Why can primary open-angle glaucoma cause vision loss without pain?

Primary open-angle glaucoma (POAG) is characterized by a slow, progressive form of optic nerve damage that does not trigger the acute physical symptoms associated with other forms of the disease, such as angle-closure glaucoma.1

Unlike angle-closure glaucoma, where a sudden blockage causes a rapid, painful rise in intraocular pressure—often resulting in eye pain, headaches, and nausea—the progression of POAG is gradual. Because the damage to the optic nerve occurs slowly over time, it does not cause immediate pain or discomfort. Furthermore, early vision loss in POAG typically affects the peripheral visual field, leaving central vision intact until the later stages of the disease.12

Because symptoms are often slight or absent in the early stages, POAG is frequently described as a silent condition. This makes regular screening for intraocular pressure essential, as early diagnosis is the only way to implement treatments that prevent further, irreversible vision loss.12