Intraocular pressure, or eye pressure, is pressure from fluid inside the eye. Measuring intraocular pressure is important as high intraocular pressure can increase the risk of glaucoma.
The eye constantly produces a fluid called aqueous humour. It is present mostly at the front of the eye. The fluid drains away from the eyeball through small tubes, but the pressure can increase if the fluid is not able to properly drain.
Eye pressure naturally fluctuates throughout the day. However, it is important for eye doctors to regularly measure intraocular pressure to help monitor for risk factors for glaucoma.
Read on to learn more about intraocular pressure, including how and why doctors measure it, risk factors for elevated intraocular pressure, treatments, and more.
Eye doctors can measure intraocular pressure
GAT involves placing numbing drops into the eyes to make sure the test does not cause discomfort. The eye doctor will then use a slit lamp to look at your eyes and gently touch the surface of your eyes. This allows them to flatten a small area of the corneas to measure how much force is necessary to flatten the corneas.
Other ways to measure intraocular pressure include:
- Non-contact tonometry: Non-contact tonometry, or air-puff tonometry, uses puffs of air to flatten the corneas.
- Rebound tonometry: Rebound tonometry involves placing a small probe against the cornea. By moving it slightly, the eye doctor can measure how your eye responds to the touch of the probe.
- Tonometer pen: A tonometer pen, or tonopen, is a portable device. The eye doctor will use numbing drops on the eyes, and then they will use the tonopen to touch the cornea and measure the indentation.
It is important to measure intraocular pressure as ocular hypertension, where the eye pressure is higher than usual, is a risk factor for glaucoma.
Ocular hypertension typically refers to intraocular pressure of greater than
Not everybody with intraocular pressure of greater than 21 mmHg will develop glaucoma.
Although uncommon, you may also experience ocular hypotony. This is typically when the eye pressure is under 7 mm Hg. Possible causes of ocular hypotony include:
- chronic eye inflammation
- detachment of the retina
- post-surgical wound leak, such as after trabeculectomy for glaucoma
Treatment for high or low intraocular pressure will depend on the cause.
Intraocular pressure can change throughout the day. It typically ranges from 10 mmHg to 21 mmHg.
It can vary as much as 6 mmHg. It is typically higher first thing in the morning, though not always.
Eye pressure is more likely to fluctuate throughout the day in individuals with glaucoma.
Risk factors for elevated intraocular pressure or ocular hypertension include:
- being over the age of 40 years
- having myopia (nearsightedness) or hyperopia (farsightedness)
- a family history of glaucoma or ocular hypertension
- high blood pressure
- diabetes
- surgery or injury to the eye
- previous use of eye injections
- pigment dispersion syndrome, a condition affecting the pigment at the back of the iris
- pseudoexfoliation syndrome, a condition causing protein-like materials to build up in the eye
- long-term use of steroid medications
Treatment may not always be necessary for high intraocular pressure. Your eye doctor will assess your risk of developing glaucoma, and will typically recommend treatments if there is a moderate to high risk of glaucoma.
Eye drops can help lower intraocular pressure by 20% to 25%. Types that can help include:
- beta-blockers
- prostaglandins
- alpha agonists
- carbonic anhydrase inhibitors
- the rho-kinase inhibitor netarsudil
Rarely, your doctor may recommend laser surgery to treat high intraocular pressure.
If the risk of glaucoma is low, your doctor will likely monitor your eye pressure.
Your doctor may measure your intraocular pressure as part of your routine eye exam. If they detect high intraocular pressure but a low risk of glaucoma, they may recommend more frequent monitoring.
If there is high intraocular pressure and a high risk of glaucoma, they may recommend tests every 6 to 12 months.
Intraocular pressure, or eye pressure, refers to the buildup of aqueous humour that can happen if the fluid cannot drain properly from the eye.
Typical intraocular pressure is from 10 mmHg to 21 mmHg. If the measurement is higher than this, it usually indicates ocular hypertension, which is a risk factor for glaucoma.
If intraocular pressure is below 7 mmHg, this is ocular hypotony. This is less common than ocular hypertension, and can occur following eye injury or surgery, chronic eye inflammation, or retinal detachment.
Getting regular eye tests can help your eye doctor identify changes in intraocular pressure. If there is a moderate to high risk of glaucoma, they may recommend more frequent testing, as well as eye drops to lower intraocular pressure.