Glaucoma is a group of eye conditions that cause progressive damage to the optic nerve head, which can lead to vision problems and irreversible vision loss if it is not treated early. It is typically classified as open angle or closed angle and primary or secondary.

Open-angle glaucoma typically has no early symptoms, and visual issues like needing more light and blurry vision develop gradually. In contrast, closed-angle glaucoma can be asymptomatic or occur within a short period of time, with symptoms such as intense eye pain, blurry vision, and nausea due to a sudden increase in eye pressure.

Glaucoma is diagnosed through a complete eye exam that includes 5 tests: tonometry for intraocular pressure, pachymetry for corneal thickness, ophthalmoscopy for optic nerve examination, perimetry for visual field assessment, and gonioscopy for measuring the anterior chamber angle. These tests help determine the presence and severity of glaucoma.

The main medical treatments for glaucoma focus on lowering elevated intraocular pressure, which is the only treatable risk factor for the condition. This can be achieved through medications, laser treatment, surgery, or a combination of these approaches.

Limited preliminary evidence indicates that certain supplements — such as Ginkgo biloba, blackcurrant anthocyanins, epigallocatechin-gallate, vitamin B3, and Erigeron breviscapus — may have beneficial effects on glaucoma by reducing intraocular pressure and improving retinal function.

Dietary patterns and components have a limited and often conflicting relationship with glaucoma risk, but eating fruits and vegetables that are high in vitamin A, carotenes, and nitrate may reduce risk. Additionally, although caffeinated tea may be associated with lower glaucoma risk, caffeine in coffee can temporarily raise intraocular pressure in people with glaucoma.

Some nonmedical treatments for glaucoma — such as exercise, cannabis, acupuncture, and relaxation techniques — have been studied, but their effectiveness varies. Although cannabis can reduce intraocular pressure, its effects are temporary, and there is insufficient evidence to support acupuncture and relaxation techniques.

The exact causes of primary glaucoma are not fully understood, but it is often associated with intraocular pressure levels and may also involve factors such as insufficient oxygen supply to the optic nerve, excessive glutamate stimulation, and the presence of free radicals and inflammatory cytokines. These factors can contribute individually or collectively to damage from glaucoma.