The short answerNormal eye pressure for most people is roughly 10 to 21 mmHg. But the number alone does not tell you whether the eye is healthy. Some people have pressure above 21 without any damage to the optic nerve, while others develop glaucoma with pressure in the normal range. That is why diagnosing glaucoma needs an examination and scan of the optic nerve and a visual field test, not just a pressure reading.
What is eye pressure?
The front of the eye contains a clear fluid that is made constantly and drains out through an angle between the cornea and the iris. The balance between how much fluid is made and how much drains away sets the eye pressure. If drainage slows, the pressure rises. Eye pressure is not the same as blood pressure, and it varies naturally by a few points through the day and between readings, so a doctor may need more than one measurement before deciding anything.
What does an eye pressure reading mean?
| Reading (mmHg) | Usual meaning | What happens next |
|---|---|---|
| Below 10 | Lower than usual, and can be normal for some people | Assessed by the doctor, especially after eye surgery or injury |
| 10 to 21 | The normal range for most people | Does not rule out glaucoma on its own, so a nerve check still matters for people with risk factors |
| About 22 to 30 | Higher than usual | Optic nerve exam, corneal thickness and visual field to tell high pressure alone from glaucoma |
| Above 30 | High | Needs prompt assessment, and treatment to lower it is often advised even before damage appears |
| Very high with pain, redness and blurred vision | Possible acute glaucoma attack | Emergency, the same day |
Does high pressure mean glaucoma?
Not necessarily. Glaucoma is damage to the optic nerve. High pressure is its most important risk factor, but it is not the disease itself. Someone with higher than normal pressure, a healthy nerve and a normal visual field is diagnosed with ocular hypertension. Their chance of developing glaucoma is higher than average, so they need regular checks, and some are treated preventively depending on their level of risk.
On the other side, there is normal-tension glaucoma: optic nerve damage with pressure readings in the normal range. This is why a normal pressure reading alone is not reassurance, especially for people with risk factors.
How is eye pressure measured?
- Air puff: a machine sends a gentle puff of air at the eye without touching it. It is quick and good for screening, but readings can vary.
- Goldmann applanation: measured at the slit lamp after numbing drops and a dye, with a light touch on the cornea. It is the reference standard in clinics.
- Other handheld devices: used for children or when examining at the slit lamp is difficult.
Corneal thickness affects the reading. A thick cornea can give a reading higher than the true pressure, and a thin one can give a lower reading. Because laser vision correction thins the cornea, pressure readings afterwards can be lower than the real value, so always tell your doctor if you have had laser surgery. This is why doctors measure corneal thickness when assessing eye pressure.
Diagnosing glaucoma needs more than a pressure check
- Examining the optic nerve at the back of the eye, usually after dilating drops.
- An OCT scan of the nerve and its fibre layer, to find early damage and measure change over time.
- A visual field test, because glaucoma starts with side vision that patients do not notice.
- Checking the drainage angle with a special lens, to see whether it is open or narrow.
- Measuring corneal thickness.
Who should have their eye pressure checked regularly?
- Everyone over 40, as part of a routine eye exam.
- Anyone with a parent, brother or sister who has glaucoma.
- People with high short-sightedness.
- People with diabetes.
- Anyone using steroids long term, whether drops, tablets, inhalers or creams around the eyes.
- Anyone who has had a serious eye injury in the past.
How often you need checks depends on your age, your risk factors and your previous results, and your doctor will advise.
Acute glaucoma attack: an emergency
In a type called angle-closure glaucoma, the drainage angle can close suddenly and the pressure rises very quickly. The signs are:
- Severe eye pain.
- A red eye.
- Blurred or suddenly reduced vision.
- Coloured halos around lights.
- Headache, sometimes with nausea or vomiting.
These symptoms need emergency eye care the same day and cannot wait until morning, because delay can cause permanent loss of vision.
Frequently asked questions
My eye pressure is 22. Do I have glaucoma?
Not necessarily. A reading of 22 is slightly above usual and may be due to a thick cornea or normal variation between readings. It needs an optic nerve exam, corneal thickness and a visual field test before any diagnosis.
Is eye pressure related to blood pressure?
They are different things. High blood pressure does not mean high eye pressure, and blood pressure medicines do not treat eye pressure. Tell your eye doctor about all your conditions and medicines.
How often should eye pressure be checked?
After 40 it is usually measured as part of a routine eye exam. People with a family history, diabetes, high short-sightedness or long-term steroid use may need more frequent checks, as their doctor advises.
Is the air puff eye pressure test accurate?
It is fine for screening, but readings can vary. If the result is high or borderline, the doctor repeats it with Goldmann applanation and measures corneal thickness.