Is the interocular choroidal structure symmetrical in healthy people? Results of symmetry studies with different partitioning methods.

Abstract Objective: To investigate the symmetry of the interocular choroidal structure in a healthy population by developing novel partitioning methods utilizing 120° ultra-wide field swept-source optical coherence tomography angiography (SS-OCTA). Methods: This cross-sectional observational study enrolled 135 healthy volunteers (270 eyes) for single 24 mm × 20 mm SS-OCTA imaging of the fundus across a 120° FOV (field of view), centered on the macula. Various partitioning methods were designed to compare the interocular symmetry of choroidal structure. Results: The interocular choroidal thickness among subjects exhibited symmetry in dichoptic, concentric circle, cruciform, and macular concentric circle + quadratic partitioning modalities. Otherwise, in the ETDRS partitioning, the mean choroidal thickness (MCT) of the right eye's upper macular epiretinal region (271.74±77.69 µm) was significantly greater than that in the left eye (263.94±75.37 µm), p = 0.019*. Furthermore, in the nine-partitioning method, the MCT of the left eye's temporal lateral region (212.44±48.41 µm) was higher than that in the right eye (208.58±46.53 µm), p= 0.048*. Conclusion: Both the observation range and partitioning methods may influence the results of interocular symmetry in choroidal structure. Utilizing contemporary population data, our study reveals that newly developed partitioning methods show symmetrical choroidal thickness across eyes.