Glaucoma is a group of eye diseases that can lead to damage of the optic nerve and gradual loss of vision. The most frequently occurring type is open-angle glaucoma, but there are also less common forms such as closed-angle glaucoma and normal-tension glaucoma. Open-angle glaucoma progresses slowly and is typically not accompanied by pain. Initially, individuals may notice a reduction in their peripheral vision, which can eventually lead to central vision impairment and, if left untreated, blindness. On the other hand, closed-angle glaucoma can manifest gradually or suddenly, with the sudden onset involving intense eye pain, blurred vision, a partially dilated pupil, eye redness, and feelings of nausea. Once vision loss due to glaucoma occurs, it is irreversible.