Glaucoma is the second most common cause of legal blindness in the United States. Open-angle glaucoma is an asymptomatic, progressive optic neuropathy characterized by enlarging optic disc cupping and visual field loss. Patients at increased risk for open-angle glaucoma include blacks older than 40 years, whites older than 65 years, and persons with a family history of glaucoma or a personal history of diabetes or severe myopia. Elevated intraocular pressure is a strong, modifiable risk factor for open-angle glaucoma, but it is not diagnostic. Some patients with glaucoma have normal intraocular pressure (i.e., normal-pressure glaucoma), and many patients with elevated intraocular pressure do not have glaucoma (i.e., glaucoma suspects). Routine measurement of intraocular pressure by primary care physicians to screen patients for glaucoma is not recommended. Open-angle glaucoma usually is discovered during an adult eye evaluation performed for other indications. Final diagnosis and treatment occur in collaboration with ophthalmologists and optometrists. Formal visual field testing (perimetry) is a mainstay of glaucoma diagnosis and management. Eye drops, commonly nonspecific beta-blocker or prostaglandin analog drops, generally are the first-line treatment to reduce intraocular pressure. Laser treatment and surgery usually are reserved for patients in whom medical treatment has failed. Without treatment, open-angle glaucoma can end in irreversible vision loss.