Keratoconus is a deterioration of the structure of the cornea with gradual bulging from the normal round shape to a cone shape.
Causes, incidence, and risk factors: The cause is unknown. Keratoconus is more common in contact lens wearers and people with nearsighted eyes. Some researchers believe that allergy may play a role.
Symptoms: This condition causes decreased visual acuity . The earliest symptom is subtle blurring of vision that cannot be corrected with glasses. (Vision can generally be corrected to 20/20 with gas-permeable contact lenses.)
Signs and tests: Keratoconus is frequently discovered during adolescence. It can usually be diagnosed with slit-lamp examination of the cornea. Early cases may require a test called corneal topography, which creates a map of the curvature of the cornea.
When keratoconus is advanced, the cornea may be thinner in areas. This can be measured with a painless test called pachymetry.
Treatment: Contact lenses are the primary treatment and are satisfactory treatment for most patients with keratoconus. Severe cases may require corneal transplantation .
Newer technologies may use high frequency radio energy. This energy shrinks the edges of the cornea, which pulls the central area back to a more normal shape. It can help delay or avoid the need for a corneal transplantation.
Expectations (prognosis): In most cases vision can be corrected with gas-permeable contact lenses. Where corneal transplantation is needed, results are usually good after a long recovery period.
Complications: Patients with keratoconus should not have laser vision correction. Corneal topography is usually done before laser vision correction to rule out people with this condition.
Calling your health care provider: Young persons whose vision cannot be corrected to 20/20 with glasses should be evaluated by an eye doctor experienced with keratoconus.
Prevention: There are no preventive measures. Some specialists believe that patients with keratoconus should have aggressive treatment of ocular allergy and should be instructed not to rub their eyes.
References: Kymionis GD, Siganos CS, Tsiklis NS, et al. Long-term follow-up of Intacs in keratoconus. Am J Ophthalmol. Feb 2007;143(2):236-244.
Fay A. Diseases of the visual system. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 449
