The current range of normal intraocular pressure (IOP) is 10 to 21 mmHg, with a mean IOP of 15.8 mmHg. Normal intraocular pressure is actually a general statistical result that is informative, but does not mean that anything outside this range is necessarily abnormal. IOP is the pressure of the contents of the eyeball acting on the wall of the eyeball and the interaction between the contents. The normal range of IOP is about 10 to 21 mmHg, beyond which it may be abnormal. The role of IOP is mainly to maintain the morphology of the eyeball and normal physiologic function. There are two ways to measure IOP: finger-measured IOP and tonometer measurement. If a patient’s IOP is elevated, it may be caused by glaucoma, and elevated IOP is an important manifestation in the diagnosis of glaucoma patients. Glaucoma patients may experience inappropriate eye swelling, nausea and headache. It is recommended that patients with abnormal intraocular pressure seek prompt medical attention to assess their condition and follow doctor’s instructions for treatment.