Diagnostic value of the pachymetry parameters measured by RTVueOCT for keratoconus

Background: This study aimed to investigate the diagnostic value of pachymetry parameters measured by RTVueOCT for keratoconus. Methods: 74 patients with 118 eyes diagnosed with keratoconus were enrolled in keratoconus group and 60 patients with normal 120 eyes as health controls. Pachymetry parameters were measured. The major indicators were tested: 1) S-I value: difference between the mean superior and the mean inferior corneal thickness; 2) SNIT value: difference between the mean superonasal and the mean inferotemporal corneal thickness; 3) MIN: values of minimum corneal thickness; 4) Min-Med: difference between minimum and median corneal thickness; 5) Min-Max: difference between minimum and maximum corneal thickness; 6) the thinnest X-location; 7) the thinnest Y-location. The seven parameters were measured within 5 mm of optical center. Results: The thinnest corneal thickness in keratoconus group and control group was 423.5 ± 58.72 um and 539.15 ± 25.64 um respectively. There were significance differences of SN-IT, S-I, Min, Min-Med and Min-Max between keratoconus group and control group. AROC of IT-SN, I-S, Min, Min-Med and Min-Max were 0.869, 0.814, 0.991, 0.996 and 0.996 respectively. Cut-off values of SN-IT, S-I, Min, MinMedian and Min-Max in distinguishing control group and keratoconus group were -28.5 μm, -33.5 μm, 497.0 μm, -22.5 μm and -53.0 μm respectively; sensitivities were 0.839, 0.627, 0.946, 0.966 and 0.975; and specificities were 0.842, 0.917, 0.967, 1.000 and 0.958 respectively. Conclusions: The pachymetry parameters measured by RTVueOCT can be used in diagnosis of keratoconus effectively.