Metrics of anterior sclera in normal Chinese adults: Anterior segment imaging using the swept-source optical coherence tomography Running

Abstract

Abstract Background: To measure the corneoscleral limbus and anterior sclera parameters of normal Chinese adults by swept-source optical coherence tomography (OCT). Methods: In this cross-sectional study, a total of 56 Chinese subjects with ametropia were evaluated in the Eye Hospital of Wenzhou Medical University from September 2020 to December 2020, including 26 (46.4%) men, with an average age of 24.7±1.8 years old, and a spherical equivalent of -2.05±0.46 D. The optical coherence tomograph SS-1000 (CASIA, Tomey, Tokyo, Japan) was used to measure the sagittal height, corneoscleral junction angle (CSJ), corneal angle, and scleral angle. One-way analysis of variance and least significant difference test were used to compare the differences in the four segment parameters. Results: The mean sagittal heights of the right eyes at chord lengths of 10.0, 12.3, and 15.0 mm were 1756±72, 2658±110, and 3676±155 μm, respectively. The absolute values of the differences between horizontal and vertical meridians at chord lengths of 10.0, 12.3, and 15.0 mm were 54±40, 70±67, and 117±95 μm, respectively. The differences of CSJ and corneal angles at 12.3 mm chord and scleral angle at 15.0 mm chord in the four segments were statistically significant (F values were 32.01, 21.31, and 13.37, respectively, all P values < 0.001). The CSJ angles from low to high were 176.53±2.14° (nasal), 178.66±1.84° (inferior), 179.13±1.20° (temporal), and 179.31±1.68° (superior), and 87.5% of the nasal angles were less than 179°. The corneal angles at 12.3 mm chord from high to low were 40.31±2.80° (nasal), 39.46±2.41° (temporal), 37.20±2.26° (inferior), and 37.50±2.28° (superior). The scleral angles at 15.0 mm chord from high to low were 38.35±2.47° (temporal), 38.26±3.37° (superior), 35.37±3.10° (nasal), and 35.30±4.71° (inferior). Conclusion: The morphology of corneoscleral limbus and anterior sclera is asymmetrical in normal Chinese adults. The nasal side of the corneoscleral limbus has the largest angle, and the superior and temporal sides of the scleral angle are larger. From the corneoscleral limbus to the anterior sclera, the superior side becomes steep and the other segments become flat.