Intraocular pressure is the pressure of the contents of the eye against the wall of the eye. The normal value of IOP is a statistic that corresponds to approximately 95% of the normal population physiologically and is normally between 10 and 21 mm Hg. IOP is elevated when it exceeds 21 mm Hg. However, there is a distinction between physiological IOP elevation and pathological IOP elevation. In physiological IOP elevation, the IOP is higher than the normal range but there is no organic pathology in the eye that requires treatment. Since the IOP measurement device is affected by the thickness of the cornea, a thicker cornea may result in a higher IOP measurement, but the actual IOP may not be high. Pathologic IOP elevation can be caused by a variety of factors. In acute or chronic angle-closure glaucoma, for example, the atrial angle is closed, affecting the flow of atrial fluid and thus causing an increase in IOP. Trauma to the eye that causes blood to accumulate in the anterior chamber or changes in the structure of the atrial angle can cause an increase in IOP. Some ophthalmic surgeries can also cause IOP elevation, such as residual viscoelastic or residual lens cortex after cataract surgery. Glaucoma trabeculectomy can also cause IOP elevation if the follicle formation is not optimal. In conclusion, IOP elevation can be physiologically or pathologically induced. Physiologic IOP elevation can be left untreated, while pathologic IOP elevation requires different treatment measures according to the specific situation.