Keratoconus
What is Keratoconus?
The cornea is the clear outer layer of the eye that refracts light onto the retina, creating an image that the brain processes. The cornea’s surface is smooth and round in the center, gradually flattening towards the edges. Keratoconus is a condition where the shape of the cornea becomes cone-shaped, leading to an irregular corneal surface that results in distorted vision. This condition can cause visual difficulties such as blurred vision, increased sensitivity to light, and difficulty seeing at night. It can also lead to frequent changes in eyeglass or contact lens prescriptions and, in severe cases, may require surgical intervention.
Patients with keratoconus often require rigid contact lenses to correct vision due to the irregular, cone-shaped cornea. However, surgical options are available for those who cannot wear contacts. These options are discussed in the section on treatments for keratoconus. Patients with keratoconus may only realize they have the condition once they notice increased blurry vision or changes in their prescription. Even with a good refraction, they may still experience poor vision. A cornea specialist can diagnose keratoconus by examining the patient with a slit lamp. However, early forms of the disease may require corneal topography and/or computerized videokeratography for diagnosis.
Keratoconus typically begins during puberty and progresses until the mid-thirties. After that, progression usually slows or stops. It can advance or arrest anytime between ages 8 to 35 or older, and there is no way to predict how fast or if it will progress. Young patients with advanced disease are more likely to require surgical intervention. Keratoconus may initially affect only one eye, but it almost always affects both eyes, often to different degrees. Certain genetic factors are more common in certain regions worldwide.
Despite millions of dollars spent on research, the cause of keratoconus remains unknown. None of the theories have been conclusively proven. For example, one theory suggests deficient collagen cross-linking caused by free radicals. Still, there is no scientific evidence to definitely support such a theory. Others have indicated that eye-rubbing causes the progression of keratoconus. However, the proof of this is mostly based on several case reports. There needs to be reproducible scientific evidence to support this theory.
Our research group was the first to demonstrate that genetic factors play a significant role in the development of keratoconus (Wang Y, Rabinowitz YS, Rotter J, Yang H. Genetic epidemiological study of keratoconus: evidence for a major gene determination. American Journal of Medical Genetics 93:403-409; 2000). Although our scientific-based evidence supports a role for genetic factors, this does not mean that if you have a child with keratoconus, the child will necessarily develop the disease because only 13–15% of keratoconus patients have a family history of keratoconus. It does mean, however, that genes play a role in its development and that to provide a medical cure, the genes that contribute to the development of keratoconus must be identified and either replaced or suppressed. This is the only potential hope for a permanent cure to stop the progression of keratoconus and ensure the cornea will no longer continue to thin.