2.1. Subjects

This was a prospective cross-sectional study that enrolled normal subjects of East Asian descent originating from mainland China, based on self-declaration, during routine ophthalmological examinations in the Eye, Ear, Nose, and Throat Hospital of Fudan University, Shanghai, China, from September 2014 to November 2019.

Data from both eyes were collected, including best corrected visual acuity (BCVA), measured using a standard Snellen chart and converted to logarithm of the minimum angle of resolution (logMAR) for statistical analysis; refraction data, converted to spherical equivalents (SEs), which were calculated as the spherical dioptric power plus one-half the cylindrical dioptric power; intraocular pressure (IOP), measured using a noncontact tonometer (TX-20, Canon, Tokyo, Japan); as well as the physical examination information of slit-lamp biomicroscopy and OCT examination.

The inclusion criteria of this study were SEs difference, defined as a difference in SEs between the right and left eyes of the same subject within −2.5 to +2.5 dioptres [D]; SEs in both eyes within −4 to +3 D; BCVA ≥ 20/25 in both eyes; no history of refractive surgery; IOP of 12–21 mmHg; no clinical signs or history of intraocular disease; and no staphyloma or choroidal excavation on any OCT image.