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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. Contact lens - Wikipedia

    en.wikipedia.org/wiki/Contact_lens

    Two main strategies exist: multifocal lenses and monovision. Multifocal contact lenses (e.g. bifocals or progressives) are comparable to spectacles with bifocals or progressive lenses because they have multiple focal points. Multifocal contact lenses are typically designed for constant viewing through the center of the lens, but some designs do ...

  4. Progressive lens - Wikipedia

    en.wikipedia.org/wiki/Progressive_lens

    Progressive lenses are corrective lenses used in eyeglasses to correct presbyopia and other disorders of accommodation. They are characterised by a gradient of increasing lens power, added to the wearer's correction for the other refractive errors. The gradient starts at the wearer's distance prescription at the top of the lens and reaches a ...

  5. Multifocal diffractive lens - Wikipedia

    en.wikipedia.org/wiki/Multifocal_diffractive_lens

    Multifocal diffractive lens. A multifocal diffractive lens is a diffractive optical element (DOE) that allows a single incident beam to be focused simultaneously at several positions along the propagation axis. [1] Example of multifocal peak intensity distribution along optical axis. (Courtesy of Holo/Or)

  6. Effects of long-term contact lens wear on the cornea - Wikipedia

    en.wikipedia.org/wiki/Effects_of_long-term...

    Long-term contact lens use can lead to alterations in corneal thickness, stromal thickness, curvature, corneal sensitivity, cell density, and epithelial oxygen uptake, etc. Other changes may include the formation of epithelial vacuoles and microcysts (containing cellular debris) as well as the emergence of polymegethism in the corneal endothelium.

  7. Presbyopia - Wikipedia

    en.wikipedia.org/wiki/Presbyopia

    Presbyopia is a typical part of the aging process. [4] It occurs due to age related changes in the lens (decreased elasticity and increased hardness) and ciliary muscle (decreased strength and ability to move the lens), causing the eye to focus right behind rather than on the retina when looking at close objects. [4]

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