Keratoconus is an uncommon condition in which the cornea, the clear front window of the eye, becomes thin and protrudes. This abnormal shape can cause serious distortion of vision. Its progression is generally slow and can stop at any stage from mild to severe.
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. Hereditary influences suggest that approximately 13% of patients have other family members with keratoconus. Unless there is evidence of keratoconus in successive generations of the family, there is only about a 1 in 10 chance that the children will develop keratoconus.
Vigorous eye rubbing can 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.
The actual prevalence of Keratoconus is not known. While it is not one of the most common of eye diseases, it is by no means rare. It has been estimated to occur in 1 out of every 2,000 persons in the general population. The disease usually shows up in young people at puberty or in their late teen years, but has also been first diagnosed in individuals in their forties and fifties as well. It is found in all parts of the US, and the rest of the world, with no significant geographic, gender, ethnic, or social pattern.
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. This is called acute hydrops. 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.
In the early stages of keratoconus, eyeglasses may be all that is needed to correct the mild prescription induced by the condition. However, as the keratoconus progresses, the corneal surface becomes more irregular making the vision through eyeglasses less acceptable. If eyeglasses cannot fully correct vision, rigid contact lenses can make a remarkable difference in the clarity of vision. Contact lenses work by creating a new artificial, smooth surface to the front of the eye, thereby correcting the induced prescription. Newer materials and designs enable many people with keratoconus to enjoy wearing contact lenses longer. Approximately 90% of individuals with keratoconus successfully manage their condition with contact lenses.
When contact lenses cannot improve your vision adequately, a corneal transplant may be necessary. It is estimated that only 20% 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. Although this is a very successful procedure, it also carries some serious complications that can occur. Because of this, corneal transplants are usually considered only in those cases in which contact lenses cannot be worn or do not provide adequate vision. Dr. Velasco can discuss the risks, benefits, and alternatives to surgery in your particular case.
Other ocular conditions are often seen in association with keratoconus, such as eyelid inflammation (blepharitis) or atopic or allergic red eye (conjunctivitis). These conditions can be treated with the appropriate drops and cleansing routine to enable comfortable contact lens wear. Dr. Velasco can advise you on how to appropriately treat these conditions.