*September 2009

In a longitudinal study, researchers at the Cornea-Genetic Eye Institute, Cedars-Sinai Medical Center in Los Angeles, California studied clinical signs and topography (videokeratography) maps of eyes in four groups of patients to determine whether there would be a useful correlation between the maps and clinical signs of keratoconus that might be used to detect subclinical keratoconus.

Classification scheme based on corneal topography and clinical signs to detect subclinical keratoconus

Drs. Li, Yang and Rabinowitz conducted a longitudinal study at the Cornea-Genetic Eye Institute, Cedars-Sinai Medical Center in Los Angeles, California to determine whether there would be a useful correlation between corneal topography (videokeratography) and clinical signs of keratoconus that might be used to detect subclinical keratoconus.

Based on clinical signs and videokeratography maps of eyes in four groups of patients, eyes were categorized as keratoconus, early keratoconus, keratoconus suspect or normal. Their videokeratography maps were examined when they entered the study (at baseline) and followed for 1 to 8 years.

Using known indices (mathematical algorithms) used to identify the features of keratoconus, the differences in quantitative videokeratography indices and the progression rate were evaluated. The quantitative indices studied were:

• central keratometry (K)
• inferior–superior (I–S) value
• keratoconus percentage index (KISA).

A mathematical relationship analysis was used to estimate the classification rate using these indices.

The results of the study found that there were significant differences at baseline between the normal, keratoconus-suspect, and early keratoconus groups in all indices. Over a median follow-up of 4 years, approximately 28% in the keratoconus-suspect group progressed to early keratoconus or keratoconus and 75% in the early keratoconus group progressed to keratoconus. Using all 3 indices and age, 86.9% in the normal group, 75.3% in the early keratoconus group, and 44.6% in the keratoconus-suspect group could be classified correctly using this classification scheme, yielding a total classification rate of 68.9%.

The cross-sectional and longitudinal data showed significant differences between groups in the 3 indices. Use of this classification scheme might form a basis for detecting subclinical keratoconus

Publication:

Keratoconus: Classification scheme based on videokeratography and clinical signs

Xiaohui Li, MD, MS, Huiying Yang, MD, PhD, Yaron S. Rabinowitz, MD

Journal of Cataract and Refractive Surgery

Volume 35, Issue 9, Pages 1597-1603 (September 2009)