Using three-dimensional modelling of the anterior sclera to investigate the scleral profile in myopic eyes

Abstract

Purpose: This study used three-dimensional (3D) modelling to investigate scleral profiles in myopic eyes and compare them with emmetropic eyes.

Methods: In this prospective observational study, the eyes of 151 participants were analysed using the corneoscleral profile module (CSP) of the Pentacam HR. Non-rotationally symmetrical ellipsoids were fitted to the anterior scleral sagittal height. Three radii were analysed, namely the nasal-temporal (Rx), superior-inferior (Ry) and anterior-posterior (Rz) orientations. Additionally, the area index (AI) and aspherical parameters (Qxy, Qxz and Qyz) of the anterior sclera-fitted ellipsoid (ASFE) were quantified.

Results: The findings showed an increase in Rx (-0.349 mm/D), Ry (-0.373 mm/D), Rz (-1.232 mm/D) and AI (-36.165 mm² /D) with increasing myopia. From emmetropia to high myopia, the vertical and horizontal planes of the anterior sclera became increasingly prolate (emmetropia, Qxz: 0.02, Qyz: 0.01; low myopia, Qxz: -0.28, Qyz: -0.28; high myopia, Qxz: -0.41, Qyz: -0.43). There were no significant differences in the coronal plane across the three groups (H = 2.65, p = 0.27). The anterior scleral shape of high myopes in the horizontal and vertical planes was more prolate than that of emmetropes and low myopes (Qxz, high myopes vs. low myopes: p = 0.03, high myopes vs. emmetropes: p < 0.001; Qyz, high myopes vs. low myopes: p = 0.04, high myopes vs. emmetropes: p < 0.001).

Conclusions: As the degree of myopia increased, non-uniform anterior scleral enlargement was observed. These findings provide a better understanding of the anterior segment with varying degrees of myopia.

Keywords: Scheimpflug camera; anterior sclera; corneoscleral profile; eye shape; myopia.