Keratoconus is a degenerative, progressive disorder of the eye in which structural changes within the cornea cause it to thin and change to a more conical shape than its normal round shape. Keratoconus can be difficult to detect, because it usually develops so slowly but may proceed rapidly in some cases. It usually develops during the teen years. As the cornea becomes more irregular in shape, it causes progressive nearsightedness and irregular astigmatism to develop, creating additional problems with distorted and blurred vision. Glare and light sensitivity also may be noticed. Keratoconic patients often have prescription changes every time they visit their eye care practitioner. If keratoconus is suspected, then a corneal topography will be done to confirm the diagnosis.
New research suggests the weakening of the corneal tissue that leads to keratoconus may be due to an imbalance of enzymes within the cornea. This imbalance makes the cornea more susceptible to oxidative damage from compounds called free radicals, causing it to weaken and bulge forward.
Risk factors for oxidative damage and weakening of the cornea include a genetic predisposition, explaining why keratoconus often affects more than one member of the same family. Keratoconus is also associated with overexposure to ultraviolet rays from the sun, excessive eye rubbing, a history of poorly fit contact lenses and chronic eye irritation.
Eyeglasses or soft contact lenses may be used to correct mild nearsightedness and astigmatism that is caused by the early stages for keratoconus. As the disorder progresses and the cornea continues to thin and change shape, rigid gas permeable contact lenses can be prescribed to correct vision adequately. In most cases, this is adequate. The contact lenses must be carefully fitted, and frequent checkups and lens changes may be needed to achieve and maintain good vision. In a few cases, a corneal transplant is necessary. However, even after a corneal transplant, eyeglasses or contact lenses are often still needed to correct vision.