Keratoconus is a slowly progressive eye condition that affects the clear, front surface of the eye – the cornea. The normally round, dome-shaped cornea weakens and thins, causing a cone-like bulge to develop. The regular curvature of the cornea becomes irregular, resulting in increasing nearsightedness (myopia) and astigmatism that have to be corrected with specialty contact lenses. Since the cornea is responsible for refracting (bending and focusing) most of the light coming into the eye, corneal abnormalities can result in significant visual impairment, making simple tasks like driving or watching TV difficult.
Keratoconus is estimated to occur in one out of every 2,000 persons in the general population. Generally, it is first diagnosed in young people at puberty or in their late teens. There is no known significant geographic, cultural or social pattern.
What causes keratoconus?
The cause of keratoconus is unknown. It may be caused by:
- an inherited corneal abnormality; about seven percent of those with the condition have a family history of keratoconus or high astigmatism;
- excessive eye rubbing
- long-term rigid contact lens wear
Keratoconus usually affects both eyes, although one eye is usually more severely affected. The progression of the condition is generally slow and can stop at any stage from mild to severe. In its earliest stages, keratoconus causes slight blurring and distortion of vision and increased sensitivity to glare and light. Glasses and contact lens prescriptions may change frequently. As the condition advances, vision decreases even with the best possible glasses or contacts. Thinning and scarring of the cornea worsens in the advanced stages.
In most cases, eyeglasses or soft contact lenses are used to correct the mild nearsightedness and astigmatism that is caused in the early stages of keratoconus. As the disorder progresses and the cornea continues to thin and change shape, rigid, gas permeable contact lenses are prescribed to correct vision more adequately. The contact lenses must be custom fitted. Frequent checkups to observe the status of the cornea and to monitor changes in the corrective lenses are needed to achieve and maintain good vision.
Recently, there have been exciting new treatments for newly diagnosed keratoconics. Corneal cross linking is a treatment that creates additional chemical bonds inside the cornea by means of photopolymerization. This technique adds some strength to the cornea and has been showing a consistent stabilizing effect on the cornea. Intracorneal ring segments that are implanted in the cornea can also help to reduce the astigmatism and provide better visual acuity with contact lenses.
With individuals who have had keratoconus a long time and (were not able to have corneal cross linking) a corneal transplant may be needed due to scarring, extreme thinning or contact lens intolerance. This surgical procedure replaces the misshapen cornea with healthy donor corneal tissue that is sutured in place.