Scleral lens

A scleral lens, also known as a scleral contact lens and ocular surface prostheses is a large contact lens that rests on the sclera and creates a tear-filled vault over the cornea. Scleral lenses are designed to treat a variety of eye conditions, many of which do not respond to other forms of treatment. A scleral lens, also known as a scleral contact lens and ocular surface prostheses is a large contact lens that rests on the sclera and creates a tear-filled vault over the cornea. Scleral lenses are designed to treat a variety of eye conditions, many of which do not respond to other forms of treatment. Scleral lenses may be used to improve vision and reduce pain and light sensitivity for people suffering from a growing number of disorders or injuries to the eye, such as severe dry eye syndrome, microphthalmia, keratoconus, corneal ectasia, Stevens–Johnson syndrome, Sjögren's syndrome, aniridia, neurotrophic keratitis (aneasthetic corneas), complications post-LASIK, higher order Aberrations of the eye, complications post-corneal transplant and pellucid degeneration. Injuries to the eye such as surgical complications, distorted corneal implants, as well as chemical and burn injuries also may be treated by the use of scleral lenses. Sclerals may also be used in people with eyes that are too sensitive for other smaller corneal-type lenses, but require a more rigid lens for vision correction conditions such as astigmatism. Scleral lenses are not to be confused with 'sclera' lenses, which are soft lenses and do not contain a fluid reservoir. 'Sclera' contacts are used in movies such as the whited-out eyes of the monsters in Evil Dead, or blacked-out eyes in Underworld and Underworld: Evolution, or the Star Trek episode Where No Man Has Gone Before. These lenses tend to be uncomfortable and sometimes impede the actors' vision, but the visual effects produced can be striking. These lenses can be custom-painted, although most companies only sell lenses with a pre-designed look. In experiments in ophthalmology or cognitive science, scleral lenses with embedded mirrors or with embedded magnetic field sensors in form of wire coils (called scleral coils) are commonly used for measuring eye movements. Modern scleral lenses are made of a highly oxygen permeable polymer. They are unique in their design in that they fit onto and are supported by the sclera, the white portion of the eye. The cause of this unique positioning is usually relevant to a specific patient, whose cornea may be too sensitive to support the lens directly. In comparison to corneal contact lenses, scleral lenses bulge outward considerably more. The space between the cornea and the lens is filled with artificial tears. The liquid, which is contained in a thin elastic reservoir, conforms to the irregularities of the deformed cornea, allowing vision to be restored comfortably. This helps to give the patient BCVA, or Best Corrected Visual Acuity. Scleral lenses differ from corneal contact lenses in that they create a space between the cornea and the lens, which is filled with fluid. The prosthetic application of the lenses is to cover or 'bandage' the ocular surface, providing a therapeutic environment for managing severe ocular surface disease. The outward bulge of scleral lenses and the liquid-filled space between the cornea and the lens also conforms to irregular corneas and may neutralize corneal surface irregularities.