Aims: To examine the incidence of progression of keratoconus suspect to true keratoconus and compare quantitative descriptors of corneal topography between eyes with and without progression.
Methods: We retrospectively reviewed 34 eyes with suspect keratoconus in 34 patients. Their age at the initial examination was from 13 to 40 years (24.1 ± 7.5, mean ± standard deviation), and the follow-up periods ranged from 3 to 10 years (6.0 ± 2.2 years). Keratoconus suspect was defined as the fellow eye of a clinically apparent keratoconus but that had no slit-lamp signs of keratoconus (Fleischer's ring, Vogt's striae, and Munson's sign) with best spectacle-corrected visual acuity of 20/20 or better. Eyes were monitored for the progression of apparent slit-lamp findings of keratoconus during the follow-up period. By using Fourier analysis of the corneal topography data, regular astigmatism, asymmetry component, and higher order irregularity component were calculated in the central 3-mm zone. Quantitative descriptors of corneal topography were compared between eyes which progressed to true keratoconus and those which did not.
Results: Five eyes (14.7%) progressed to apparent keratoconus from keratoconus suspect (progression group), and 29 eyes did not (non-progression group). On average, it took 5.2 years for the eyes to develop apparent slit-lamp findings of keratoconus. Cumulative incidence of progression by Kaplan-Meier analysis was 21.5% in 6 years. Asymmetry component and regular astigmatism by Fourier analysis at the initial examination was significantly larger in the progression group than in the non-progression group.
Conclusion: In our retrospective study, approximately 20% of eyes with suspect keratoconus progressed to true keratoconus in 6 years, and these eyes had presented greater asymmetry and regular astigmatism at the initial examination.