Abstract: Objective To investigate the interocular differences in retinal and choroidal morphology and vascularity in patients with anisometropic myopia, and to further explore the relationship with myopia. Design Cross-sectional study. Participants 110 young patients with myopic anisometropia. Methods Using OCTA, measurements were obtained for retinal and choroidal thickness, retinal vessel length density (RVLD), choroidal vessel volume (CVV), choroidal stroma volume (CSV), and choroidal vessel index (CVI). Mean vessel width and branch points were derived from OCTA retinal images using custom Python scripts based on OpenCV. The interocular differences of the retinal and choroidal thickness, RVLD, CVV, CSV, CVI, mean vessel width and branch points were compared. Main Outcome Measures Retinal and choroidal thickness, RVLD, CVV, CSV, CVI, mean vessel width and branch points. Results In most regions, the retinal and choroidal thicknesses, as well as CVV and CSV, were lower in the more myopic eye compared to the less myopic eye. These measurements were correlated with spherical equivalent (SE) and axial length (AL) (all P＜0.05). Logistic regression analysis indicated that mean vessel width may be a significant factor influencing the refractive differences between the eyes in individuals（β=-0.157, P=0.019）. Restricted cubic spline analysis revealed that in the parafoveal zone, the CVI increased with SE when SE was less than -2.112 D, and decreased when SE was greater (P for nonlinear＜0.05). Conclusion In young anisometropic individuals, higher degrees of myopia were associated with thinner retinal and choroidal thicknesses, as well as reduced CVV and CSV, significantly linked to AL and SE. The threshold of the CVI parafoveal was identified at -2.112 D. Variations in mean vessel width suggest potential contributions to individual refractive anisometropia. (Ophthalmol CHN, 2025, 34: 40-46)

Key words: anisometropia, retina, choroid, OCTA