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2. List of soft contact lens materials | Wikipedia

   en.wikipedia.org/wiki/List_of_soft_contact_lens...

   The first contact lenses were made of glass, in 1888. Initially the glass was blown but soon lenses were made by being ground to shape. For the first fifty years, glass was the only material used. The lenses were thin, yet reports of injury were rare. In 1938 perspex (polymethylmethacrylate, or PMMA) began to replace glass in contact lens ...

3. Prism correction | Wikipedia

   en.wikipedia.org/wiki/Prism_correction

   Prism dioptres. Prism correction is commonly specified in prism dioptres, a unit of angular measurement that is loosely related to the dioptre. Prism dioptres are represented by the Greek symbol delta (Δ) in superscript. A prism of power 1 Δ would produce 1 unit of displacement for an object held 100 units from the prism. [2]

4. Refractive error | Wikipedia

   en.wikipedia.org/wiki/Refractive_error

   One style is hard contact lenses, which can distort the shape of the cornea to a desired shape. Another style, soft contact lenses, are made of silicone or hydrogel. Depending on the duration they are designed for, they may be worn daily or may be worn for an extended period of time, such as for weeks. [32] There are a number of complication ...

5. Esotropia | Wikipedia

   en.wikipedia.org/wiki/Esotropia

   Esotropia (from Greek eso 'inward' and trope 'a turning' [ 1 ]) is a form of strabismus in which one or both eyes turn inward. The condition can be constantly present, or occur intermittently, and can give the affected individual a "cross-eyed" appearance. [ 2 ] It is the opposite of exotropia and usually involves more severe axis deviation ...

6. Esophoria | Wikipedia

   en.wikipedia.org/wiki/Esophoria

   Esophoria is an eye condition involving inward deviation of the eye, usually due to extra-ocular muscle imbalance. It is a type of heterophoria.

7. Vertex distance | Wikipedia

   en.wikipedia.org/wiki/Vertex_distance

   Vertex distance is the distance between the back surface of a corrective lens, i.e. glasses (spectacles) or contact lenses, and the front of the cornea. Increasing or decreasing the vertex distance changes the optical properties of the system, by moving the focal point forward or backward, effectively changing the power of the lens relative to ...