Corrective Lenses

Individuals with severe visual impairment, such as the blind, often wear dark glasses to hide their eyes.

Corrective lenses can be made with UV protection, or secondary clip-on dark lenses can be placed in front of the clear corrective lenses to protect the wearer's eyes from the sun. Some corrective lenses slowly darken in bright light and lighten once the individual enters a building, or into a shaded area. These form of lenses are known as photo chromic, or transitional.

Individuals with severe visual impairment, such as the blind, often wear dark glasses to hide their eyes. Other individuals who are still sighted, but have severe visual impairment may also wear sunglasses to reduce glare.

Lenses are usually made from glass, acrylic, and polycarbonate. Glass lenses offer the best optical clarity, and scratch resistance, however, they are heavier than either acrylic, (plastic) or polycarbonate lenses and they can shatter or break on impact. Acrylic lenses are lightweight, and offer more resistance to shattering or breaking, however they are prone to scratching. Polycarbonate lenses weigh less than plastic lenses, are shatter-resistant and tend to resist scratches more.

The lens frames can be constructed from plastic, nylon, and a metal or metal alloy. Nylon frames are generally used in sports because of their lightweight and flexible. Metal frames are more rigid than nylon frames, however can be easily damaged when worn while participating in active sports. Because of this, many metal frames have spring-loaded hinges give them more flexibility and to help hold to the wearer's face.







 

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