Eye Pressure, which is also called Intraocular Pressure (IOP), is pressure in the eye which keeps the eye in a distorted state. There is no bone in the eye and it keeps itself taut by this pressure. There is fluid in the eye which is being formed continuously and it is being cleared also simultaneously.
There is a fine balance between the formation and egress of fluid. 



It can be measured with machines (Tonometer). It is ideally between 10-21 mm Hg of mercury. When there is any problem in the formation or clearence  of fluid, diseases of eyes occur. In Glaucoma, there is either excess of fluid formation or clearence of fluid is less. In cases, the pressure of eyes increases and this causes compression on the optic nerve. Glaucoma is caused by the imbalance of intraocular pressure. The drug used to treat Glaucoma also either decreases the formation of aquous or increases the clearance of aqueous.

The pressure has a correlation with blood pressure. If blood pressure increases, eye pressure also increases. In some yoga asanas, there is also an increase in eye pressure. Drinking more water also increases eye pressure.

Control of eye pressure is very important in many eye diseases such as uveitis. Clearance of fluid is sometimes decreased due to the pressure of RBC (blood cells) after trauma.

If the pressure of the eye is not maintained by medicine then surgery has to be done to decrease the pressure. It is very important to monitor the eye pressure in all the diseases mentioned above and its long term control can control the disease process.