Glaucoma is second only to cataracts as the leading cause of vision loss worldwide. It is characterized by increased intraocular pressure, optic nerve atrophy and visual field defects. The most important hazard of glaucoma is visual impairment, which manifests itself as a loss of vision and a reduction in visual field defects. Visual acuity loss usually occurs during 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 can reduce visual acuity to light perception. The occurrence of visual field defects is insidious and progressive, especially in primary open-angle glaucoma, where the early clinical manifestations are not easily detected, and once vision loss is detected and seen, it is often at an advanced stage of the disease. The loss of vision and visual field defects caused by this type of glaucoma cannot be reversed and restored by the current medical technology. Therefore, early detection and timely treatment is a key to prevent glaucoma blindness.