Patients having cataract extraction in the second eye under topical anesthesia with monitored anesthesia care often report increased pain and awareness relative to the first surgery in the fellow eye, despite similar operative and anesthetic conditions. The purpose of this study is to investigate the pathogenesis of this phenomenon.

Inclusion Criteria:

• Age-related cataract patients aged 50 years or older able to give informed consent undergoing cataract surgery;
• Pupil dilation ≧7 mm after mydrisis;
• VA prognosis ≧6/12

Exclusion Criteria:

• Unable to give informed consent;
• Patients with history of ocular pathology or diabetic retinopathy;
• Patients with traumatic, subluxated and posterior polar cataract;
• Patients had other ocular surgery (not cataract surgery) in the past 6 months;
• Patients with significant intra-operative complications