What exactly is acute glaucoma?

Fluid block in eye: The eye has an internal clear fluid circulation 24/7. This is called the aqueous humor. The iris in certain shaped eyes (usually farsighted) can obstruct the outflow and within 1/2 hour the pressure can skyrocket to dangerous levels. This is an emergency, can be stopped with certain drugs and prevented with laser. See your ophthalmologist immediately if you suspect this condition.

Aka Angle Closure: Most glaucomas have no symptoms until they become severe. In acute angle closure there may be pain, blurred vision and redness. This is caused by a rapid rise in eye pressure and if untreated may result in permanent vision loss.