Metrics of Anterior Sclera in Normal Chinese Adults: Anterior Segment Imaging Using the Swept-Source Optical Coherence Tomography

Purpose: To measure the corneoscleral limbus and anterior sclera parameters of normal Chinese adults by swept-source optical coherence tomography (OCT).Materials and 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. The OCT SS-1000 (CASIA, Tomey, Tokyo, Japan) was used to measure the sagittal height, corneoscleral junction (CSJ) angle, and scleral angle.Results: The chord was across the corneal center and the line connecting the center of the cornea and the center of the chord was perpendicular to the chord. The mean sagittal height at chord lengths of 10.0, 12.3, and 15.0 mm were 1,756 +/- 72, 2,658 +/- 110, and 3,676 +/- 155 mu m, respectively. The absolute values of the differences between horizontal and vertical meridians at three chord lengths were 54 +/- 40, 70 +/- 67, and 117 +/- 95 mu m, respectively. One-way analysis of variance showed that the differences of CSJ angles at 12.3-mm chord and scleral angles at 15.0-mm chord in the four segments were statistically significant ( F values were 32.01 and 13.37, respectively, both P <0.001). The CSJ angles from low to high were 176.53 +/- 2.14 degrees (nasal), 178.66 +/- 1.84 degrees (inferior), 179.13 +/- 1.20 degrees (temporal), and 179.31 +/- 1.68 degrees (superior), and 87.5% of the nasal angles were less than 179 degrees. The scleral angles from high to low were 38.35 +/- 2.47 degrees (temporal), 38.26 +/- 3.37 degrees (superior), 35.37 +/- 3.10 degrees (nasal), and 35.30 +/- 4.71 degrees (inferior).Conclusions: 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.