What does it mean to have dangerous eye pressure?

Above 30 or so: Normal eye pressure is up to 22 mm hg. About 30 we get concerned about slow glaucomatous damage and much above 40 is considered an emergency.

Glaucoma: When the eye pressure is high enough to cause permanent damage to the optic nerve it is dangerous. The higher it is, the more dangerous because the damage will occur much quicker.