Purpose This study aimed to evaluate and compare the discriminating ability of corneal elevation maps generated using a swept-source optical coherence tomography (SS-OCT) (SS-OCT ANTERION, Heidelberg Engineering, Heidelberg, Germany), which was estimated with different reference surfaces, to distinguish normal corneas from those with keratoconus and keratoconus suspect. Methods A total of 126 eyes of patients, which comprised 43, 37, and 46 keratoconus, keratoconus suspects, and normal controls, respectively, were included in this study. The anterior and posterior elevations at the thinnest point under the best-fit sphere (BFS) and toric-ellipsoid (BFT), respectively, and other corneal parameters were measured using the SS-OCT. In addition, the receiver operating characteristic (ROC) curve analysis and cut-off value were calculated to evaluate the diagnostic ability of the corneal elevation values in differentiating keratoconus and keratoconus suspects from normal eyes. Results The mean total keratometric and corneal elevation values were significantly higher in the keratoconus group than in the other groups. Pachymetric parameters exhibited the lowest values for keratoconus. In addition, ROC curve analyses showed a high accuracy of the thinnest point anterior and posterior BFT for both keratoconus and keratoconus suspects and normal controls (area under the ROC were 0.969 and 0.961, respectively). Furthermore, the optimal cut-off point of the posterior elevation at the thinnest point under BFT was 16.44 μm (sensitivity and specificity of 86% and 98%, respectively) for differentiating keratoconus from normal and keratoconus suspect eyes. Conclusions The elevation map using the BFS and BFT references measured with the anterior segment SS-OCT is considered an effective indicator for keratoconus diagnosis. Therefore, the anterior segment SS-OCT can effectively differentiate keratoconus from suspected keratoconus and normal corneas by measuring parameters such as posterior and anterior elevations, pachymetry, and keratometry.

Purpose To measure angle-to-angle (ATA) and spur-to-spur (STS) distances along six meridians using swept-source optical coherence tomography (SS-OCT) and compare with horizontal white-to-white (WTW) distance in different refractive error. Methods Overall, 126 eyes were assessed with the Anterion SS-OCT (Heidelberg Engineering, Heidelberg, Germany). ATA and STS distances were obtained using SS-OCT at 0, 30, 60, 90, 120, and 150 degrees. WTW was measured at 0 degree with built-in infrared camera. One way ANOVA test, pearson correlation coefficient, and stepwise multivariate regression analysis were used to compare ATA and STS distances with age, anterior chamber depth (ACD), axial length (AL), and simulated keratometric values (Sim K) in different refractive error groups. Results The mean MRSE refraction was +0.05 ± 0.23 D in the emmetropic group (41 eyes), -3.42 ± 3.04 D in the myopic group (44 eyes), and +1.33 ± 0.64 D in the hyperopic group (31 eyes). There was no statistical difference in the WTW of the emmetropic (11.62 ± 0.44 mm), myopic (11.79 ± 0.46 mm), and hyperopic groups (11.80 ± 0.49 mm) using one-way ANOVA (p = 0.007). ATA and STS were vertically oval in all groups. The correlation between ATA, STS and age, ACD, AL, and K values showed different significance for each meridian according to the refractive error. ATA increased as the horizontal WTW, ACD, and AL increased and Sim K decreased. STS shows relatively smaller explanatory power than ATA in the stepwise multivariate regression analysis. Conclusions This study is the first to analyze the relationship between ATA and STS compared to WTW by different refractive error. The difference between the horizontally oval WTW and vertically oval anterior chamber can be large, especially in myopia. ATA showed a greater positive correlation than STS with AL and ACD.