Evaluation of keratometric, pachymetric, and elevation parameters of keratoconic corneas with pentacam

The purpose of this study was to evaluate the alteration of keratometric, pachymetric, and elevation parameters of keratoconic and normal corneas with the Pentacam Scheimpflug camera.

Pentacam measurements were performed on 41 eyes of 24 patients with keratoconus and 70 eyes of 41 normal subjects. In each eye, keratometric values, central and minimal pachymetry, and anterior and posterior elevation were evaluated. Receiver operating characteristic curves were used to compare the sensitivity and specificity of the different parameters. Predictors of keratometric, pachymetric, and elevation data were evaluated by logistic regression analysis. Confirmatory factor analysis was performed in the keratoconus group to quantify the validity of critical parameters for keratoconus.

All parameters were significantly different in the keratoconus group compared with the normal control group. Receiver operating characteristic curve analyses showed the best predictive accuracy for posterior and anterior elevation (area under the curve, 0.97 and 0.96) followed by minimal and central pachymetry (0.89 and 0.88). The optimal cutoff point for posterior elevation was 15.5 microm for the discrimination of keratoconus corneas from normal. Logistic regression analysis showed best fit to the data for the model completed with the height data of the Pentacam. Confirmatory factor analysis explained a 3-factor model satisfactorily showing minimal pachymetry (-0.99), anterior elevation (0.98), and keratometry (0.95) as the most representative clinical variables of the disease.

Posterior and anterior elevation, pachymetric, and keratometric parameters measured by the Pentacam camera can effectively discriminate keratoconus from normal corneas serving as a useful diagnostic tool for disease staging.