Inclusion Criteria:  Patients received surgeries with high-risk OVR, including the strabismus surgery, the posterior scleral reinforcement, and the insertion of ocular implant.  Exclusion Criteria:  Those who have pre-existed vocal cord damage before surgery (such as hoarseness, electronic laryngoscopy shows fixed vocal cords or arytenoid cartilage dislocation). Those with a history of surgery on the both sides of the neck (eg, thyroidectomy, carotid endarterectomy). American Society of Anesthesiologist (ASA) Grade > 3 Patients with infection at the neck puncture site, or severe coagulation abnormalities before surgery, or a history of local anesthetic allergy, or who have a pacemaker.