Understanding Eye Pressure
The eyeball is like a basketball or a tire, and in this way it has a pressure. Fluid (called aqueous humor) is made inside the back portion of the eye called the "ciliary body". This fluid is created inside the eye, and nourishes the eye. It slowly travels from the back part of the eye to the front of the eye to an area called "the angle" or "trabecular meshwork", where it then exits the eye.
Elevation of your eye's pressure is never caused by too much fluid being made. The elevation in your eye's pressure is caused by blockage to the drainage area of your eye (the angle or trabecular meshwork).
Glaucoma can cause blindness if left untreated. Lowering the pressure in the eye, either by using eye drops, laser surgery, or actual incisional surgery can prevent the progression of glaucoma, thus sparing vision.
If our doctors determine that the pressure in your eye should be lowered, they will first determine what an appropriate goal, or target pressure should be. Following that they will use therapies that do one of the following:
- Decrease the amount of fluid which is made. (This is similar to turning off a faucet of a sink which may be overflowing).
- Increasing the amount of fluid which the drainage system allows to leave the eye (this is similar to using Liquid Plumber®).
The pressure always changes and can vary quite a bit, especially in glaucoma patients. This is neither abnormal nor surprising. One can imagine that the "thermostat" within the eye which sets and regulates the eye's pressure does not work as well in eyes with glaucoma. A single pressure reading can be deceiving or misleading. The doctor might therefore place more emphasis on evaluations of the optic nerve appearance and how the eye functions when performing a visual field than one specific eye pressure reading.
There is no known relationship between eye pressure and stress or tension. Eye pressure is not related to caffeine use. Eye pressure and blood pressure are NOT related. The only exceptions to this are as follows:
- In younger individuals, it may be less likely for a person to have both glaucoma and high blood pressure.
- However, in older individuals, it may be more likely for people to have both high blood pressure and glaucoma.
- Some medications which lower your blood pressure may also lower your eye pressure.
To measure eye pressure, an eye drop, which might sting for a few seconds, is placed on your eye. This numbs your eye. A probe is next placed on your eye which measures the pressure inside of it. The pressure inside your eye is related to how much force is needed to indent your cornea just a little bit. This process does not hurt and only takes a matter of seconds!
There is no such thing as a “normal” eye pressure. Each person and each eye has a unique threshold above which damage to the optic nerve develops. Therefore we have to develop an individualized treatment plan for each patient. Your ideal pressure may be higher or lower than your neighbors.