Corneal Thickness, Curvature and Topographic Indices: Implications for Keratoconus Screening in a South African University Clinic Population

Abstract

Background: Keratoconus (KC) is a progressive corneal ectatic disorder characterised by thinning and irregular steepening, which may lead to visual impairment if not detected early. Most diagnostic thresholds are derived from non-African populations, limiting their relevance in local settings. Aim: To profile corneal thickness, curvature, eccentricity and topographic indices, and assess their implications for keratoconus screening in a South African university clinic population. Methods: A quantitative cross-sectional study was conducted using clinical data from patients attending a university optometry clinic. Mean central corneal thickness (CCT), radius of curvature ( r ), eccentricity ( e ) and KC related indices of 300 clinic patients were measured using Oculus Pentacam. Descriptive and inferential statistics were used to analyse the data. Results: Corneal parameters were generally within normal ranges. The mean CCT was 504.79 ± 33.12 μm. The mean r was 7.83 ± 0.28 mm, indicating relatively flatter corneas compared to some international populations. Mean e- value was 0.47 ± 0.13, suggesting prolate corneal profiles. Keratoconus related indices were largely within normal limits, although they appeared more conservative than corneal thickness in identifying suspected ectasia. Weak to moderate correlations were observed between variables. Conclusion: Corneal characteristics were within normal limits but showed subtle population specific variation. A multi-parameter approach integrating thickness, curvature and indices is recommended to improve KC screening and to strengthen region-specific diagnostic thresholds. Keywords: keratoconus, corneal thickness, corneal curvature, eccentricity, ectasia screening, topographic indices, South Africa