Comparison of and correlation between anterior and posterior corneal elevation maps in normal eyes and keratoconus-suspect eyes.

PURPOSE To compare the anterior and posterior corneal elevation maps between keratoconus-suspect eyes and normal eyes. SETTING Rothschild Foundation, AP-HP, University Paris VII, Hôpital Bichat Claude Bernard, Paris, France. METHODS The anterior and posterior corneal surface elevations were analyzed and compared in 60 normal myopic patients and 48 keratoconus-suspect patients. The anterior and posterior best-fit sphere radii, central and thinnest corneal pachymetries, anterior and posterior aconic shape parameters (aconic radius, aconic asphericity, aconic toricity), and anterior and posterior elevation in the 1.0 mm radius zone were analyzed. The correlations between elevation and aconic shape parameters between the anterior and posterior surfaces were compared. RESULTS The mean central and thinnest pachymetry values were significantly lower in keratoconus-suspect eyes (P<.0001). Compared with normal eyes, keratoconus-suspect eyes had significantly increased anterior toricity (P = .0002) and posterior toricity (P<.0001), more negative asphericity (P = .042), and higher posterior elevation (P<.0001). The correlation between aconic toricity and the anterior and posterior corneal surfaces was better in keratoconus-suspect eyes than in normal eyes. Aconic asphericity and apical curvature were less correlated in keratoconus-suspect eyes than in normal eyes. CONCLUSIONS The posterior corneal elevation and the corneal thickness values were different in keratoconus-suspect eyes. The correlation between the anterior and posterior corneal aconic shapes was between keratoconus-suspect eyes and normal eyes.