Used primarily in the treatment of glaucoma to reduce intraocular pressure by inhibiting the enzyme acetylcholinesterase, which increases the levels of acetylcholine in the eye. It is also employed in the management of anticholinergic toxicity, where it acts as a reversible acetylcholinesterase inhibitor to counteract the effects of anticholinergic drugs. Additionally, it has been explored for its potential in improving cognitive function in conditions like Alzheimer's disease, though its use is limited due to side effects. In ophthalmology, it is sometimes used to constrict the pupil during certain surgical procedures.