Contact lenses are used for vision correction and are placed a propos the cornea of the eye. They reach the same corrective take effect that adequate spectacles, or glasses, make a attain of. However, in comparison, they are highly well-ventilated in weight and are, for all purposes, invisible. Contact lenses by now form the image re the retina of the eye by either converging or diverging the rays of roomy entering the eye.
Earlier quirk in lenses were made of glass, and were scleral lenses. Scleral lenses are large entry lenses that lid the unlimited idea sclera – the white outer coating – of the eye. These unwieldy lenses could by yourself be worn for a immediate epoch at a times. With the build occurring of PPMA – polymethyl methacrylate – in the 1930s, plastics were first used in confront lenses. These were in fact, hybrid scleral lenses, made following the doings of both, glass and plastic, in 1936.
By the 1950s, much smaller admission lenses were developed that covered only the cornea of the eye and not the mass eye.
