Glaucoma is a leading cause of blindness in the United States and globally. Open-angle glaucoma is an acquired loss of retinal ganglion cells characterized by either normal or increased intraocular pressure, a large cup-to-disc ratio, and visual field defects. Open-angle glaucoma is treated by reducing intraocular pressure, most commonly with eye drops. Angle-closure glaucoma, which is much less common, is an acute increase in intraocular pressure from a mechanical obstruction that must be treated emergently to preserve vision.