Longitudinal Changes in Corneal Curvature in Keratoconus

Abstract

Abstract: : Purpose: To identify factors that predict longitudinal increases in corneal curvature as measured by the First Definite Apical Clearance Lens (FDACL) and the flatter keratometric curvature measurement (Flat K) in keratoconus patients. Methods: The Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study is a long–term evaluation of the natural history of keratoconus involving 1209 subjects. This report uses eight years of follow–up from 1032 CLEK subjects excluding subjects who had penetrating keratoplasty in either eye at baseline and who provided enough data to compute the slope of the change over time in the FDACL or Flat K. Outcome measures included the aforementioned slopes and whether FDACL or Flat K increased by 3 or more diopters (D) in at least one eye. Results: Subjects at baseline were 38.9 + 10.8 years old, 44.3% female, and 69.3% Caucasian. The slope of the change in the FDACL (0.18 + 0.6 D/year) and Flat K (0.20 D + 0.8) over eight years translates into expected eight–year increases of 1.44 D in the FDACL and 1.60 D in Flat K. Increases of 3 or more diopters in either eye had an incidence of 24.8% for the FDACL and 24.1% for Flat K. Independent predictors of increased FDACL included younger age, poorer baseline high contrast (HC) manifest refraction visual acuity, and non–white race. Predictors of increased Flat K were younger age, poorer baseline HC manifest refraction visual acuity, and steeper baseline Flat K. Independent predictors for increases greater than 3.00 D for FDACL were younger age and poorer HC manifest refraction visual acuity. Predictors for Flat K with more than 3.00 D of change were younger age and poorer baseline HC manifest refraction visual acuity. Conclusions: CLEK subjects exhibited a slow but clear increase in corneal curvature during follow–up. Younger age and poorer HC manifest refraction visual acuity at baseline predicted the rate of change in corneal curvature.

Keywords: keratoconus • contact lens • cornea: clinical science