Glaucoma is a group of eye diseases characterized by typical optic nerve atrophy and visual field defects, with high intraocular pressure and visual field loss as features. Clinically, some patients have long-term high intraocular pressure but do not exhibit optic nerve and visual field damage. This condition is not called glaucoma, but is referred to as ocular hypertension. Meanwhile, some patients may have normal eye pressure but still exhibit typical glaucoma optic nerve damage and visual field defects; this condition is called normal-tension glaucoma. Therefore, high intraocular pressure does not necessarily indicate glaucoma, and normal intraocular pressure can also potentially be glaucoma.