An IOP test is a very routine test in ophthalmology, which is a machine that detects the pressure in the eye, and is just a test that does not include any items. The IOP test is mainly used to diagnose glaucoma, which is a series of pathological damages caused by pathologically elevated intraocular pressure, and one of the important diagnostic bases is the intraocular pressure. Under normal circumstances the normal value of IOP should be between 8-21 mmHg. If the IOP exceeds 21 mmHg and after fundus examination has shown signs of optic nerve damage, such as a larger cup-to-disc ratio and visual field defects, it can be diagnosed as glaucoma, which is an ophthalmic emergency and must be actively given symptomatic treatment to lower IOP to avoid further aggravation of optic nerve damage.