Keratoconus is a degenerative disease of the cornea that causes it to gradually thin and bulge into a cone-like shape. This shape prevents light from focusing precisely on the macula. As the disease progresses, the shape becomes more pronounced, causing blurred or distorted vision. Patients with keratoconus are usually very nearsighted because of the cornea's irregular shape and have a high degree of astigmatism that is not correctable by glasses.
Keratoconus usually occurs in both eyes and is characterized by symptoms such as blurred vision (even when wearing glasses or contact lenses), glare at night, light sensitivity, frequent prescription changes or eye rubbing. Generally, this disease is diagnosed by the time patients reach their 20's. Because keratoconus is not usually visible to the naked eye, special testing is used for a detailed look at the shape of the cornea.
The first line of treatment for patients with keratoconus is to fit rigid gas permeable contact lenses. Because this type of contact is not flexible, it creates a smooth, evenly shaped surface to see through. However, because of the cornea's irregular shape, specialty contact lenses are often required. If vision deteriorates to the point that contact lenses no longer provide adequate vision, a corneal transplant may be necessary to replace the diseased cornea with a healthy one.