A 16-year-old boy presents to the emergency department 2 hours after blunt ocular trauma from a cricket ball. Slit-lamp examination reveals the structure marked **A** — layered blood in the inferior anterior chamber occupying approximately 40% of the chamber height. Visual acuity is hand motions. Intraocular pressure is 28 mmHg. On further history, the patient is of African descent. Which of the following is the MOST critical next step in the management of this patient's hyphema?