Glaucoma is one of the most common blinding diseases, characterized by elevated intraocular pressure, optic nerve atrophy and visual field defects. In most cases, the cause of optic nerve damage is primarily high intraocular pressure, while in a few patients it occurs at normal intraocular pressure, called normal intraocular pressure glaucoma. Although the clinical features of glaucoma are diverse, the most important hazard is visual impairment, which manifests as vision loss and visual field defects. Visual acuity loss usually occurs in acute high IOP. The initial stage of visual acuity loss is due to high IOP that prevents the corneal endothelium from draining water from the cornea normally, as a result of which corneal epithelial edema occurs; acute persistent high IOP, which can reduce visual acuity to light perception, is due to very high IOP that seriously affects the metabolism of the optic cells. Chronic high IOP and persistent high IOP later cause optic nerve atrophy, resulting in visual field defects. Because of the insidiousness and progressiveness of visual field defects, especially in primary open-angle glaucoma, the early clinical manifestations are not obvious or not specific enough to be easily detected, and once vision loss is detected and seen, the disease is often advanced and the visual field defects are severe and unrecoverable. Therefore, glaucoma emphasizes early detection and timely treatment. Do not take a chance and delay the time of treatment.