The causes of low IOP are ocular trauma, drops of IOP-lowering medications, glaucoma surgery, etc., as follows: First, ocular trauma, ocular trauma causing low IOP has the following possibilities: 1, reduced atrial fluid secretion, due to traumatic shock, resulting in paralysis of the atrial fluid-secreting cells of the ciliary muscle and reduced secretion of atrial fluid. 2, consider excessive drainage, such as suprachoroidal chamber drainage, because trauma may cause the atrial angle to 3. Consider poor drainage, such as suprachoroidal drainage, because trauma may cause the atrial angle to rupture, resulting in atrial fluid entering the suprachoroidal space through these fissures, which can lead to low IOP. 3. Second, low IOP can be caused by drops of IOP-lowering drugs, such as Meclizine, which can lead to lower IOP. Thirdly, after glaucoma surgery, the establishment of an external drainage port and excessive drainage can also lead to low IOP.