What is Keratonconus?
Keratoconus is a condition where the normal rounded shape of the cornea becomes distorted and a cone-like bulge develops. This distortion causes significant visual impairment through blurring and clouding of sight. The progression generally occurs gradually and can stop at various stages leaving mild to severe impairment. As keratoconus develops over time, the cornea bulges and thins, which can cause irregularity and scarring.
What Causes Keratoconus?
There are several scientific theories to this condition, although the cause is still uknown. One viewpoint is that keratoconus is genetic in origin and is a consequence of abnormal growth or a congenitial defect. Another view is that it is a degenerative condition. A third perspective offers the theory that keratoconus is secondary to a disease process. This speculation occurred due to children with Down's syndrome, who usually have both eyes affected. Another hypothesis suggests involvement of the endocrine system since there is credence in the disease appearing at the onset of puberty.
Who Gets Keratoconus?
Approximately 1 in every 2,000 persons in the general population will develop this condition. Keratoconus is not a common eye disease, but it is not rare either. The disease tends to appear at the onset of puberty or in the later teenage years. It is found in the United States, as well as throughout the world, without regard to any known significance in geographic, cultural or social pattern.
The first sign of keratoconus is a blurring and distortion in vision. In the early stages of the condition, frequent eyeglass prescriptions for changes in nearsightedness and astigmatism correction can improve vision. The continued thinning of the cornea progresses slowly for 5 to 10 years and generally tends to stop. On occasion, if progression is rapid and develops into the advanced stage, a patient can develop clouding of vision in one eye that clears over a period of a week or months. The clouding or "acute hydrops" is caused by a sudden infusion of fluid into the stretched cornea. In advanced cases, the central part of the corneal bulge can form superficial scarring impairing vision.
How is Keratoconus Treated?
In the early stages of keratoconus, mild myopia (nearsightedness) and astigmatism can be treated with eyeglasses to correct vision. As the condition progresses, causing additional thinning and bulging of the cornea, contact lenses are a better method for managing distored vision formed by more pronounced astigmatism. In severe cases, a corneal transplant may be necessary.
To address the distortion created by keratoconus, several designs of contact lenses have been used in treatment. The most common form of contact lenses used for this condition are specific, custom-made rigid gas permeable (RGP) lenses.
RGP lenses are ideal due to a number of reasons:
- They can be customized to the unique shape of the eye, correcting almost all of the myopia and astigmatism associated with keratoconus.
- They provide oxygen to the cornea through the permeable surface.
- RGP lenses are easy to insert, remove and clean.
Other forms of contact lens treatment are also available. These include custom-made soft contact lenses, piggyback lenses using a RGP lens worn over a soft lens and large scleral lenses.
Frequent check-ups and lens changes due to the subtle and unpredictable changes caused by keratoconus to the cornea are necessary to correct vision distortion.