Keratoconus is an eye disorder marked by a progressive thinning of the cornea, or the outer layer of the eye that covers the lens and iris, causing the cornea to form a slight cone shape. This may result in blurry vision, double vision, nearsightedness, astigmatism, and light sensitivity. Usually both eyes are affected. In more severe cases a scarring or a circle may be seen within the cornea.
The cause is uncertain but is believed to be a combination of genetic, environmental, and hormonal factors. It occurs most commonly in late childhood to early adulthood and while it is seen in all populations it may be more frequent in ethnic groups of Asian descent.
It can be initially corrected with glasses or soft contact lenses, but as the disease worsens special contact lenses may be required. In most people the disease stabilizes after a few years without severe vision problems. In a small number of people scarring of the cornea occurs and a corneal transplantation is required.