Various species of Pilocarpus are a source of the parasympathomimetic alkaloid Pilocarpine. Pilocarpine eye drops are used for glaucoma. They are most often used to treat acute angle-closure glaucoma, when pressure inside the eye rises too high too quickly. Philocarpine works by causing your pupil to constrict which opens the drainage channels in the eye, allowing fluid to leave the eye and thus relieving pressure.