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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 ocularsciencebiomedics38&55contacts 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. Description Eyes are examined by optometrists (O.D.) or by ophthalmologists (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 lenses-fitting exam is necessary if the patient wants contact, because an lenses prescription is not the same as a lenses prescription. Planned-replacement lenses are daily wear lenses that are replaced on a regular schedule, which is usually every ocularsciencebiomedics38&55contacts two weeks, monthly, or quarterly. They must also be cleaned. Soft contact come in a variety of materials. ocularsciencebiomedics38&55contacts There are also different kinds of RGP and soft multifocal contact available. Monovision, where one lenses corrects for distance vision while the other corrects for near vision, may be an option for presbyopic patients. Monovision, however, may affect depth perception and may not be appropriate for everyone. contact also come in a variety of tints. corrective are available that can change dark-colored eyes a different color. Even though such lenses ocularsciencebiomedics38&55contacts have no prescription, they must still be fitted and checked to make sure that an eye infection does not occur. People should NEVER wear someone else''s contact. This can lead to infection or damage to the eye. Aftercarelenses wearers must be examined periodically by their eye doctors to make sure that the lenses fit properly and that there is no infection. Both infection and lenses that do not fit properly can damage the cornea. Patients can be allergic to certain solutions that are used to clean or lubricate the lenses. ocularsciencebiomedics38&55contacts For that reason, patients should not randomly switch products unless they speak with their doctor. contact The concept of corrective lenses that sit directly on the eyeball was developed in the ninth century, but it was not until the late 20th century that manufacturing and grinding techniques for contact were perfected. Originally contact were made of glass, then later of hard plastic, and still later of flexible, highly oxygen-permeable soft plastic. Today, the ocularsciencebiomedics38&55contacts majority of lenses worn are of two basic types: rigid gas permeable (so-called "hard" lenses) and lenses. best lenses are smaller and more durable, ocularsciencebiomedics38&55contacts but require a longer period of adjustment for the wearer. Hard ocularsciencebiomedics38&55contacts contact can correct some vision problems, like astigmatism, that the lenses cannot. The lenses are slightly larger than best lenses. They are more comfortable and less expensive, but can be easily torn. The latest generations of contact are extended and disposable lenses. extended lenses are intended to be worn for several weeks at a time, while disposable lenses are thrown away every day or every few weeks, or in the newest versions, every day.
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