A scleral lens is a type of contact lens. The lens is much larger than the typical contact lenses that many people wear today. Unlike the typical contact lens that rests over the cornea of the eye, the scleral lens rests over the cornea and on the sclera of the eye. While a cornea lens may measure about 0.35 inches (9.0 mm) to about 0.37 inches (9.5 mm) in diameter, a full scleral lens can measure as wide as about 0.94 inches (24.0 mm), which is about the diameter of a United States quarter. Scleral lenses enable people with certain eye conditions to see when traditional corrective methods and eye treatments have failed.
The scleral lens was actually the first contact lens to be invented, dating back to 1888. A German glass manufacturer designed the enlarged lens from glass to help him with his vision problems. The lenses were weighty, uncomfortable and deprived the eye of oxygen, and so the idea for a scleral lens disappeared. By the 1950s, gas permeable, plastic polymer corneal lenses were developed, and these became the primary contact lenses for most wearers.
Unfortunately, some people cannot wear typical corneal corrective lenses. Those with bulging, thinning, irregularly shaped or damaged corneas cannot wear typical contact lenses. Since scleral contacts do not rest on the corneal but on the sclera, or white portion, of the eyeball, the result is better vision and improved comfort.
Scleral lenses have allowed patients suffering from keratoconus, corneal surgery and other eye diseases to see again. The unique lens does not touch the cornea of the eye, but rather floats above it and grasps the sclera for support. To prevent the eye from drying out or becoming irritated, the lens is filled with a sterile saline liquid before being inserted onto the eye. People who wear scleral contacts mention improved comfort as well as improved vision, as the lens never touches the sensitive cornea to cause them irritation.
Each scleral lens is custom fitted for each eye for every patient. The patient is first rigorously tested for any existing and underlying eye diseases. An initial trial lens and fitting are scheduled before the final product is ordered and fitted. Patients may discover that inserting a scleral lens is actually easier than inserting a tiny corneal lens, and the scleral lens is less likely to pop out of the eye. As with corneal lenses, scleral contacts are manufactured of gas-permeable plastic material and need to be replaced regularly.