Longitudinal analysis of corneal topography in suspected keratoconus

Aims: To examine the incidence of progression of suspected keratoconus to true keratoconus and compare quantitative descriptors of corneal topography between eyes with and without progression. Methods: 34 eyes with suspected keratoconus were retrospectively reviewed in 34 patients. Their age at the initial examination was 13 to 40 years (24.1 (7.5), mean (SD)), and the follow-up periods ranged from 3 to 10 years (6.0 (2.2) years). Suspected keratoconus was defined as the fellow eye of a clinically apparent keratoconus but that had no slit-lamp signs of keratoconus (Fleischer ring, Vogt striae and Munson sign) with a 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. Using a 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 suspected keratoconus (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. The cumulative incidence of progression by Kaplan-Meier analysis was 21.5% in 6 years. The asymmetry component and regular astigmatism by Fourier analysis at the initial examination were significantly larger in the progression group than in the non-progression group. Conclusion: In our retrospective study, approximately 20% of eyes with suspected keratoconus progressed to true keratoconus in 6 years, and these eyes had presented greater asymmetry and regular astigmatism at the initial examination.