Specialty Contact Lenses
Specialty contact lenses are for patients that either don't qualify for soft contact lenses or glasses, or specifically need special lenses for their vision. They come in a wide variety of options and in most cases can be fully covered by insurance.
Overview
Arguably the most common type of specialty contact lenses are scleral lenses, which are hard, large contact lenses that don't touch the cornea and only sit on the white part of the eye (the sclera, hence "scleral lenses"). Other options include rigid gas permeable (RGPs), which were one of the first contact lenses, also a hard lens but much smaller and typically not as uncomfortable. Hybrid lenses which are hard in the center and soft on the edges. Custom soft lenses which are the same material as soft lenses but the prescription is custom made for the patient. And cosmetic lenses for patients that have a misshapen iris, scarred cornea, or other irregularity.
Keratoconus
Keratoconus means "cone-shaped cornea", and happens because the cornea gets so thin that the fluid inside of it pushes it outwards. This causes the astigmatism to get so severe that patients see everything as double, smeared, extremely blurry, and are extremely light sensitive. For these patients, glasses and soft contact lenses simply can only do so much for vision, and in some cases aren't even good enough to drive legally. Scleral lenses can restore vision to 20/20 in certain cases!
Dry Eye
When it seems like none of your dry eye treatments are working, scleral lenses are FDA approved for the treatment of Dry Eye Syndrome and Ocular Surface Disease. Because they're filled with sterile saline and suction to the cornea, that saline stays on your eye all day, providing constant moisture - think constantly flowing artificial tears.
Post RK/LASIK
When refractive surgery didn't turn out as you hoped, sometimes your vision can be worse than when you started, and even glasses and soft contact lenses won't work to correct vision anymore. Scleral lenses usually work best for these scenarios, because the fluid you fill them with can fill in the irregularities of your cornea.
High Astigmatism
When your astigmatism is so high that glasses or traditional soft contact lenses just don't provide you clear, crisp, sharp vision, there are still options. Custom soft contacts, RGPs, or sclerals can all do a good job of correcting high amounts of astigmatism.