Scleral contact lenses are large-scaled gas permeable lenses, mostly used for those patients who have an irregular cornea shape, including those with keratoconus. These are specifically designed to vault over the entire corneal surface and rest on the white portion of the eye, also known as the sclera. This allows for the lens to replace the irregular cornea shape with a perfectly smooth optical surface and correction of visual problems. Sizes of scleral lenses vary. The smallest sclerals are approximately 14.5 mm in diameter, and the largest can be up to 24 mm, whereas most traditional GP lenses are 9.0 to 9.5 mm and only cover 75% of the cornea. Because scleral lenses are designed to vault the corneal surface and rest on the less sensitive surface of the sclera, these lenses are often more comfortable for a person with keratoconus. In addition, scleral lenses are designed to fit with little or no lens movement during blinks, making them more stable on the eye, compared with traditional gas permeable lenses.
Scleral lenses are a good choice for not only patients with keratoconus, but also those experiencing difficulties after LASIK or any other corneal refractive surgery.