KeratoconusKeratoconus is a non-inflammatory, progressive ectasia of the cornea. It is characterized by progressive thinning and steepening of the central cornea into a cone-like shape. As the cornea steepens and thins, the patient experiences a decrease in vision, which can be mild or severe depending on the degree to which corneal tissue is affected.
Onset of keratoconus occurs during the teenage years-mean age of onset is age 16 years-but onset has been reported to occur at ages as young as 6 years. Keratoconus rarely develops after age 30. Keratoconus shows no gender predilection and is bilateral in over 90% of cases. In general, the disease develops asymmetrically: diagnosis of the disease in the second eye lags about five years after diagnosis in the first. The disease process is active for about five to 10 years, and then it may be stable for many years. During the active stage, change may be rapid.
Typically, vision loss can be corrected early by glasses or soft contact lenses; later, due to the abnormal shape of the cornea and the onset of increased myopia and irregular astigmatism, rigid (hard) contact lenses are required for optical correction and functional vision. Contact lenses provide a uniform refracting surface to improve the patient's vision, while at the same time they work to support the bulging cornea. Contact lenses can improve vision, but be uncomfortable to wear for extended periods - sometimes beyond just a few hours a day. Further, they are believed to contribute and exacerbate corneal scarring, which may be a manifestation of the disease. Patients typically are informed upon diagnosis that they would likely require contact lenses eventually. Although most patients can continue to read and drive, some feel quality of life is adversely affected. Patients undergo eye examinations annually or more frequently to monitor progression. About 20% of patients will eventually need a corneal transplant.
Keratoconus has no known cure, and many people do not even know they have it because it begins as nearsightedness (myopia) and astigmatism. It is a progressive disorder that may advance rapidly or sometimes take years to develop. It can severely affect the way we see the world, including simple tasks such as driving, watching TV, or just reading a book. Some keratoconus patients have described their vision as being "blind with light".
Various types of surgery are available for the patient with keratoconus who has progressed beyond correction with rigid contact lenses. Penetrating keratoplasty is the most common. In this procedure, the keratoconic cornea is prepared by removing the central area of the cornea, and a full-thickness corneal button is sutured in its place. An alternative is lamellar keratoplasty, a partial corneal transplant.