The cornea is the clear layer of tissue covering the front of the eye. In a healthy eye, the cornea is round. Keratoconus is an eye disease in which the cornea gradually thins and becomes cone-shaped over time.
The American Academy of Ophthalmology estimates that the condition affects one in every 2,000 Americans. It is believed that there is a genetic component, as well as environmental and hormonal factors, involved in the development of this thinning.
In the case of keratoconus, the thinning of the cornea falls under the category of diseases called dystrophies. Dystrophies are medical disorders in which the affected tissue or organ progressively wastes away. Keratoconus is the most common of the dystrophies affecting the cornea—the clear layer covering the front of the eye, according to the National Eye Institute.
Other parts of the body are not affected. The condition can occur in otherwise healthy people and usually appears in the teenage years or early 20s. Less frequently, keratoconus can be a complication resulting from other underlying eye diseases, such as Leber congenital amaurosis.
When the cornea tissue gradually wastes away, the thinning causes a bulge in the center that leads to the protrusion of the cornea into a cone shape, which can no longer focus incoming light properly. As a result, patients may suffer from double or blurred vision, myopia (nearsightedness), astigmatism, and sensitivity to light.
While keratoconus usually occurs in both eyes, it can progress differently in each eye. In the beginning stages, it is usually treated with glasses or soft contacts to correct vision. In later stages, special rigid contact lenses may be necessary to correct the vision distortion. This requires special fittings and more frequent check ups with an eye care professional.
While the disease typically begins in young people, vision usually stabilizes in 10 to 20 years. However, if the bulging becomes severe, there will be swelling of the cornea. In this case, tiny cracks appear and scar tissue accumulates in the cracks. The AOA notes that “if this sudden swelling does occur, your doctor can prescribe eyedrops for temporary relief, but there are no medicines that can prevent the disorder from progressing.”
For those with severe scarring, or for patients who cannot tolerate wearing contact lenses, a corneal transplant may be indicated. Even then, a patient may need to wear glasses to correct vision fully.
Routine eye care is necessary at all stages of keratoconus.