objects (about 20 ft from the eyes).

Preschool and school-age childrencontact are a significant improvement over lenseses for children sfxtheatricaldiscocontactlens and adolescents who participate in sports or outdoor activities.contact are recommended for most athletes who need corrective eyewear. Often, a single pair of lenses is less expensive than the combined cost of glasses and prescription goggles. Swimmers especially can benefit from being able to see underwater while wearing regular goggles over their contact. Because contact tend to dry the eye, swimmers and all athletes should take care to blink several times before and after an activity session in order to assure natural cleansing. If any pool water enters a swimmer''s eyes, the lenses should be thoroughly disinfected as soon as possible to remove pool contaminants. Children who like spending time looking into a telescope, microscope, or binoculars may also prefer contacts over lenseses.