Normal IOP and factors affecting IOP: The pressure exerted by the contents of the eye on the wall of the eye is called intraocular pressure (IOP for short). The intraocular pressure that maintains normal visual function is called normal intraocular pressure. Under normal conditions, the rate of atrial aqueous production, the rate of atrial aqueous drainage and the volume of ocular contents are in dynamic equilibrium, which is an important factor in maintaining normal IOP. If the dynamic balance of these three is out of balance, pathological IOP will occur. The majority of our normal IOP values are between 1.33 and 2.79, more than 3.19kpa (24mmHg) is pathological, between 2.79-3.192kpa (21-24mmHg) is suspected pathological IOP. However, 4.55% of normal people have an IOP above 3.192kpa (mean ± 3 standard deviations) without glaucoma status, in other words, these people have an IOP that exceeds the high limit of normal, but the optic nerve has not suffered damage. Therefore, one value cannot simply be used as a criterion for classifying pathological IOP. It is more appropriate to divide IOP into three ranges: normal, suspected pathological and pathological. Range of pathologic IOP: If any part of the atrial water channel is obstructed, it will lead to an increase in IOP. In normal people, IOP fluctuates slightly during the 24 hours of the day, generally the lowest in the evening, gradually rising after resting at night, to the highest in the morning before waking up, and slowly falling after getting up and moving around, with IOP fluctuations not exceeding 0.665kpa (5mmHg), and bilateral IOP is basically equal, or not much different. If the 24-hour IOP is 1.064kpa (8mmHg) and the highest IOP exceeds 2.793kpa (21mmHg) or the difference between the two eyes is greater than 0.665kpa (5mmHg), it should be considered abnormal and requires further examination. High IOP and optic disc microcirculation disorders are the main causes of glaucomatous optic disc sulcus and visual field damage. Although high IOP is an important factor in glaucoma damage, it is not absolute. In clinical practice, some patients with IOP beyond the statistically high limit of normal, but do not develop optic disc and visual field damage after long-term observation, are called hypertelorism. There are also a few patients with IOP in the normal range or critical value, while optic disc and visual field damage has been very obvious. This type of glaucoma is called low IOP glaucoma or normal IOP glaucoma.