A daily wear contact lens is designed to be removed prior to sleeping. An extended wear (EW) contact lens is designed for continuous overnight wear, typically for 6 or more consecutive nights. Newer materials, such as silicone hydrogels, allow for even longer wear periods of up to 30 consecutive nights; these longer-wear lenses are often referred to as continuous wear (CW). Generally, extended wear lenses are discarded after the specified length of time. These are increasing in popularity, due to their obvious convenience. Extended- and continuous-wear contact lenses can be worn for such long periods of time because of their high oxygen permeability (typically 5-6 times greater than conventional soft lenses), which allows the eye to remain healthy.
Regular contact lenses cover only the colored part of your eye, the iris, but sclera lenses are much larger and also cover the white part of your eye, the sclera. For this reason, we urge you to see an optometrist for a proper fitting before you order sclera contact lenses. Your unique eyes may or may not be suited to wearing this type of lens.During the early stages of this disease, vision may still be correctable to 20/20 with glasses. The only clue to a keratoconus diagnosis may be from corneal measurements or a corneal topography map (see maps to the right). A topographical map of the cornea will show the high and low spots on the cornea, much like a topographical map of the earth will show the mountains and oceans.