Contact lenses are used for vision correction and placed in the cornea of the eye. They do the same corrective function that conventional spectacles, or glasses, do.
However, in comparison, they are very light and, for all purposes, invisible. Contact lenses help form the image on the retina of the eye by either converging or diverging light rays entering the eye. If you're looking for a regular contact lens in Toronto, you can browse various online sources.
Previously contact lenses are made of glass and scleral lenses. Scleral lenses are large contact lenses that cover the complete sclera – the white outer coating of the eye.
These heavy lenses could only be worn for short periods at a time. With the development of PPMA – polymethyl methacrylate – in the 1930s, plastics were first used in contact lenses. In fact, hybrid scleral lenses, made with a combination of both, glass and plastic, in 1936.
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In 1950, much smaller contact lenses were developed that covered only the cornea of the eye and not the whole eye.
Type of Vision Impairments
One of the major uses of contact lenses is to correct visual defects. The general disorder is Myopia, Hyperopia, Astigmatism, and Presbyopia.
Myopia – is a visual defect in which the image of the object seen is formed in front of the retina. During this visual impairment, we can see objects that are near, and not the distant objects, which appear blurred. This defect also is known as nearsightedness.
Hyperopia – It is also known as hyperopia, and the image of the object is formed behind the retina. Far objects can be seen clearly, and close objects seem blurred. Hyperopia is more commonly known as nearsightedness, and more than 13 percent of children in the United States, in the age group of 5 to 17 suffer from it.
Astigmatism – This occurs when the lens of the eye has more than one focal point, in different meridians. astigmatic people can not see in fine detail and need cylindrical lenses to correct their damage. Nearly 34 percent of American children in the age group of 5 to 17 have the disorder.