Purpose: To investigate hemodynamic changes after strabismus surgery using color Doppler imaging (CDI). Method: Group 1 patients (n = 13) underwent surgery on a single horizontal rectus muscle, and group 2 (n = 13) underwent surgery on both horizontal rectus muscles. Subjects with no systemic or ophthalmologic disorders were selected as controls (n = 16). In group 1 and group 2, CDI of the ophthalmic artery (OA), the central retinal artery (CRA), and the nasal and temporal posterior ciliary arteries (PCAs) was performed before surgical correction and on postoperative days 1 and 7. For each vessel, peak systolic (V-max), end diastolic (V-min), and mean (V-mean) blood flow velocities were measured, in addition to the resistivity index (RI) and pulsatility index (PI). Results, V-max in the OA on postoperative day 1 was higher in group 2 than in group 1 (P=.004). V-min in the OA on postoperative day 1 was significantly higher in group 2 than in the controls (P=.001) and group 1 (P=.001). For group 2, comparison of the OA preoperative findings to the findings on postoperative day 1 showed that V-min (P=.003) and V-mean (P=.02) increased significantly, and the RI (P=.01) and PI (P=.006) decreased significantly. These significant differences were not observed on day 7 (P>.05). Conclusion: Surgery on both horizontal rectus muscles in an eye causes hemodynamic changes in the OA in the early postoperative period.