Keratoconus and Contact Lenses

Keratoconus is a genetic, recessive condition that affects less then 1% of the population, is progressive and can have devastating affects on the vision. There are several types of the condition each demonstrating varying degrees of severity.

The mild variation of the condition will present with decreased vision that is most often treated with eye glasses. The vision is corrected to 20/20 and frequently no diagnosis is even made.

When the vision continues to get worse, additional testing must be done to determine the etiology of the changes. A corneal topography must be performed to make the ultimate differential diagnosis. The inferior nasal area of the cornea is steeper then the rest of the cornea and is the only possible diagnosis. When this occurs careful examinations must be performed in order to maximize the visual acuity. When acceptable vision is not achieved with eye glasses, then Gas Permeable contact lenses must be employed. These lenses mask the irregularities of the cornea and give the best visual results.

As the condition continues to progress the central cornea near the cone will get thinner and protrude anteriorly. Danger exists when the apex of the cone touches the posterior surface of the contact lens. This interface can result in scarring of the cornea and permanent decreased vision. Careful and frequent evaluations must be performed to continuously redesign the lens to vault over the cone. On occasion, if an acceptable fit can not be achieved then a “piggy back” method must be used. This involves fitting a soft contact lens under the gas permeable one. The soft lens acts as a cushion and protects the cornea while still maintaining good comfort and vision.

I recently had a patient whose corneas had progressed to the level that even the piggy back was not giving the patient enough comfort so I had to refit the worse eye with a custom made soft contact lens specifically designed for Keratoconus. This increased the comfort and prevented the eye from getting an apical scar from the lens. The best vision in that eye was not as good as possible, but in combination with the other eye which still had a gas permeable lens, the vision was adequate.

If the condition progresses to the level that no improvement can be achieved with lenses, then a corneal graft must be performed. That topic will be discussed in another article.

In short, if a patient has declining vision that appears to be irregular in nature, Keratoconus must be considered and special contact lenses employed.