Eyeglasses and Contact Lenses (Encyclopedia of Children's Health)
Eyeglasses and contact lenses are devices that correct refractive errors in vision. Eyeglass lenses are mounted in frames that are worn on the face, sitting mostly on the ears and nose, so that the lenses are positioned in front of the eyes. Contact lenses appear to be worn in direct contact with the cornea, but they actually float on a layer of tears that separates them from the cornea.
The purpose of eyeglasses and contact lenses is to correct or improve the vision of people with nearsightedness (myopia), farsightedness (hyperopia), presbyopia, and astigmatism.
Eyes are examined by optometrists (OD) or by ophthalmologists (MD or DO). Prescriptions, if necessary, are then given to patients for glasses. Eyeglasses are generally made by an optician. A separate contact lens-fitting exam is necessary if an individual wants contact lenses, because an eyeglass prescription can differ from a contact lens prescription.
More than 140 million people in the United States wear eyeglasses. People whose eyes have refractive errors...
(The entire section is 2770 words.)
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