If high IOP causes optic nerve atrophy and damage to visual function (loss of vision and reduced visual field), it is medically called glaucoma. If only the IOP is high without optic nerve atrophy and visual impairment, glaucoma cannot be diagnosed and should be called hyperopia. If the IOP is not high (normal) but there is glaucomatous optic nerve atrophy and visual impairment, and other brain disorders are excluded, it is called normal IOP glaucoma, which also needs treatment.