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contact The concept of corrective lenses that sit directly on the eyeball was developed in the ninth century, but it contacts 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. eyes Today, the contacts 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, but require a longer period of adjustment for the wearer. Hard contact can correct some vision problems, like astigmatism, that the lenses eyes 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 contacts 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. Preschool and school-age childrencontact are a significant improvement over lenseses for children and adolescents who participate in sports or outdoor activities.contact eyes 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 contacts pool contaminants. Children who like spending time looking into a telescope, microscope, or binoculars may also prefer contacts over lenseses. The distance between the lenses is eyes for a "standard" person. Generally, this will contacts not be a problem, but if a patient is sensitive or has more closely set eyes, for example, it may pose a problem. Persons buying ready-made sunglasses or reading glasses should hold them up to see if they appear clear. They should also hold the lenses to see an object with straight lines reflected off of the lenses. If the lines don''t appear straight, the lenses may be warped or inferior.Patients may sometimes need a few days to adjust to a new prescription; however, problems should be reported, because the glasses may need eyes to be rechecked.contact
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