Evaluation of relationships among refractive and topographic parameters

Abstract

Purpose: To examine the relationships among several refractive and topographic parameters. Setting: Cullen Eye Institute Department of Ophthalmology, Baylor College of Medicine, Houston, Texas, USA. Methods: Using computerized videokeratography (EyeSys Corneal Analysis System™), 287 corneas of 150 patients were retrospectively analyzed. The Holladay Diagnostic Summary (HDS) refractive maps were used to evaluate relationships among variables of the HDS and refractive error. Results: Myopic spherical equivalent refraction (P = .0003) and more negative asphericity (Q-values) (P = .0119) were correlated with steeper corneas. The Q-values were less negative in eyes with moderate myopia (2.0 to 6.0 diopters [D]) than in those with hyperopia (1.0 D or greater). The Q-values below −0.3 were correlated with less favorable values for predicted corneal acuity and corneal uniformity index values. Mean corneal curvature measurements obtained by computerized videokeratography and standard keratometry showed a strong degree of correlation (P = .0001). Conclusion: As the degree of myopia and negative asphericity increased, the corneal radius of curvature decreased. Corneal Q-values less than −0.3 were associated with reduced optical performance of the cornea.