Once the intraocular pressure exceeds 21mmHg, it is necessary to be vigilant, because the normal intraocular pressure should be lower than 21mmHg. The causes of the elevated intraocular pressure may be over-exertion of the eyes, glaucoma and so on. 1. Excessive use of the eyes: Sometimes prolonged excessive use of the eyes can lead to increased intraocular pressure, in this case, you need to rest and relax the eyes, and the intraocular pressure will return to normal after a period of rest. 2. Glaucoma: under normal circumstances, the eye will secrete aqueous humor, when suffering from glaucoma, it will lead to the circulation of aqueous humor is impaired, which will lead to increased intraocular pressure, intraocular pressure is not well controlled will compress the optic nerve and lead to vision loss. Eye pressure beyond the normal value may also be other reasons, must go to the hospital in a timely manner to improve the examination, to clarify the cause, and follow the doctor’s instructions to deal with, so as to avoid delaying the condition.