What Are Scleral Contact Lenses?
Scleral contacts are a large, rigid, gas permeable contact lens. They rest on the sclera, or “white” of the eye, rather than the corneal surface, like most contacts worn today. They are used to treat patients with conditions such as keratoconus, a condition that causes the cornea to steepen, which in turn causes corneal thinning, or irregularity in the cornea. The scleral lens helps to create a smooth, consistent surface.
Scleral contact lenses were the first contact lenses that were introduced and fit onto patients. The scleral lens was invented in the 1800's, and is believed to have been based on Leonardo DaVinci's experiments of submerging the eye in water, which affected corneal power. In 1889 Dr. August Mueller experimented with using ground glass lenses to correct his own vision. In the beginning, these lenses were extremely hard to fabricate, and did not allow enough oxygen in to keep the eye healthy.
In the 1900's, a new material called polymethylmethacrylate (PMMA) was used in the manufacture of scleral contact lenses. PMMA is a moldable plastic, that can be set into a rigid form. These lenses were still very difficult to make, and almost impossible to replicate if needed. Also, like its glass predecessors, PMMA lenses were not oxygen permeable, which did not keep the eye healthy enough for extended wear. An attempt was made to rectify the problem by putting small holes in the lense that allowed some air in. However, this caused extreme drying of the eye.
Even with the complications that could result from the wear of these early lenses, the 1920's saw doctors using standardized fitting sets in their offices. By the 1930's doctors were able to take a molded impression of the eye, and use that pattern to manufacture scleral contacts that were a more custom design for each patient. Now, scleral contacts are made out of a breathable material, and can be worn for several hours. The space behind the contact lens also holds fluid that prevents the eye from becoming too dry.
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