Abstract： Objective:To observe and analyze the macular microvascular system changes in unilateral pediatric uveitis (PU) and healthy contralateral eyes.Methods:A cross-sectional case-control study. From January 2019 to July 2021, 21 eyes of 21 patients with PU diagnosed in one eye (PU group), 21 unaffected contralateral eyes (contralateral eye group), and 21 age-matched volunteers with 21 eyes (NC group) during the same period were examined in Peking Union Medical College Hospital. Optical coherence tomography angiography was used to scan the 6 mm × 6 mm fundus macular area in the three groups of selected eyes to measure the vessel density of the superficial capillary plexus (SCP) and deep capillary plexus (DCP) of the retina, the area of the avascular zone (FAZ) in the fovea of the macula, the choroidal thickness under the fovea (SFCT), and the retinal thickness in the fovea of the macula (CRT). The device comes with a software choriocapillary flow measurement tool, which can obtain the macula's choriocapillary density (CCD) with the fovea as the center and the diameter of the annular area of 1.0 mm, 1.5 mm, and 3.0 mm, respectively. They were recorded as CCD-1.0, CCD-1.5, and CCD-3.0. The measurement data of multiple groups were compared by analysis of variance; if the variance of the three groups of data was not uniform, the Kruskal-Wallis test was used. Multiple linear regression analysis was used to evaluate the potentially related factors of CCD.Results:Compared with the contralateral eye group and the NC group, the vessel density of SCP ( H=-13.857,-25.500; P=0.043, P<0.001), DCP ( H=-15.333, -31.595; P=0.007, P<0.001) and CCD-1.0 ( H=-14.000,-16.214; P=0.040, 0.012) of the clinically quiescent PU group were significantly decreased. CRT and FAZ were not statistically different between PU and NC groups ( F=0.955; P=1.000, 0.661). Compared with the NC group, the mean vessel density of SCP and DCP in the contralateral eye group decreased, and the difference in DCP vessel density was statistically significant ( H=-16.262, P=0.004). There was no statistically significant difference between the CCD of two groups ( P=1.000). The SFCT of the PU group was significantly thicker than that of the NC group ( F=5.552, P=0.004), however, difference was not statistically significant from the fellow eye group ( F=5.552, P=0.270). The results of multiple linear regression analysis revealed that the CCD-1.0, CCD-1.5, and CCD-3.0 showed a linear correlation with the area of FAZ ( β=-0.494, -0.527, -0.566; P=0.015, 0.009, 0.010) and CRT ( β=-0.322, -0.466, -0.342; P=0.026, 0.002, 0.028). CCD-1.0 and CCD-1.5 showed a linear correlation with the vessel density of DCP ( β=0.277, 0.275; P=0.047, 0.045). Conclusion:Both retinal and choroidal microvasculature are abnormal in resting eyes with PU, and macular circulation disorders may be present in the unaffected fellow eye.