What causes high eye pressure?
A look at ocular hypertension

Ocular hypertension is a condition that means your eye pressure is higher than the normal range — and though its symptoms aren’t always visible, it can lead to a variety of other problems. In particular, it’s a risk factor for a number of eye conditions — most common of which is glaucoma.

But what causes your eye pressure to rise, and how is it linked to glaucoma? Here, we’ll take a closer look at the causes of ocular hypertension, and at how it’s connected to glaucoma.

What is ocular hypertension?

Everyone has fluid within the front part of the eye (the anterior chamber). This fluid circulates in and out, bringing nutrients to the eye. It drains out through the angle between the iris (the coloured part of the eye) and the cornea (the clear front layer of the eye). Once it has passed through the angle it goes into the trabecular meshwork, a fine network of fibres that trap any debris in the fluid. For most people, fluid circulates in and out at the same rate, so the pressure in the eye remains constant (though the level of pressure inside your eye can vary from person to person, and one person’s eye pressure can naturally vary at different times of day).

In some people, the pressure can be higher than normal, which is known as ocular hypertension. This isn’t something that you can tell that you have — someone with ocular hypertension is usually not aware of any signs or symptoms. It won’t have any impact on your day to day life either, so the only way you can find out about the pressure inside your eye is by going for an eye test, where your eye pressure can be measured.

The impact of ocular hypertension: glaucoma

High eye pressure can cause pressure on the fine nerve fibres found at the back of the eye. This pressure can slowly damage them, and over time, lead to sight loss. This condition, where the nerve fibres are damaged, is known as glaucoma. It’s more likely to affect people aged 40 and over, runs in families, and is more common in people of African or Afro-Caribbean heritage.

While you won’t initially notice sight loss from high eye pressure, it can slowly affect your visual field, meaning that you might miss something at the edge of your vision. This can be dangerous when you’re out and about, and particularly when you’re driving. It’s very unlikely you would notice this sort of change to your vision in the early stages, but as well as checking the pressure in your eye, an optometrist can check your field of vision.

What to do if you have ocular hypertension

It’s important to have your eyes tested every two years (or more often if advised) — and people with a family history of glaucoma may be advised to have annual eye tests. The optometrist can track the pressure inside your eyes and your visual fields over time, which means that any small changes can be picked up early.

A particularly good way of assessing if the pressure in the eye is causing any issues is through OCT tests: a hospital-grade scan that allows the optometrist to see a 3D cross-section of the nerve fibres at the back of the eye.

Assessing both the visual fields and pressure, ideally along with assessing the nerve fibre layer using an OCT, is important because around 40% of people may have normal eye pressure, but there is still damage to the nerve fibres.

If any signs of abnormally high pressure, visual field loss and/or nerve fibre layer damage are picked up, you’ll be referred to the eye hospital to see a specialist eye doctor known as an ophthalmologist. They will examine your eyes and confirm if you have glaucoma, and from that point, there are a range of different treatments for glaucoma: including eye drops, surgery, and laser treatment.

The bottom line

We all have pressure inside our eyes, and for most people, this pressure is at a normal and healthy level. Some people can have relatively high pressure without it causing any problems — but for other people, high pressure can be a sign of glaucoma. The important thing is to have regular eye tests, so that your optometrist can make sure your eyes stay as healthy as possible.

If you’ve been having any problems with your eyesight, want to know more about your eye health, or find out about your risk of glaucoma, ask your local store about booking an OCT scan as part of your eye test.

Or for more information on glaucoma causes, you can find similar content in our dedicated glaucoma causes hub.

Josie Forte
DOptom BSc(Hons) MCOptom

Josie is an optometrist registered with the UK General Optical Council and New Zealand Board of Optometrists and Dispensing Opticians. She graduated from Cardiff… Read more