Intraocular Pressure and Your Eye Health

At your regular eye exam, one thing your eye doctor always checks is your intraocular pressure. It gives an important picture of your eye health and can find signs of optic nerve damage that might affect your eyesight.

Your eyes are filled with fluid that helps keep them inflated like a ball. The “normal” pressure in the eyes can change during the day and differ from person to person. In healthy eyes, the fluids drain freely to keep the eye pressure steady.

If your eye pressure is consistently too high or too low, it could be a warning that you may have problems with your vision.

Eye Pressure Check

A tonometry test measures your intraocular pressure. It’s like pressing a balloon to check for air. It shows how firm your eyeball is with the same measurement units used to check blood pressure. The normal range for intraocular pressure is about 10-20 mm HG.

The test is done in a couple of ways. Your doctor may touch your eye with the tip of a tool. You may get numbing eye drops first. Rarely, your doctor might give you a quick puff of air onto the eye.

Why Eye Pressure Matters

Normal intraocular pressure helps support the shape of the eye, which in turn supports the 2 million parts of the eye that help you see.

High pressure. When the fluid in the front of your eye doesn’t drain as well as it should, or your eye is producing too much fluid, pressure can get too high. Your doctor may call this ocular hypertension.

It can lead to glaucoma, a group of eye diseases that causes blindness. High eye pressure is one of the top reasons people get it. Glaucoma doesn't cause pain, and you can have it for years without noticing any changes in your vision. So checking for high eye pressure can help you catch it early.

You might get ocular hypertension after an eye injury or disease. Some medications, such as steroids, also can raise your eye pressure. It might also happen after certain medical procedures, such as when you get a tube put into your throat. If yours is already high, a spike may damage your vision.

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Low pressure. This is a less common concern than high eye pressure. Often, people get low pressure because of a leak in the eye after surgery.

For some people, very low pressure can bring on blurry vision or other problems. Others can see just fine with it.

When the pressure is below 5 mm HG, doctors call it ocular hypotony. It can make you more likely to get several eye problems, including:

  • Swelling in the cornea, the clear outer dome of your eyes
  • Cataracts
  • Damage to the macula, the light-sensing part of the retina that allows you to see
  • Discomfort

Unlike with blood pressure, the danger zones for eye pressure can be tricky to pin down. People can have different ranges for what’s normal. One in 3 people with glaucoma never have “high” eye pressure, while others can have higher-than-normal pressure without damaging their optic nerves. That’s one reason for you to see an ophthalmologist or optometrist regularly.

WebMD Medical Reference Reviewed by Whitney Seltman on September 06, 2019

Sources

SOURCES:

American Academy of Ophthalmology: “What is Eye Pressure?” “Eye Exams 101,” “What is Low Eye Pressure and Does it Cause Any Damage to Your Eyes?” “What is Ocular Hypertension?”

Continuing Education in Anaesthesia, Critical Care & Pain: “Intraocular pressure.”

Merriam-Webster Medical Dictionary: “mm Hg.”

Discovery Eye Foundation: “20 Facts About the Amazing Eye.”

Medscape: “Hypotony.”

Glaucoma Foundation: “Frequently Asked Questions.”

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