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

• Horizontal strabismus surgery disturbs blood flow, mostly recovering in 1 month. • Lateral rectus disinsertion less affects blood flow than medial rectus or both. • Older age, higher BMI, and smoking increase risk of poor blood flow recovery. • AS-OCTA is advisable for high-risk populations following strabismus surgery. : 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. : 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. : 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 =0.647; ELP temporal side: P =0.892; Iris: P =0.563). The MR and R&R groups experienced greater decreases in iris vessel density (MR: 1.18±1.45%, P =0.028; R&R: 1.27±1.50%, P =0.001) than the LR group (0.23±0.61%). 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. : 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.