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Contact lenses, or simply contacts, are thin lenses placed directly on the surface of the eyes. Contact lenses are ocular prosthetic devices used by over 150 million people worldwide, and they can be worn to correct vision or for cosmetic or therapeutic reasons.
soft contact lenses; rigid gas-permeable (RGP) daily wear; extended wear; disposable; planned replacement contact lenses. The US Food and Drug Administration (FDA) defines soft contact lenses as: made of soft, flexible plastics that allow oxygen to pass through to the cornea.
A collection of telephoto lenses. A telephoto lens, also known as telelens, is a specific type of a long-focus lens used in photography and cinematography, in which the physical length of the lens is shorter than the focal length.
A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses ( elements ), usually arranged along a common axis.
Oxygen permeability (OP) is a parameter of a contact lens that expresses the ability of the lens to let oxygen reach the eye by diffusion. In soft contact lenses, it is dependent on the thickness of the lens and the material of the lens, especially concerning the water content.
Astigmatism causes difficulties in seeing fine detail. Astigmatism can be often corrected by glasses with a lens that has different radii of curvature in different planes (a cylindrical lens), contact lenses, or refractive surgery. Astigmatism is quite common. Studies have shown that about one in three people suffers from it.
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