There is a clinical category of normal intraocular pressure glaucoma in which patients are confused as to why they have glaucoma when their IOP is normal. These patients always have an IOP between 10 and 21 mm Hg, but do have optic nerve damage and visual field defects. In fact, the so-called normal is relative, for most people, the IOP in this case is normal; but for the patient this “normal” IOP is already abnormal and has caused optic nerve damage, so normal IOP does not necessarily mean that it is not glaucoma. So does high IOP necessarily mean glaucoma? Not necessarily. Some people are born with high IOP, perhaps 25 mmHg, and have no damage to the optic nerve or visual field at the fundus during years of follow-up, so they are diagnosed as having high IOP. High IOP is not really glaucoma, only about 10% or so of patients will develop glaucoma later, most of the patients with high IOP are normal. So don’t be nervous when you find abnormal eye pressure. Make sure to see your doctor to help you determine if you have glaucoma through tests.