UNILATERAL KERATOCONUS - INCIDENCE AND QUANTITATIVE TOPOGRAPHIC ANALYSIS

Objective: This study was designed to determine the incidence of unila terality in a population of patients with clinical keratoconus and to compare quantitative descriptors of topography between affected cornea s from patients with unilateral keratoconus and corneas of patients wi th bilateral disease. Design: Retrospective clinical study with new ev aluation of some patients. Participants: One hundred sixty-four patien ts from the University of Texas Southwestern Medical Center and Wills Eye Hospital who were diagnosed to have moderate-to-advanced keratocon us on the basis of characteristic topographic patterns associated with corneal thinning. Intervention: Corneal topography was evaluated in b oth eyes of each patient. Main Outcome Measures: Quantitative descript ors of corneal topography were compared between 5 affected corneas of patients with unilateral keratoconus (combined cases from University o f Texas Southwestern, LSU Eye Center, and Wills Eye Hospital) and 15 c orneas of patients with moderate-to-advanced bilateral keratoconus (1 cornea from each patient). Indices selected for statistical analysis w ere the Keratoconus Predication Index (KPI), Surface Asymmetry Index ( SAI), and Surface Regularity Index (SRI). Results: Three (1.83%) of 16 4 patients with moderate-to-advanced keratoconus had no topographic ev idence of keratoconus in the opposite eye. There were no statistically significant differences in KPI, SRI, or SAI values between the affect ed corneas of patients with unilateral and bilateral keratoconus. Over a period of 4 years of observation, signs of keratoconus in the previ ously normal eye developed in a patient with unilateral keratoconus. C onclusions: The authors found no differences in the quantitative descr iptors of corneal topography between corneas with keratoconus from uni lateral and bilateral cases. The authors' results suggest that the inc idence of ''unilateral'' keratoconus is very low, Patients initially d iagnosed with unilateral keratoconus, if observed for a sufficient per iod, commonly had signs of keratoconus develop in the opposite eye. Th e possibility that all cases of unilateral keratoconus may eventually become bilateral cannot be excluded, Therefore, refractive surgical pr ocedures should not be performed on apparently normal corneas when ker atoconus is detected in the opposite eye.