Pentacam accuracy in discriminating keratoconus from normal corneas: A diagnostic evaluation study

Objectives:This study aims to determine the diagnostic ability of Pentacam indices for keratoconus and identifying the best index for differentiating diseased from normal cases.Method:In this study, 150 keratoconus patients and 150 refractive surgery candidates with a definitive diagnosis of normal healthy corneas were enrolled. Initially, the placido disk topography imaging was performed. The keratoconus and normal corneas were defined based on placido disk topographic data from Rabinowitz-McDonnell. After complete eye examinations for all participants, they underwent Pentacam imaging, and corneal surface topographic indices were extracted. Multiple logistic regression was used to determine the best indices for differentiating diseased from healthy corneas, and the receiver operating curve was calculated to determine the diagnostic capability of each index.Results:Among the studied indices, the keratoconus index (KI), index of vertical asymmetry (IVA), thinnest point (TP), and maximum keratometry (Kmax) were found capable of detecting keratoconus. Among these, IVA was the best index, with an area under curve (AUC) of 95.24. The best cutoff point for IVA was 0.20 m, and its sensitivity and specificity were 87.50 and 96.30, respectively. Comparison of the AUC of different indices showed that only TP and IVA significantly differed (P=0.002). The combination of KI, IVA, Kmax, and TP indices leads to correct detection in 78 of cases.Conclusion:Measuring corneal topographic indices using Pentacam can be helpful in the diagnosis of keratoconus. According to the results of this study, IVA is the best diagnostic index for keratoconus. However, it is recommended to use a combination of Pentacam indices for more accurate differentiation of keratoconus from normal cases. © 2018 Contact Lens Association of Ophthalmologists, Inc