The following types of special lenses are available for specific situations:
Therapeutic contact lenses: In the presence of corneal erosion, soft ultra-thin (0.05 mm) contact lenses act as a bandage and thereby accelerate re-epithelialization of the cornea. They also reduce pain. Soft contact lenses may also be used in patients receiving topical medication as they store medication and only release it very slowly.
Corneal shields: These are collagen devices that resemble contact lenses. These shields are gradually broken down by the collagenase in the tear film. They are used as bandages and substrates for topical medication in the treatment of anterior disorders, such as erosion or ulcer.
Iris print lenses: These colored contact lenses with a clear central pupil are used in patients with aniridia and albinism.
They produce good cosmetic results, reduce glare, and can correct a refractive error where indicated.
Bifocal contact lenses: These lenses were developed to allow the use of contact lenses in presbyopic patients. As in eyeglasses, a near-field correction is ground into the lens. This near-field portion is always located at the bottom of the lens because the lens is heavier there. When the patient gazes downward to read, the immobile lower eyelid pushes this near-field portion superiorly where it aligns with the pupil and becomes optically effective. Another possibility is diffraction (bending of light rays as opposed to refraction) through concentric rings on the posterior surface of the contact lens. This produces two images, a distant refractive image and a near-field diffractive image. The patient chooses the image that is important at the moment. It is also possible to correct one eye for distance vision and the fellow eye for near vision (monocular vision).
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