Sleep is important in maintaining the physiological function of the human body. Recently several studies have reported that preoperative sleep quality is associated with postoperative emergence delirium (ED) The ED is a common in pediatric patients undergoing general anesthesia with sevoflurane, but studies on the association of sleep quality have been rare. The investigators, therefore, aimed to investigate the relationship between postoperative delirium and pre and postoperative sleep quality in pediatric patients receiving strabismus surgery through this study

This study aimed on pediatric patients aged 4-12 years, undergoing elective strabismus surgery. Informed consent was obtained from both parents and children on the day of pre-anesthetic evaluation visit. The child and his or her parents were questioned on preoperative patient's sleep quality based on Pittsburg Sleep Quality Index (PSQI). Surgery was performed under the same anesthesia as usual. After the operation, extubation was performed and patient was moved to post anesthesia recovery room (PACU). During the stay in PACU, one investigator measured degree of ED by Watcha and PAED (Post anesthesia emergence delirium ) scale to minimize bias. One day after the surgery, the investigator mede a phone call to the parents of the patient to obtain information for postoperative PSQI.

Inclusion Criteria:

• Healthy children without any underlying diseases
• 4~12 years old
• Undergoing strabismus surgery

Exclusion Criteria:

• Any underlying diseases
• Disagree

Subject of this study is pediatric patients aged 4~12 years, undergoing elective strabismus surgery.