Scleral lens

Scleral lenses may be used to improve vision and reduce pain and light sensitivity for people with 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,[1] aniridia, neurotrophic keratitis (anesthetic 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.[2]

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.[3]

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 can become uncomfortable when worn for long periods of time and can 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 which are extremely popular for halloween and cosplay fancy dress costumes.

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.

Scleral lenses may be inserted into the eye directly from the fingers, from a hand held plunger, or from a stationary lighted plunger on a stand. Prior to inserting the scleral, the lens is over-filled with a sterile saline or other prescribed solution mixture. Some fluid is allowed to drip from the lens as it is inserted in order to ensure no bubbles become trapped under the lens after it is seated on the eye. If there is a bubble trapped then it is usually recommended to remove the lens and reinsert it. The lens can then be rotated to the correct orientation, often denoted by a mark at either the "top" or the "bottom" of the lens. A "left" scleral lens is often marked with two dots, and a "right" is marked with one dot. Less commonly, the "right lens" may instead be tinted blue to indicate "right".

Scleral lens prescribed for dry eye, on a removal plunger

Scleral lenses are removed using the fingers, or a small lens removal plunger. Lenses are then cleaned and sanitized before reinsertion. Scleral lenses cannot be worn while sleeping and many wearers sanitize their lenses overnight. Unlike regular contact lenses, many sclerals can be stored dry when unused for longer periods of time.