Scleral lenses are an unusual type of contact lens that vaults the cornea altogether; its edges rest instead on the sclera (white of the eye), hence the name.
The primary purpose of scleral lenses is to address vision loss from certain cornea diseases. The lens holds a fluid layer over the cornea, which can correct many optical problems stemming from a deformed or damaged corneal shape. Keratoconus, a disease causing the cornea to gradually bulge, is the most common condition sclerals are used for.
But because of the liquid layer the lenses hold on the cornea, in recent years more work has been put into using them to treat ocular surface diseases.
Most of the research in this area has been done at Boston Foundation for Sight, who make custom lenses on-site for a variety of conditions. Please see PROSE for more details.