Intraocular Pressure: What It Is, Why It Matters & How to Keep It Healthy

If you’ve ever heard doctors talk about "eye pressure" and wondered what it really means, you’re not alone. Intraocular pressure (IOP) is the fluid pressure inside the eye. It’s a simple number, but it tells a lot about your eye’s health and can signal serious problems early on.

How Intraocular Pressure Is Measured

Eye doctors use a device called a tonometer to get the IOP reading. The most common method is a quick puff of air that flattens the cornea for a split second. The machine translates that flattening into a pressure value, usually reported in millimeters of mercury (mmHg). The whole process takes less than a minute and doesn’t usually hurt.

Normal IOP ranges from about 10 to 21 mmHg. Anything consistently above 21 mmHg is considered high, while readings below 10 mmHg are low. Both extremes can cause problems, so regular checks are key, especially if you have risk factors.

Why High or Low IOP Matters

High IOP is the biggest risk factor for glaucoma, a disease that silently damages the optic nerve and can lead to vision loss. Even if you feel fine, persistent high pressure can erode peripheral vision over years. Low IOP, on the other hand, can be a sign of eye injury, inflammation, or certain surgeries. It can also cause blurry vision and eye discomfort.

Both conditions are manageable when caught early. Your doctor may suggest eye drops, laser therapy, or surgery to bring the pressure back into the safe zone. Lifestyle tweaks—like staying hydrated, exercising regularly, and avoiding excessive caffeine—can also help.

Speaking of lifestyle, a few everyday habits can keep IOP steady. Regular aerobic exercise, such as brisk walking or cycling, improves blood flow to the eye and often lowers pressure. Eating foods rich in antioxidants—leafy greens, berries, and fish—supports overall eye health. If you wear steroids, whether topical or oral, ask your doctor about the impact on eye pressure.

People with a family history of glaucoma should get their eyes checked at least once every two years, even if they feel fine. Diabetes, high blood pressure, and being over 60 also raise the odds of developing pressure problems.

When you receive an IOP reading, don’t panic if it’s a bit out of range. One number doesn’t define your eye health. Your doctor will look at the whole picture—cornea thickness, optic nerve health, and visual field tests—to decide if treatment is needed.

Bottom line: intraocular pressure is a simple but powerful gauge of eye health. Regular check‑ups, a balanced diet, and staying active keep the numbers in check and protect your vision for the long run.