A 58-year-old woman presents to the emergency department with acute onset of severe eye pain, blurred vision, and nausea for the past 6 hours. On examination, the right eye shows a mid-dilated pupil, corneal edema, conjunctival injection, and an intraocular pressure (IOP) of 58 mmHg. Gonioscopy reveals a closed angle. What is the most appropriate immediate next step in management?