What is Intraocular Pressure (IOP)?

by | Feb 16, 2021 | Eye Health | 0 comments

Have you ever noticed your eye doctor talk about IOP at your eye exam? Or perhaps you’ve heard about it from a family member with glaucoma and wondered what they were talking about. Either way, Nanodropper has got you covered! Read on to learn what intraocular pressure is, and why it’s an important measurement for your eye health.

Intraocular Pressure, or IOP for short, is the pressure inside of your eyeball.

Similar to how a ball is inflated with air, your eye is filled with fluid. This fluid presses against the inside walls of the eye, creating a pressure which is measured in millimeters of mercury (mm Hg).

So what exactly is a normal IOP? 

According to the American Academy of Ophthalmology, a normal IOP is between 10-20 mm Hg, though wide variation exists. Serious conditions such as glaucoma can occur at seemingly “normal” pressures. As such, it is extremely important to monitor eye health with routine exams by your eye care provider.

Healthy eyes create new fluid while simultaneously draining an equal amount of fluid through an outflow system including the angle of the eye, where the cornea (clear window of the eye) and iris (colored part) come together. This regulation keeps the pressure inside the eye the same.

What if your IOP is outside of this range?


An abnormally high IOP can be damaging to your vision — again highlighting the importance for regular monitoring by an eye care provider.

A patient’s IOP can rise if the angle of the eye becomes clogged and the drainage becomes partially or fully blocked. As new fluid is created in the eye, the amount of fluid builds and the pressure increases. Overtime, an elevated IOP causes damage to the optic nerve, located in the back of the eye. Many types of glaucoma are characterized by damage to the optic nerve due to an elevated IOP. Read more about the different types of glaucomas and the warning signs here.

How is IOP measured?

During your annual eye exam, the eye doctor may use a variety of instruments to measure your IOP — this process is known as tonometry. These methods may include a puff of air onto the eye or a gentle tap on the eye with a probe. Learn more about what you expect at your eye exam here!

Eye health education is our passion! Click here to learn how Nanodropper is helping patients take control of their eye health.

Author: Alena Rainsberry

Medically reviewed by: Jordan Stanley, MD

Skip to content