Evaluation of Corneal Thickness and Volume Parameters of Subclinical Keratoconus Using a Pentacam Scheimflug System

Purpose: To evaluate the efficacy of corneal thickness and volume parameters measured with the Pentacam Scheimflug system in discriminating subclinical keratoconus corneas and normal corneas.Methods: This study included 19 patients (19 eyes) with subclinical keratoconus and 29 patients (29 eyes) with myopic astigmatism as the control group. Corneas were evaluated using a Pentacam Scheimflug system (2002 model, Oculus, Berkshire, UK). We evaluated corneal thickness and volume parameters, including central corneal thickness (CCT), minimum corneal thickness (MCT), depressed corneal thickness (DCT), maximum progression index (MaxPI), average progression index (AvPI), minimum progression index (MinPI), and corneal volume values for the 3.0 mm (CV3), 5.0 mm (CV5), and 7.0 mm (CV7) central circles. Receiver operating characteristic (ROC) curves were used to compare the sensitivity and the specificity of the parameters. Partial least squares (PLS) analysis was used to construct models with corneal thickness and volume parameters for early diagnosis.Results: There were significant differences in all parameters (p < 0.001), except CV3 and CV5, between subclinical keratoconus and normal corneas. The diagnostic accuracy for all parameters was high, with an area-under-the-curve (AUC) of approximately 1. The optimal cutoff values for DCT, MinPI, AvPI, and MaxPI were 5.5, 0.95, 1.05, and 1.45 for subclinical keratoconus, respectively. The PLS model for subclinical keratoconus fit well to the CCT, MCT, MaxPI, AvPI, MinPI, CV3, and CV7 data.Conclusion: Thickness and volume parameters measured by the Pentacam Scheimflug system effectively discriminate subclinical keratoconus corneas from normal corneas.