Glaucoma is the leading cause of irreversible vision loss, worldwide. The term glaucoma includes many different diseases, which are associated with differing risk factors, symptoms, treatment, and prognosis. All forms of glaucoma are characterized by the loss of the retinal ganglion cells and their axons that make up the optic nerve, which results in a cupping of the optic nerve head. This leads to optic nerve damage and visual field loss. Raised intraocular pressure (IOP) is the primary risk factor for glaucoma, and progression of disease will normally stop if the IOP is lowered by 30-50%. Consequently, treatment options for glaucoma are developed around lowering the IOP. Although it is possible to slow the progression of glaucoma using current treatment options, it is not possible to reverse vision loss that has resulted from the disease.
Most drugs prescribed for glaucoma can be placed into one of four drug classes. Prostaglandin analogues (PGAs) are generally used as a first-line treatment, with beta blockers (BBs), alpha adrenergic receptor agonists (AAs), and carbonic anhydrase inhibitors (CAIs) also frequently used, albeit generally as second-line therapies in combination with PGAs. Certain combinations of available drugs are marketed as part of fixed-dose combination (FDC) therapies. Cholinergic agonists, also known as miotics, can also be used for the treatment of glaucoma, although they are much less commonly prescribed compared with PGAs, BBs, AAs, and CAIs.