AIM: To investigate the features of retinal peripheral defocus and its associated variables in unilateral myopia. METHODS: This cross-sectional study included consecutive anisometropic myopic patients who visited Center for Optometry and Visual Science from August 2023 to March 2025 in Guangxi Zhuang Autonomous Region. Eyes were classified based on spherical equivalent(SE)and uncorrected visual acuity(UCVA): myopic eyes(SE ≤-0.50 D, UCVA <0.2 LogMAR)and contralateral normal eyes(SE ≥-0.25, UCVA ≥0 LogMAR). Total relative defocus value(TRDV)across the visual field, RDV at 15°, 30°, and 45°(RDV-15, RDV-30, RDV-45), and quadrant-specific RDV(superior/RDV-S, inferior/RDV-I, temporal/RDV-T, nasal/RDV-N)were compared between groups.RESULTS: This study enrolled 81 anisometropic patients(81 myopic eyes, 81 contralateral normal eyes). The cohort comprised 42 males and 39 females, 47 patients aged 8-12 y and 34 patients aged 13-17 y(mean age: 11.8±2.4 y). Myopic eyes demonstrated significantly higher values in TRDV, RDV-30, RDV-45, RDV-I, RDV-S, RDV-N, and RDV-T versus contralateral normal eyes(all P<0.001). RDV-15 showed no significant difference between groups in either 8-12-year-olds or 13-17-year-olds(both P>0.05). Among 13-17-year-olds, RDV-S also exhibited no intergroup difference(P>0.05). All other parameters differed significantly across both age strata(all P<0.05). In myopic eyes, age positively correlated with TRDV(r=0.31, P=0.005), RDV-30(r=0.33, P=0.002), RDV-45(r=0.32, P=0.004), and RDV-N(r=0.37, P<0.001). In contralateral eyes, scotopic pupil diameter negatively correlated with TRDV(r=-0.25, P=0.03), RDV-45(r=-0.25, P=0.02), RDV-S(r=-0.29, P=0.008), and RDV-N(r=-0.27, P=0.014). And age positively correlated with RDV-N(r=0.30, P= 0.006), axial length positively correlated with RDV-T(r=0.30, P=0.006). CONCLUSION: The peripheral defocus of unilateral myopic eyes varies from that of their contralateral normal counterparts. The former presents hyperopic defocus, which augments with age, while the latter displays myopic defocus, which accentuates with the increase of the scotopic pupil size.