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(Lenses made from polycarbonate, the same type of plastic used for the space shuttle windshield, are about 50 times stronger than other lens materials.) Also, people at risk of receiving electric shock should avoid metal frames.People employed in certain occupations may be prohibited from wearing contact, or may be required to wear safety eyewear over the contact. Some occupations, such as construction or auto repair, may require safety lenses and safety frames. Physicians and employers should be consulted for recommendations. contacts Description for Eyes are examined by optometrists (O.D.) or by ophthalmologists astigmatism (M.D. or D.O.--doctor of osteopathy). Prescriptions, if necessary, are then given to patients for glasses. The glasses are generally made by an optician. A separate contacts lenses-fitting exam is necessary if the patient wants contact, because an lenses prescription is not the same as a lenses for and astigmatism prescription. The primary drawback to wearing contact, especially for children, is the requirement that they be cleaned and disinfected daily in order to prevent an infection, which could result in permanent damage to the eye. Careful choice of lenses and consistent lens care will minimize the risk of infection. Wearers of best lenses are the least prone to infection but the lenses are much less comfortable, more expensive, and can pop out of contacts the eye more easily than lenses. Daily wear lenses put the wearer at a slightly higher risk of infection because they absorb more external liquids for and airborne contaminants. They are flatter and lighter than conventional lenses.There are many lenses and lens-coating options astigmatism for individual contacts 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 for are particularly important on sunglasses and ski goggles. astigmatism 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 contacts that eliminate almost all glare and allow other people to see the eyes of the wearer. AR coatings for may be particularly helpful to people who use computers or who drive at night. Mirror astigmatism 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.
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