What is Normal Eye Pressure?

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  • Written By: N. Freim
  • Edited By: Melissa Wiley
  • Last Modified Date: 05 September 2019
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During an eye exam, a tonometer will measure the pressure of the fluid behind the cornea. To be considered normal eye pressure, the measurement should be between 10 to 20 mmHg. The reading can vary by body position, time of day, and factors like medication or fluid intake. An increased pressure can be a warning sign of problems, most notably glaucoma.

The cornea of the eye is filled with a thick liquid called the aqueous humor. This fluid helps keep the cornea curved and inflated. The eye constantly produces new aqueous humor and drains the old. The pressure of the fluid is measured with a tonometer, which gauges the amount of force needed to flatten an area of the cornea. The thickness of the individual cornea can affect the results.

There are a variety of ways to measure eye pressure. Some tonometers involve direct contact with the eye, which usually requires a topical anesthetic, and are regarded as the more reliable method. Several non-contact methods involve a tonometer that pushes a puff of air at the cornea and measures the force of the air as it hits. This style is good for children or people who are nervous about having a machine touch their eyes.


The tonometer measures normal eye pressure in millimeters of mercury (Hg). The healthy range is from 10 to 20 mmHg, with the average being about 14 to 16 mmHg. The amount of pressure can vary throughout the day and can change depending on the position of the body. Factors that normally affect general health, such as exercise, medicine, or alcohol intake, can also affect eye pressure.

Although normal eye pressure usually increases with age, a marked increase or a difference in pressure in each eye can be warning signs for health problems. High pressure is often seen with glaucoma, although the disease can develop without it. Eye pressure above 21 mmHg can damage the optic nerve and can lead to blindness. If glaucoma is caught early, doctors may be able to slow the disease. Once the eye is damaged, however, it is difficult to repair. This is why it is important to have regular checkups to measure normal eye pressure and catch problems early.


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Post 2

@raynbow- I have the same medical issue, and your friend's doctor is doing the right thing by monitoring her elevated eye pressure. Just because it is borderline high does not mean that she will develop glaucoma, and having any type of treatment at this point would probably do more harm than good.

On the other hand, your friend's condition could eventually lead to that diagnosis. By having her eye pressure monitored annually, her doctor will be able to notice changes, and provide treatment if and when necessary.

There are some things that your friend can do to make sure that she take good care of her eye health. She should always be sure to keep her annual appointment

with her ophthalmologist so he or she can document any changes in her eye pressure. Also, if she ever develops any changes in her vision or any other troubling symptoms, she should have them checked out as soon as possible so she can get prompt treatment if her eye pressure ever rises to concerning levels.
Post 1

I have a friend who doesn't have a diagnosis of glaucoma, but goes to her ophthalmologist every year to have her eye pressure checked. Her doctor told her that it is borderline high, but I am concerned for her and wonder if she is getting the best medical care. Does high eye pressure always eventually turn into glaucoma, and should my friend be doing more for her eye pressure issues?

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