Anterior segment blood supply after horizontal rectus muscle surgery using optical coherence tomography angiography

OBJECTIVE: To evaluate the change in anterior segment blood supply after horizontal rectus muscle surgery using anterior segment optical coherence tomography angiography (AS-OCTA) and to explore the influencing factors. METHODS: This prospective, longitudinal study included patients undergoing horizontal rectus muscle surgery. AS-OCTA images of the iris and episcleral-limbal plexus (ELP) were captured preoperatively and at 1 day, 1 week, 1 month and 3 months. Vessel densities were calculated and compared among different groups. Risk factors were explored using stepwise multivariate linear regression. RESULTS: Sixty patients were enrolled and underwent surgery, 24 for lateral rectus muscle (LR), 11 for medial rectus muscle (MR), and 25 for unilateral medial and lateral rectus muscles (R&R). Vessel densities in the LR group recovered to the preoperative level at postoperative 1 week (ELP: P = 0.052; Iris: P = 0.065), whereas not until 1 month postoperatively in the MR (ELP: P = 0.084; Iris: P = 0.383) and R&R groups (ELP nasal side: P = 0.454; ELP temporal side: P = 0.929; Iris: P = 0.563). The MR and R&R groups experienced greater decreases in iris vessel density (MR: 1.44 ± 1.43 %, P = 0.021; R&R: 1.12 ± 1.42 %, P = 0.021) than the LR group (0.26 ± 0.62 %). Older age (P < 0.001), increased BMI (P = 0.014), and smoking history (P = 0.008) were strong indicators for poorer iris recovery at postoperative 1 month. CONCLUSION: Horizontal rectus muscle surgery induced decreased anterior segment blood supply, which averagely recovered within 1 month. Patients predicted at high risk including those of older age, increased BMI, or a smoking history, may benefit from regular monitoring with AS-OCTA.