Keratoconus

Overview

Keratoconus (ker-ah-to-ko’-nus) means to have a ‘coned-shaped cornea’. It is a relatively common and non-inflammatory progressive disorder whereby the normally round cornea becomes thin and irregularly conically shaped. The abnormal shape of the cornea prevents the light from correctly focusing on the retina. Called irregular astigmatism it results in blurred vision and visual distortions.

Nearly 10 per cent of new cases of keratoconus show some level of genetic transmission from a family member. Its definitive cause is unknown although there are several theories that exist. Some eyecare practitioners believe that keratoconus relates to other conditions such as atopic diseases for example endocrine disorders or Down’s syndrome. Others believe that it results from frequent rubbing of the eye as a relatively high percentage of patients with the disease indicated a history of forcefully rubbing their eyes. The cornea usually begins to change shape during puberty or early twenties and gradually develops thereafter although there may be periods of no growth. It is rare that the cornea distorts rapidly and causes a sudden change in vision. Either one or both eyes are affected.

Symptoms

In its earliest stages keratoconus can be difficult to detect as nearsightedness sensitivity to light astigmatism and blurred eyesight can occur with the illness. As keratoconus progresses however the cornea becomes more distorted and symptoms more apparent. These include:

• Blurred vision
• Distorted images,especially at distances
• Seeing halos of light around objects,especially at night
• Sensitivity to glare or light
• Disproportionate watering of the eyes

Treatment

For mild forms of keratoconus your eyecare practitioner can prescribe eyeglasses or soft contact lenses to correct your vision. As the disorder progresses rigid gas permeable contact lenses become a better alternative as they mimic the smooth surface of a healthy cornea thus minimizing the effects of the irregular astigmatism. Keratoconus patients often must schedule regular appointments with their eyecare provider as contact lenses require constant and usually time consuming fittings to adjust to the distortions of the cornea. Carefully fitted lenses are necessary to ensure correct vision. Lenses that do not fit properly might be uncomfortable and can aggravate the disorder.

In 10 to 20 per cent of cases the cornea reaches a state where there is too much scarring or contact lenses can no longer provide adequate vision.

In these cases a cornea transplant or corneal grafting is necessary. In a transplant the surgeon removes the cone-shaped cornea and replaces it with a donated one. Even after the operation however patients might still require glasses or contact lenses for clear vision. A corneal grafting procedure involves the grafting of a layer of corneal surface cells from the patient’s own cornea onto the sloped part of the cornea to reduce the cone shape. The success rate of both procedures is approximately 90 per cent.