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Keratoconus is an eye disease that affects the structure of the cornea. The cornea is the clear tissue that covers the front of the eye.
With this condition, the shape of the cornea slowly changes shape from round to a cone shape. The eye bulges out. This causes vision problems.
The cause is unknown. It is likely that the tendency to develop keratoconus is present from birth. The condition may be due to a defect in collagen. This is the tissue that provides the shape and strength to the cornea.
Allergy and eye rubbing may speed up the damage.
There is a link between keratoconus and Down syndrome.
The earliest symptom is a slight blurring of vision that cannot be corrected with glasses. (Vision can most often be corrected to 20/20 with rigid, gas-permeable contact lenses.) Over time, you may have eye halos, glare, or other night vision problems.
Most people who develop keratoconus have a history of being nearsighted. The nearsightedness tends to become worse over time. As the problem gets worse, astigmatism develops.
Keratoconus is often discovered during the teenage years. It may also develop in older people.
Exams and Tests
The most accurate test for this problem is called corneal topography, which creates a map of the curve of the cornea.
A slit-lamp exam of the cornea can diagnose the disease in the later stages.
A test called pachymetry can be used to measure the thickness of the cornea.
Contact lenses are the main treatment for most patients with keratoconus. For people with the condition, wearing sunglasses outdoors after being diagnosed may help slow or prevent the progress of the disease. For many years, the only surgical treatment has been corneal transplantation.
The following newer technologies may delay or prevent the need for corneal transplantation:
- High-frequency radio energy (conductive keratoplasty) changes the shape of the cornea so contact lenses work better.
- Corneal implants (intracorneal ring segments) change the shape of the cornea so contact lenses work better
- Corneal cross-linking is an experimental treatment that causes the cornea to become hard. This stops the condition from getting worse. The cornea can then be reshaped with laser vision correction.
In most cases vision can be corrected with rigid gas-permeable contact lenses.
If corneal transplantation is needed, results are very often good. However, the recovery period can be long. Many people still need contact lenses after the surgery.
There is a risk of rejection after a cornea transplant, but the risk is much lower than with other organ transplants.
You should not have laser vision correction (such as LASIK) if you have any degree of keratoconus. Corneal topography is done beforehand to rule out people with this condition.
In rare cases, other laser vision correction procedures such as PRK may be safe for people with mild keratoconus.
When to Contact a Medical Professional
Young people whose vision cannot be corrected to 20/20 with glasses should be checked by an eye doctor familiar with keratoconus. Parents with keratoconus should consider having their children screened for the disease starting at age 10.
There is no way to prevent this condition. Some doctors believe that people should take steps to control allergies and avoid rubbing their eyes.
Dahl BJ, Spotts E, Truong JQ. Corneal collagen cross-linking: an introduction and literature review. Optometry. 2012 Jan;83(1):33-42.
Jain A, Paulus YM, Cockerham GC, Kenyon KR. Keratoconus and other noninflammatory corneal thinning disorders. In: Tasman W, Jaeger EA, eds. Duane's Ophthalmology. 2013 ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2013:vol 4, chap 16C.
Sugar J, Batta P. Keratoconus and other ectasias. In: Yanoff M, Duker JS, eds. Ophthalmology. 4th ed. St. Louis, MO: Elsevier Mosby; 2013:chap 4.18.
Reviewed By: Franklin W. Lusby, MD, ophthalmologist, Lusby Vision Institute, La Jolla, CA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.