Biometry-Based Technique for Determining the Anterior Scleral Thickness: Validation Using Optical Coherence Tomography Landmarks.

Abstract

Considering the potential role of anterior scleral thickness (AST) in myopia and the ubiquitous use of optical biometers, we applied and validated a biometry-based technique for estimating AST using optical coherence tomography (OCT) landmarks. The AST was determined across four meridians in 62 participants (aged 20-37years) with a swept-source OCT and a noncontact optical biometer at a mean ± SD distance of 3.13 ± 0.88mm from the limbus. The biometer's graticule was focused and aligned with the anterior scleral reflex, which led to the generation of four prominent A-scan peaks: P1 (anterior bulbar conjunctiva), P2 (anterior episclera), P3 (anterior margin of anterior sclera), and P4 (posterior margin of anterior sclera), which were analyzed and compared with the corresponding OCT landmarks to determine tissue thickness. The AST measurements between biometer and OCT correlated for all meridians (r ≥ 0.70, overall r = 0.82; coefficient of variation [CV], 9%-12%; P < 0.01). The mean difference ± SD between two instruments for overall AST measures was 3 ± 2.8 µm (range, -18 to +16µm; lower limits of agreement, -89 to +83 µm; P = 0.23) across all meridians. The mean ± SE AST with both instruments was found to be thickest at the inferior (562 ± 7µm and 578 ± 7µm) and thinnest at the superior (451 ± 7µm and 433 ± 6µm) meridian. The biometer demonstrated good intrasession (CV, 8.4%-9.6%) and intersession (CV, 7.9%-13.3%) repeatability for AST measurements across all meridians. The noncontact optical biometer, which is typically used to determine axial length, is capable of accurately estimating AST based on OCT landmarks. The high-resolution optical biometers can demonstrate wider application in the field of myopia research and practice to determine AST.