Purpose: The purpose of this study is to compare therapeutic effects of oral acetazolamide versus Cosopt drops to prevent increase in intraocular pressure after Nd-YAG laser in posterior capsulotomy. Plan: A block-randomized, single-blind, placebo-controlled Clinical Trial, Phase II. Inclusion criteria: patients with age over 40 years who have undergone phacoemulsification surgery at least 3 months ago, and have posterior capsule opacity. Exclusion criteria: Patients with asthma and pulmonary obstructive diseases, medication side effects, retinopathy, severe corneal opacity, occurrence of intraoperative complications, history of glaucoma, uveitis, absence in the follow up, and traumatic cataract. Interventions: First group will receive oral acetazolamide with placebo drops, and the second group will receive Cosopt drops with oral placebo. Primary outcome: Reduction in intraocular pressure.