Characteritic of Keratoconu and Pellucid Marginal Degeneration in Mean Curvature Map

Purpoe To characterize keratoconu and pellucid marginal degeneration (PMD) on mean curvature map. Deign Obervational cae erie. Method A retropective analyi of clinical record of 19 keratoconu eye and eight PMD eye. Keratometric mean curvature map were computed from a placido-dik-baed corneal topography ytem. The peak location and amplitude of ditortion were quantified by fitting two-dimenional Gauian function. Computer imulation of keratoconic corneal topography were ued to help interpret the reult. Reult Keratoconu and PMD eye had a characteritic localized increae in convexity (cone) on mean curvature map. Computer imulation howed that the peak on the mean curvature map accurately repreented the peak of the cone-like ditortion. However, the peak location and appearance of the ame conic ditortion on axial and tangential map were greatly influenced by coexiting atigmatim. The Gauian function provided an excellent model of keratoconu on mean curvature map, with a mean cro-correlation of 0.80. According to Gauian fitting, the vertical cone peak location were −1.10 ± 0.43 mm (mean ± D) in keratoconu eye and −1.94 ± 0.53 mm in PMD eye (P < .01). The location of peak on axial and tangential map differed coniderably from thoe on mean curvature map. Advanced keratoconu tended to have higher cone (amplitude 13.31 ± 6.87 diopter) than early keratoconu (amplitude 10.65 ± 1.56 diopter). Concluion Gauian fitting of mean curvature map accurately quantifie the peak location and amplitude of the cone in keratoconu and PMD eye. Thi new topographic analyi might be ueful in the diagnoi and tracking of corneal ectatic dieae.