Keratoconus

Keratoconus is an uncommon condition in which the cornea (the clear front window of the eye) becomes thin and protrudes. Keratoconus literally means a cone-shaped cornea. This abnormal shape can cause serious distortion of vision.

What causes keratoconus?

Research indicates that keratoconus may be caused by an excess of enzymes that break down the proteins within the corneal surface, causing the cornea to thin and protrude.

The genetic inheritance of keratoconus has not clearly been determined. It appears that it may involve a number of different genes. Blood relatives of someone affected with keratoconus may have minor changes in their corneas that indicate that keratoconus probably varies both in the specific genetic cause, as well as in its expression within a family.

Vigorous eye rubbing may contribute to the disease process. People with keratoconus should avoid rubbing their eyes. This is sometimes very difficult because some allergies, which cause itchy, irritated eyes, are more commonly associated in patients with keratoconus.

What are the symptoms of keratoconus?

Blurring and distortion of vision are the earliest symptoms of keratoconus. Symptoms usually appear in the late teens or early twenties. The disease will often progress slowly for 10 to 20 years, then stop.

In the early stages, vision may be only slightly affected, causing glare, light sensitivity and irritation. Each eye may be affected differently. As the disease progresses and the cornea steepens and scars, vision may become distorted.

A sudden decrease in vision can occur if the cornea swells. The cornea swells when the elastic part of the cornea develops a tiny crack, created by the strain of the cornea's protruded cone-like shape. The swelling may persist for weeks or months as the crack heals and is gradually replaced by scar tissue.

How is keratoconus treated?

If eyeglasses cannot fully correct vision, rigid contact lenses can make a remarkable difference in the clarity of vision. Newer materials and designs enable many people with keratoconus to enjoy wearing contact lenses longer.

Other ocular conditions are often seen in association with keratoconus, such as atopic or allergic red eye (conjunctivitis). These conditions can be treated with the appropriate drops and cleansing routine to enable comfortable contact lens wear.

When contact lenses cannot improve your vision adequately, a corneal transplant may be necessary. Less than 5% of people with keratoconus will require corneal transplant surgery. Keratoconus is one of the most common reasons for corneal transplant, and one of the most successful.