Demecarium bromide is primarily used in ophthalmology as a long-acting cholinesterase inhibitor. It is applied in the treatment of glaucoma to reduce intraocular pressure by constricting the pupil and contracting the ciliary muscle, thereby increasing the outflow of aqueous humor. Additionally, it is used in the diagnosis and management of accommodative esotropia, a condition where the eyes turn inward due to excessive accommodation, by inducing miosis and cycloplegia to reduce accommodative convergence and improve eye alignment. Its prolonged action makes it suitable for less frequent dosing, providing convenience for patients requiring long-term therapy.