The cornea, the clear covering over the front of the eye, normally has a dome shape. When keratoconus develops, the dome-shaped part of the cornea thins, causing it to become cone shaped. Because the cornea refracts light, any change in its shape impacts vision. Keratoconus causes worsening nearsightedness and astigmatism, an imbalance that makes things look tilted. Keratoconus affects 5 out of 10,000 people and occurs slightly more frequently in women. There are three types of keratoconus.
Puberty-Onset Keratoconus
Puberty-onset keratoconus, the most common type of the disease, normally begins to develop between ages 14 and 16. Both eyes are affected, although one is usually worse than the other, and the disease progresses rapidly for the next 8 to 10 years, the Pacific University of Oregon School of Optometry reports. The younger the age at the time of diagnosis, the more severe the disease over time. Different types of contact lens strategies may help puberty-onset keratoconus, including "piggybacking," or wearing two different contacts at the same time, hybrid contacts, which have a rigid center and a soft peripheral area and scleral contacts, which cover the sclera, the white part of the eye. Corneal transplant may be necessary if contacts can't be worn or are ineffective.
Late-Onset Keratoconus
Late-onset keratoconus develops in the late 20s, 30s or beyond and affects both eyes equally. As in puberty-onset keratoconus, the earlier the diagnosis, the further the diseases progresses. Late-onset keratoconus is, overall, less severe than puberty-onset disease, according to the Pacific University of Oregon. Treatment for late-onset keratoconus is similar to that for puberty-onset keratoconus.
Keratoconus Fruste
Keratoconus fruste, also called form fruste, is a mild form of the disease that doesn't progress over time and can develop at any age. The cornea doesn't thin in this form of the disease, but astigmatism and topographical changes in the cornea similar to those found in other forms of keratoconus occur, according to the 2007 Global Keratoconus Congress. Rigid gas-permeable contact lenses are often adequate to improve vision in keratoconus fruste.
