Keratoconus

Overview

Keratoconus is a disease of the cornea whereby the cornea develops ectasia or thinning and steepening, leading to reduced visual acuity. It is a progressive condition, occasionally occurring in families, and usually becomes apparent during adolescence. One eye typically worsens first, and the condition is often asymmetrical, with little or delayed involvement of the second eye. The keratoconus patient will typically experience decreased vision, due to the development of astigmatism. The eye care professional can detect the corneal irregularity with the use of a Keratometer, an instrument to measure corneal curvature, or, more recently, computerized video keratography, or corneal topography, whereby a map of the corneal shape can be depicted. (Example) In more advanced cases, thinning and scarring of the cornea is detectible using the slit lamp.

Treatment

Early cases of keratoconus may be treated with spectacles. As the irregularity progresses, adequate visual acuity is not achievable with spectacles, and contact lenses may be required. In early stages, soft contact lenses may be adequate, but typically rigid gas permeable contact lenses (RGP’s) are required. Special "cone” RGP’s, with multiple base curves, may be required to fit the cornea, and provide a smooth optical surface for focusing. Advances in contact lens making and design have allowed for the majority of keratoconus patients to have non-surgical treatment for their condition. With the most advanced cases, when contact lenses are either no longer tolerable or sub-optimal visual acuity is achieved, surgery becomes necessary. Corneal transplantation, or penetrating keratoplasty (PK), is performed in about 10% of cases. The thinned central portion of the cornea is removed and replaced with a corneal button of normal curvature from a donor eye that has been collected and analyzed by one of the many Eye Banks in the United States. PK is 90% successful in keratoconus, and often leads to restored useful vision. Occasionally contact lenses are still required post-corneal transplantation. Other forms of surgery, such as lamellar keratoplasty, and use of refractive surgical techniques such as Intacs or the excimer laser may be used to partially improve the condition.