Measurement of scleral curvature using anterior segment optical coherence tomography

Abstract

Purpose To work out a way to measuring radius of scleral curvature using anterior segment optical coherence tomography (OCT). Methods Twenty four volunteers were enrolled. With OCT, horizontal and vertical images centered on the visual axis and four images centered on the upper, lower, nasal, and temporal limbus were obtained. To evaluate tangential radius of curvature, we used each nasal and temporal OCT image and calculated the radius of a circle, which passes by three points of scleral surface at 1, 2 and 3 mm from the limbus. To evaluate axial radius of curvature, central horizontal, nasal and temporal OCT images were composed to a new one and the radius of a circle, the center of which is on the visual axis and passes by the point of scleral surface at 2 mm from the limbus, was calculated. The differences in radius of curvature were analyzed by the student t‐test and correlation between two axial radii of curvature calculated by two different reviewers was measured by Pearson correlation coefficient. Results The mean axial radius of nasal curvature (13.33 ± 1.12 mm) was significantly longer than that of temporal curvature (12.32 ± 0.77 mm). The mean tangential radius of nasal curvature (15.14 ± 2.63 mm) was also longer than that of temporal curvature (14.18 ± 2.24 mm). The axial radii of nasal (13.33 ± 1.12 mm) and temporal (12.32 ± 0.77 mm) curvature from one reviewer were very close to those (13.01 ± 1.16 mm and 12.33 ± 0.78 mm) from the other reviewer (Pearson correlation coefficients 0.942 and 0.841, p < 0.001 in both). Conclusion Anterior segment OCT is a useful tool in measuring the radius of scleral curvature. Measurement of axial radius of curvature is more accurate than that of tangential radius of curvature, and has a good reproducibility.