Keratoconus and abnormal corneal topography

The most common condition identified through topography is keratoconus or its subtle precursor condition forme fruste keratoconus. This relatively uncommon condition involves increased corneal thinning and steepening. Proceeding with laser vision correction in this condition can result in further thinning and steepening of the central cornea, a condition called ectasia. It occurs in approximately one in 2000 cases of LASIK.

It is important to note that most cases of this condition occurred in an era when the criteria on corneal topography for diagnosing forme fruste keratoconus were less stringent. The Pentacam corneal topographer has the Belin Ambrosio Index, a very objective and accurate predictor or keratoconus and hence forme fruste keratoconus. This index uses a database of patients who have developed ectasia. Their corneal topography has been compared statistically with the many patients who have had an uneventful recovery and who did not develop ectasia. The Belin Ambrosio is a relatively objective predictor of a given patient developing ectasia. Most patients have normal corneal topography and their ectasia risk is low. Pentacam corneal topographers are used at all our clinics and are state-of-the-art technology.