Evaluation of Scheimpflug imaging parameters in subclinical keratoconus, keratoconus, and normal eyes

Purpose: To determine the efficacy of different Scheimpflug-imaging parameters in discriminating between subclinical keratoconus, keratoconus eyes, and normal eyes.

Setting: Department of Ophthalmology, Ankara University Faculty of Medicine, Ankara, Turkey.

Design: Comparative case series.

Methods: Pentacam Scheimpflug measurements were taken in eyes with mild to moderate keratoconus, subclinical keratoconus, or with myopic astigmatism (normal eyes). Several parameters provided by the software or derived from the elevation maps were evaluated and compared between the groups. The Mann-Whitney test, receiver-operating-characteristic (ROC) curves, and logistic regression analysis were used to compare the mean measurements and to evaluate the sensitivity and specificity of the parameters or constructed models.

Results: The corneal power and elevation measurements were statistically significantly higher and the cornea was significantly thinner in eyes with subclinical or clinical keratoconus than in normal eyes (P < .05). The ROC curve analysis showed high overall predictive accuracy of various elevation and thickness indices in discriminating ectatic corneas from normal corneas. Logistic regression analysis showed that the goodness of fit of a model using a combination of corneal power, thickness, and anterior elevation parameters was best in discriminating keratoconus eyes from normal eyes, whereas that of a model using a combination of corneal power, thickness, and posterior elevation was best in discriminating subclinical keratoconus eyes from normal eyes.

Conclusion: Combined analysis of anterior and posterior corneal power, elevation, and thickness data provided by the Scheimpflug device effectively discriminated between ectatic corneas and normal corneas.

Financial disclosure: No author has a financial or proprietary interest in any material or method mentioned.