Anterior Segment Optical Coherence Tomography Indices and Their Value in Diagnosing Corneal Ectasia

Purpose: To determine the diagnostic value of the anterior segment optical coherence tomography (AS-OCT) indices in differentiating normal from ectatic corneas. Material and Methods: Two groups of patients—with corneal ectasia and normal controls were compared. Each group consists of 80 eyes of 43 age and sex-matched patients. All of them underwent corneal topography with OCULUS Keratograph 5M and corneal pachymetry with AS-OCT with RTVue-100. The indices generated by the AS-OCT pachymetric scans were analyzed. Results: There was a statistically significant difference for all the examined indices between the two groups with p values <0.001 and a confidence interval of 95%. The minimal corneal thickness (Min) was the best performing index according to the ROC analysis with an area under the curve of 0.976 and a combination of sensitivity and specificity of 0.925 and 0.911 respectively, and a “cut-off” value of 484 microns, followed by the indices of focal thinning—Min-Med and Min-Max with an area under the curve of 0.973 and 0.971 and sensitivity/specificity of 0.938/0.962 and 0.938/0.937 respectively. The rest of the examined parameters had an area under the curve in the range between 0.950 for the central corneal thickness and 0.814 for the outer superior segment. Conclusion: The anterior segment OCT indices showed excellent capability in differentiating ectatic from normal corneas.