Eye (Intraocular) Pressure

What is intraocular pressure?

“Intraocular pressure” is the medical term for the pressure of the fluid inside of your eyes. You might see it referred to as eye pressure or IOP. Your naturally occurring intraocular pressure is an important part of your vision and your eyes’ physical health.

Your eyes are filled with fluid. The chamber at the back of your eye is filled with vitreous humor (a thick, gel-like material). A liquid called aqueous humor fills the area at the front of your eye (the space between your cornea and iris). Aqueous humor is thinner and waterier than vitreous humor.

Your body regulates your intraocular pressure automatically. As your eye creates new aqueous humor, an equal amount of older aqueous humor leaves your eye. Old aqueous humor runs out of your eye through the drainage angle — the spot where your iris (the colored part of your eye) meets the sclera (the white part of your eye).

Having high intraocular pressure is a health condition called ocular hypertension. If it’s not treated, this added stress on the parts inside your eye can damage your optic nerve. Untreated ocular hypertension can cause glaucoma and make you permanently lose your vision.

How is intraocular pressure measured?

An eye care specialist will check your intraocular pressure during an eye exam.

Intraocular pressure is the amount of pressure or force inside of your eyes. Specifically, it’s a measurement of the fluid pressure in your aqueous humor.

An eye care specialist will measure your eye pressure with a test called tonometry. Tonometry measures the pressure inside of your eye by flattening your cornea (the clear part at the front of your eye). The more force that’s needed to flatten your cornea, the higher your eye pressure is.

The most common type of tonometry is non-contact or air puff tonometry. A machine shoots a brief puff of air against your eye and measures how much your cornea moves.

Your eye care specialist might also measure your intraocular pressure by numbing your eye with special drops, and then pressing a tool against your cornea.

What is the average eye pressure?

Eye care specialists measure eye pressure in millimeters of mercury. You might see this referred to as mmHg (Hg is the chemical symbol for mercury). It’s the same measurement healthcare providers use when they’re checking your blood pressure.

A healthy amount of intraocular pressure is between 10 mmHg and 20 mmHg.

What causes high eye pressure?

Your body automatically adjusts your eye pressure. But certain changes inside your eye can affect your intraocular pressure faster than your body can regulate it, including:

• Your eye producing too much aqueous humor.
• A blocked drainage angle that prevents aqueous humor from leaving your eye.
• Traumas and eye injuries.
• Side effects from some medications, especially corticosteroids.

People with high intraocular pressure have an increased risk of developing glaucoma. Ask an eye care specialist how often you should have your intraocular pressure checked.

What does high eye pressure feel like?

Ocular hypertension usually doesn’t cause any symptoms. You probably won’t know you have high eye pressure until an eye care specialist diagnosis it during your eye exam.

Without having your eye pressure tested by an eye care specialist, there’s usually no way for you to feel or know that you have high eye pressure. It doesn’t cause symptoms until it’s damaged your optic nerve enough to affect your vision. That’s why it’s important to have your eye pressure checked regularly.

How is high intraocular pressure treated?

An eye care specialist will treat high eye pressure. Which treatment you’ll need depends on how high your intraocular pressure is and what’s causing it. Some treatments include:

• Medication (usually eye drops) that decrease fluids and increase drainage in your eye.
• Laser treatment to clear a blocked drainage angle.
• Surgery to relieve pressure inside your eye.

Your eye care specialist will monitor you for signs of glaucoma. They’ll tell you how often you need your eye pressure checked.

When should I visit my healthcare provider?

Visit an eye care specialist as soon as you notice any of the following symptoms:

• Changes in your vision.
• Eye pain.
• Severe headaches.

Go to the emergency room if you suddenly lose sight or if you see new floaters or flashes.

Is high blood pressure the same as high eye pressure?

High blood pressure (hypertension) and high eye pressure (ocular hypertension) aren’t the same condition. If you have high blood pressure, you might also have high intraocular pressure, but one doesn’t cause the other.

Even though it doesn’t cause higher eye pressure, people with high blood pressure have an increased risk of developing glaucoma. Talk to an eye care specialist about your glaucoma risk if you have high blood pressure or are receiving treatment for high blood pressure.

Can blood pressure affect my vision?

Your blood pressure can affect your vision. If your blood pressure is too high or too low, your optic nerve might not get the supply of fresh blood it needs to work properly. If the issues with your blood pressure aren’t treated, they can eventually damage your optic nerve and affect your ability to see clearly.

A note from Cleveland Clinic

Your intraocular pressure is the naturally occurring pressure inside of your eyes. Your eyes are usually good at regulating this pressure automatically. But if something affects the natural flow of aqueous humor in and out of your eyes, your intraocular pressure can rise.

High eye pressure doesn’t usually cause symptoms until it’s damaged your eyes enough to cause glaucoma. Visit an eye care specialist regularly. They’ll check your eye pressure as part of your routine eye exam and catch any changes before they can damage your eyes.