Abstract:   Objective  To investigate the clinical value of optical coherence tomography angiography (OCTA) combined with spectral-domain OCT (SD-OCT) in the quantitative assessment of macular microcirculation and choroidal structural changes in patients with high myopia, and to clarify the advantages of their synergistic evaluation and the correlations between various parameters and myopic maculopathy. Design Prospective case-control study. Participants A total of 50 patients (50 eyes) with high myopia (spherical equivalent ≤-6.00 D, axial length ≥26.5 mm) who visited the 969th Hospital of the Joint Logistics Support Force of the Chinese People's Liberation Army from January 2023 to December 2024 were included. Forty age- and sex-matched healthy individuals (40 eyes, refractive error ±0.50 D, axial length 22.0~24.5 mm) served as normal controls. The high myopia group was further divided into refractive subgroups (30 cases in the -6.00 D to -9.00 D group, and 20 cases in the <-9.00 D group) and lesion subtype subgroups [35 cases of simple high myopia, and 15 cases of myopic maculopathy, which included a choroidal neovascularization (CNV) subgroup of 7 cases]. Methods  All participants underwent OCTA (5 mm×5 mm scan) to detect superficial and deep retinal vessel density, choriocapillaris density, foveal avascular zone (FAZ) characteristics, and hemodynamic parameters. SD-OCT was performed to measure the subfoveal choroidal thickness (SFCT), choroidal layer parameters, and choroidal non-perfusion spot density. Independent sample t-tests and Chi-square tests were used to compare differences between groups. Spearman rank correlation was utilized to analyze the correlation among parameters, and partial correlation analysis was applied to evaluate the association between visual function and microcirculation parameters after controlling for refractive error. Main Outcome Measures  Microcirculation parameters (based on OCTA): superficial/deep retinal vessel density, choriocapillaris density, choroidal non-perfusion spot density, FAZ area, and morphological abnormality rate; Choroidal structural parameter (based on SD-OCT): SFCT; Clinical correlation indicators: best-corrected visual acuity (BCVA, LogMAR), macular ischemia index, and CNV detection rate. Results The superficial/deep retinal vessel density and choriocapillaris density in the high myopia group were significantly lower than those in the control group (all P<0.001), while the FAZ area, morphological abnormality rate, and choroidal non-perfusion spot density were significantly higher than those in the control group (all P<0.001). The SFCT significantly thinned with the progression of myopia severity [(215.34±32.15)μm in the -6.00 D to -9.00 D group vs. (168.76±28.45)μm in the <-9.00 D group, P<0.001)], and was significantly positively correlated with choriocapillaris density (r=0.412, P=0.005) and negatively correlated with BCVA (LogMAR) (r=-0.456, P=0.002). Compared with high myopia patients without CNV, the CNV subgroup exhibited lower deep retinal vessel density (19.87%±2.89% vs. 27.02%±2.65%, P<0.001), higher macular ischemia index (32.15%±5.12% vs. 18.67%±3.56%, P<0.001), greater choroidal non-perfusion spot density (0.92±0.31 spots/mm2 vs. 0.45±0.18 spots/mm2, P<0.001), and thinner SFCT (156.34±25.78 μm vs. 208.67±30.25 μm, P<0.001). The deep vessel density in the myopic maculopathy group was significantly lower than that in the simple high myopia group (22.15%±3.12% vs. 27.89%±2.34%, P<0.001), with a CNV detection rate reaching 46.67%. Conclusions  OCTA can non-invasively quantify the retinochoroidal vessel density, hemodynamics, and non-perfusion characteristics of the macular region in high myopia, whereas SFCT can accurately reflect the atrophic changes of choroidal anatomy. Their synergistic evaluation achieves a dual quantification of macular microvascular "structure-function," revealing the multi-level microcirculatory damage in high myopia more comprehensively than a single modality. The CNV subgroup presents with more prominent macular microcirculation impairments, suggesting that severe microcirculatory damage may be an essential pathological basis for CNV development. The combination of OCTA and SFCT provides comprehensive imaging evidence for the early screening, subtype differentiation, and severity assessment of myopic maculopathy.

Key words: High myopia, Macular area, Microcirculation, Subfoveal choroidal thickness