Scleral contacts are large-diameter, gas permeable contact lenses specially designed to vault over the entire corneal surface and rest on the "white" of the eye (sclera). In doing so, scleral lenses functionally replace the irregular cornea with a perfectly smooth optical surface.  This corrects vision problems caused by keratoconus and other corneal irregularities.

The space between the cornea and the back surface of a scleral lens acts as a fluid reservoir to provide comfort for people with severe dry eyes who otherwise could not tolerate contact lens wear.