Longitudinal analysis of corneal topography in suspected keratoconus

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.

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.

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.

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.