Carbachol is a cholinergic drug, which means it causes parasympathetic effects in the eye. The autonomic nervous system, which controls reflex actions in the body, consists of the sympathetic and parasympathetic nervous systems .Carbachol is administered for eye conditions in two forms, an intraocular injection used during cataract surgery and an ophthalmic drop used to treat glaucoma.
Decreased Eye Pressure
Pupil constriction caused by the parasympathetic action of carbachol helps decrease intraocular pressure (IOP) in glaucoma. There are two types of glaucoma that cause optic nerve damage: open-angle, and narrow, or closed-angle. Carbachol decreases eye pressure in both open-angle and closed-angle glaucoma, according to Drugs. Com.
IOP is controlled by the flow of aqueous humor (fluid) from the eye. If fluid can't flow freely through the trabecular meshwork, found at the junction of the iris and cornea, the amount of fluid in the eye increases and the IOP rises. Carbachol increases aqueous humor flow by constricting the iris and contracting the ciliary body, which opens the trabecular meshwork and allows fluid to exit, according to Drugs.com.
Complications of Intraocular Injection
According to Carbastat (intraocular injection)--a brand name for carbachol--intraocular carbachol can cause clouding or swelling of the cornea, retinal detachment and inflammation of the iris called iritis after injection for cataract surgery.
Complications of Ophthalmic Drops
According to the Mayo Clinic, blurred vision, eye pain and burning or stinging in the eye may occur with carbachol ophthalmic drops. According to Healthline, carbachol can also increase poor vision in dim light, lens clouding and cataract progression, and may cause a transient rise in IOP before the IOP drops.
