This study is a single-center, prospective, randomized, controlled trial. To investigate if preoperative using of eye patch will decrease emergence agitation, and to provide a better method of decreasing emergence agitation to pediatric ophthalmic anesthesiologists.

This study is a single-center, prospective, randomized, controlled trial. To investigate whether preoperative using of eye patches will decrease emergence agitation or not, and to provide a better method of decreasing emergence agitation to pediatric ophthalmic anesthesiologists. The investigators will recruit 180 children undergoing elective cataract surgery, divided into 2 groups by random method. experimental group will cover the effected eye for 3 hours before the operation, while the control group will not. Then the investigators will observe and mesure the incidence of emergence aditation in each group, to assess whether preoperative patch shading can reduce the incidence of postoperative agitation.

Inclusion Criteria:

1. Preschool patients undergo elective cataract surgery, whose age are 3 to 7 years.
2. Patients' parents agree to participate in the trial, and sigh the informed consent.

Exclusion Criteria:

1. Patient who can not communicate with medical workers preoperatively.
2. Both of patient's eyes are covered postoperatively.
3. Patient's parents refuse to sign informed consent.
4. The investigators do not think such patient is suitable for our research
5. The patient has serious arrhythmia, abnormal cardiac defect.
6. The patient has suffered from pneumonia, asthma symptoms, bronchitis, or upper respiratory tract infection recent two weeks.
7. The patient has serious disease of the nervous system.
8. The patient has the allergic history of any drug involved in this clinical trial.