Abstract
BACKGROUND: To investigate the vessel area density (VAD) and morphological features of the iris in patients at different stages of myopic macular degeneration (MMD) using swept-source optical coherence tomography angiography (SS-OCTA). METHODS: In this retrospective case-control study, 106 eyes of 106 high myopia patients (axial length (AL) ≥26 mm) were included and classified into different MMD categories according to the International META-PM Classification. The VAD of iris, iris volume (IV), area of anterior iris surface (IS), area of posterior IS, and average iris thickness (IT) were evaluated using SS-OCTA. Associations among iris vasculature, iris morphology, and MMD categories were investigated. RESULTS: Full-range, inner-region, and intermediate-region VAD of the iris decreased significantly with increasing MMD severity (all P-trend <0.001), whereas outer-region VAD did not show a significant linear trend. The area of IS was larger in eyes with MMD 2 and MMD 4 compared to the other two groups (all P <0.05). The full-range and outer-region VAD of iris was negatively correlated with AL, while the inner-region VAD of iris was positively correlated with the area of anterior and posterior IS, especially in eyes with MMD 2 (all P <0.05). Multivariate linear regression revealed that greater full-range, inner-region and intermediate-region VAD were all significantly associated with milder MMD, whereas greater outer-region VAD was significantly associated with shorter AL. CONCLUSIONS: Iris blood flow, quantified by VAD, decreased with increasing MMD severity. Iris VAD may represent a promising candidate biomarker for non-invasive monitoring of MMD severity. Additionally, the association between VAD and AL or iris morphology varied across MMD categories.