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Keratoconus

Often appearing in the teens or early twenties, keratoconus is a progressive disease in which the normally round cornea thins and begins to bulge into a cone-like shape. This cone shape deflects light as it enters the eye on its way to the light-sensitive retina, causing distorted vision. Keratoconus can occur in one or both eyes.


Keratoconus Symptoms and Signs

Keratoconus can be difficult to detect, because it usually develops so slowly. However, in some cases, it may proceed rapidly. Nearsightedness and astigmatism also may accompany this disease, creating additional problems with distorted and blurred vision. Glare and light sensitivity also may be noticed. Keratoconic patients often have prescription changes each time they visit their eyecare practitioner. It's not unusual to have a delayed diagnosis of keratoconus, if the practitioner is not familiar with the early-stage symptoms of the disease.

What Causes Keratoconus?

New research has demonstrated a relationship between malfunction of beneficial enzymes found within the eye's surface and an accompanying chemical imbalance that leads to toxic damage and thinning of eye tissue. Because keratoconus can be found in extended families, this improper functioning of beneficial enzymes appears to have genetic causes about 5% of the time. Eye damage from keratoconus also can be linked to factors such as overexposure to sunlight, improper fittings of contact lenses, excessive eye rubbing, and continual (chronic) eye irritation.

New research has demonstrated a relationship between malfunction of beneficial enzymes found within the eye's surface and an accompanying chemical imbalance that leads to toxic damage and thinning of eye tissue. Because keratoconus can be found in extended families, this improper functioning of beneficial enzymes appears to have genetic causes about 5% of the time. Eye damage from keratoconus also can be linked to factors such as overexposure to sunlight, improper fittings of contact lenses, excessive eye rubbing, and continual (chronic) eye irritation.

In the mildest form of keratoconus, eyeglasses or soft contact lenses may help. But as the disease progresses and the cornea thins and changes shape even more, glasses or soft contacts will no longer correct your vision.

Other keratoconus treatments include:

Rigid gas permeable contact lenses: If eyeglasses or soft contact lenses cannot control keratoconus, then rigid gas permeable contact lenses are an option to consider. The firmer material of a rigid contact lens vaults over the irregular cornea better than a soft contact lens to improve vision. But rigid contact lenses can be more uncomfortable to wear than a soft lens. Fitting contact lenses on a keratoconic cornea is delicate and time-consuming. You can expect frequent return visits to fine-tune the fit and the prescription. The process will begin again when the cornea thins and distorts even more, altering the contact lens fit and prescription needed for clear, comfortable vision.

Intacs: (Addition Technology, Des Plaines, Ill.) Intacs or corneal inserts received U.S. Food and Drug Administration approval for treating keratoconus in August 2004, although the first cases in the United States were performed for keratoconus in 1999. These plastic inserts are placed just under the eye's surface in the periphery of the cornea, which helps achieve a flatter cornea leading to clearer vision. Intacs may be needed when keratoconus patients no longer can obtain functional vision with contact lenses or eyeglasses.

Several studies have found that Intacs improved keratoconic participants' eyeglass-corrected vision by an average of two lines on a standard eye chart. The implants also have the advantage of being removable and exchangeable. The procedure takes only about 10 minutes. Intacs might delay but can't prevent a corneal transplant if keratoconus continues to progress. Potential risks of Intacs are infection, little or no improvement in vision, glare and halos, and foreign body sensation, so it is important to discuss the procedure in detail with a surgeon to make sure you are a good candidate.

C3-R: (Advanced Vision Education, Los Angeles) Another new procedure for treating keratoconus, known by the brand name of C3-R (corneal collagen cross-linking riboflavin), is a non-invasive method of strengthening corneal tissue to halt bulging of the eye's surface. Specifically formulated eye drops containing riboflavin (vitamin B2) are placed on the cornea, and then activated by a special light to strengthen connective tissue (collagen) within the eye. C3-R may be combined with Intacs to treat keratoconus.

Early results showing benefits of using this method have been promising. In one small German study reported in the May 2003 issue of American Journal of Ophthalmology, progression of keratoconus was stopped in all 23 eyes of 22 patients. Most patients also had some reversal of keratoconus and minor vision improvement. Researchers concluded that this simple method of treatment might have implications for greatly reducing the need for corneal transplants for keratoconus patients.

Corneal transplant: Some people with keratoconus can't tolerate a rigid contact lens, or they reach the point where contact lenses or other therapies no longer provide acceptable vision. The last remedy to be considered may be a cornea transplant, also called a penetrating keratoplasty. Even after a transplant, you most likely will need glasses or contact lenses for clear vision.

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