Eye pressure

The pressure inside your eye must remain within normal parameters for optimal eye health. Eye pressure that is too high or too low can impact vision and cause ocular symptoms. Abnormal eye pressure can sometimes signify other eye problems.

Here, we’ll talk about the normal eye pressure range and the causes, symptoms and treatments of abnormal eye pressures.

What is pressure inside the eye?

The medical name for eye pressure is intraocular pressure (IOP). Normal eye pressure should be between 10mmHg and 21mmHg (Source: National Library of Medicine). High intraocular pressure often comes from a build-up of fluid due to a problem with fluid production and drainage in the eye. Other causes of raised eye pressure include trauma, inflammation or certain medications.

Normal eye pressure

Eye pressure is measured in millimetres of mercury (mmHg). Eye pressure fluctuates in individuals. These fluctuations can be harmless and go undetected, or they can signify eye problems. The normal range is 10-21mmHg.

Symptoms of high eye pressure

If the pressure inside the eye increases slowly over time, it does not cause any feeling of pressure or tension, even though the raised pressure can eventually lead to sight loss. However, a sudden rise in pressure will cause pain and discomfort. An optometrist may detect high pressure during an eye examination, so regular check-ups are essential to rule out glaucoma or other causes of high pressure.

Other eye pressure symptoms include:

Eye pressure test

Your optometrist may perform a tonometry test to measure your eye pressure. During the test, they will administer numbing eye drops and then use a tonometer to measure the resistance of your eye’s surface. Another type of test involves blowing a small puff of air onto the eye’s cornea. Measuring corneal thickness can also help determine your risk of developing raised intraocular pressure.

What causes high eye pressure?

Glaucoma and high eye pressure are closely linked. In ophthalmology, anyone with raised intraocular pressure is known as a glaucoma suspect. In glaucoma, the fluid in the eye (aqueous humour) builds up due to a problem with its drainage system. The drainage channels (trabecular meshwork) can get blocked, and fluid gets trapped in the eye. The increased IOP can cause optic nerve damage and vision loss. The most common type of glaucoma is primary open-angle glaucoma. It is also possible to develop glaucoma with normal eye pressures, called normal-tension glaucoma.

Treatment of high eye pressure

In most cases, your doctor or ophthalmologist can treat high eye pressure if it is detected before complications arise. Regular tonometry tests can help your optometrist monitor your eye pressure.

Some of the possible treatments to lower eye pressure include:

Ocular hypertension

Ocular hypertension is a condition in which the eye pressure is higher than normal (over 21mmHg) but is not associated with any damage to the optic nerve or vision loss. However, it is a risk factor for developing glaucoma and so may require monitoring by an optometrist.

Glaucoma

Glaucoma is an eye disease where fluid builds up in the eye, causing increased eye pressure and damage to the optic nerve. There are different types of glaucoma; the most common is primary open-angle glaucoma. Treatments for glaucoma include eye drops, laser therapy and surgery. Glaucoma left untreated can lead to vision loss.

Frequently asked questions

Eye pressure above 21mmHg is considered high and requires assessment and monitoring from your optometrist or eye doctor. Eye pressure of 40-50mmHg or above is particularly dangerous and can occlude the veins and cause accelerated vision loss (Source: BMJ). Individuals with weaker optic nerves may experience eye damage at lower pressures.

Conclusion

High eye pressure can be a sign of a serious eye condition that can damage the eyes and cause vision loss. If you have a family history of glaucoma or are worried that your eye pressure may be raised, see an optician or eye doctor for an assessment and advice on eye care.

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Medically reviewed by: The Royal College of Ophthalmologists on 06/09/2022

Edited by: Nick Astbury FRCS FRCOphth FRCP
Clinical Associate Professor
LSHTM

The Royal College of Ophthalmologists champions excellence in the practice of ophthalmology and is the only professional membership body for medically qualified ophthalmologists. The RCOphth is unable to offer direct advice to patients. If you’re concerned about the health of your eyes, you should seek medical advice from your GP, optometrist or ophthalmologist.