Comparative Evaluation of Elevation, Keratometric, Pachymetric and Wavefront Parameters in Normal Eyes, Subclinical Keratoconus and Keratoconus with a Dual Scheimpflug Analyzer

Purpose: To compare the corneal parameters in normal corneas, forme fruste keratoconus (FFKC) and keratoconus measured with a dual Scheimpflug analyzer. Materials and methods: A total of 372 eyes of 197 patients were prospectively enrolled in the study and divided into three groups: 148 eyes of 102 patients with keratoconus, 47 contralateral topographically normal eyes of clinically evident keratoconus in the fellow eye and 177 eyes of 95 refractive surgery candidates with normal corneas. All eyes were measured with a dual Scheimpflug analyzer and elevation, keratometric, pachymetric and wavefront data were analyzed. Mean and intergroup comparisons were performed for 43 parameters. Results: Eighty-eight percent of the parameters analyzed (38/43) were significantly different between normal and keratoconus whereas it was less than 40% (17/43) between normal and FFKC. The majority of the elevation parameters were significantly different between normal eyes and FFKC (11/14) whereas the I-S value and the Kmax were the only two parameters related to the anterior curvature that were significantly different between both groups. Corneal vertical coma was the only corneal aberrations significantly different between normal and FFKC (p < 0.07). Conclusion: The dual Scheimpflug analyzer provides useful parameters for differentiating normal corneas, FFKC and keratoconus.