Overview

Keratoconus (ker-uh-toe-KOH-nus) is an eye disease in which the clear, dome-shaped front of the eye, called the cornea, becomes thinner, steeper, and bulges outward into a cone shape.

A cone-shaped cornea causes blurred vision and can cause sensitivity to light and glare. Keratoconus usually affects both eyes. However, it can affect one eye more than the other. It generally begins to affect people between the late teens and 30s. The condition can develop slowly for 10 years or longer.

In the early stages of keratoconus, you may be able to correct vision problems with glasses or soft contact lenses. Later, you may need to be fitted with rigid, gas-permeable contact lenses or other types of lenses, such as scleral lenses. If your condition worsens, you may need a corneal transplant.

A procedure called corneal collagen cross-linking can help slow or stop keratoconus from progressing, possibly preventing the need for a future cornea transplant. This treatment can be offered in addition to the above options for vision correction.

Symptoms

Symptoms of keratoconus may change as the disease progresses. They include:

• Blurred or distorted vision.
• Increased sensitivity to bright light and glare, which can cause problems when driving at night.
• A need for frequent changes in eyeglass prescriptions.
• Sudden worsening or blurring of vision.

When to see a doctor

See your eye doctor if your vision worsens rapidly. This can be caused by an irregular curvature of the eye, called astigmatism. Your eye doctor may also look for signs of keratoconus during routine eye exams.

Reasons

No one knows what causes keratoconus, although genetic and environmental factors are thought to be involved. About 1 in 10 people with keratoconus also have a parent with the condition.

Risk factors

These factors can increase the risk of developing keratoconus:

• Having a family history of keratoconus.
• Rub the eyes vigorously.
• Having certain conditions, such as retinitis pigmentosa, Down syndrome, Ehlers-Danlos syndrome, Marfan syndrome, hay fever, and asthma.

Complications

In some situations, the cornea can swell rapidly and cause sudden vision loss and corneal scarring. This is caused by a condition where the inner lining of the cornea, called Descemet’s membrane, breaks down. This causes fluid to enter the cornea, a condition known as hydrops. The swelling usually goes away on its own, but a scar can form which affects vision.

Advanced keratoconus can also cause the cornea to scar, especially where the cone is most prominent. A scarred cornea causes worsening vision problems and may require a corneal transplant.