Ocular hypertension

Ocular hypertension (OHT) happens when the pressure in your eye is higher than normal. High eye pressure is caused by a build-up of fluid in the eye that doesn't drain away properly.

Ocular hypertension doesn't cause noticeable symptoms and is a risk factor for glaucoma. That's why regular eye exams are essential, especially for anyone over the age of 40 or with a family history of glaucoma. An eye exam can detect high eye pressure, meaning you can start treatment to bring down your eye pressure and slow down or prevent the development of glaucoma.

Ocular hypertension symptoms

Most people with high intraocular pressure (IOP) don't have noticeable symptoms. Although some eye conditions can cause high pressure in the eye, ocular hypertension can occur in healthy eyes without any signs of eye disease.

Ocular hypertension is usually diagnosed at a routine optician appointment. Ocular hypertension is a risk factor for developing glaucoma, which is one reason why regular eye exams are so important. Research has found that roughly 10% of people with ocular hypertension are at risk of glaucoma after five years (Source: Ocular Hypertension Treatment Study). You won't know that you have high intraocular pressure, but diagnosis, monitoring, and treatment can prevent or slow its progression to glaucoma.

Ocular hypertension treatment

There are treatment options to manage ocular hypertension. These include medicated eye drops and, very occasionally, laser therapy. Both aim to lower intraocular pressure.

Not everyone diagnosed with ocular hypertension needs treatment if the pressure in the eye is not causing any signs of damage. Your optometrist or ophthalmologist will consider factors including how high the pressure is in your eye and whether you are at high risk of glaucoma, for example, due to age or family history of the disease. People with ocular hypertension are sometimes known in ophthalmology as 'glaucoma suspects' due to the risk of glaucoma.

Treatment aims to lower the elevated pressure in the eye to prevent glaucomatous damage that can lead to vision loss. If there are any signs of damage to your optic nerve as well as ocular hypertension, you'll need treatment.

The most common treatment for ocular hypertension is medicated eye drops. This is the same treatment as for glaucoma. The drops work by reducing the amount of aqueous fluid the eye produces or helping the fluid drain away.

You may use them first in one eye to check they are effective before using them in both eyes. Some people take more than one type of eyedrop. Tell your eye doctor if you experience side effects, as there may be alternatives that suit you better.

You should have regular follow up appointments to monitor your eye pressure, typically once every six months to a year.

Rarely, people need laser treatment (selective laser trabeculoplasty (SLT)). This is usually reserved for when the eye drops aren't working or can't be used or tolerated. This treatment aims to improve the drainage of fluid from the eye, which can reduce pressure.

What causes ocular hypertension?

Ocular hypertension is when the pressure in the eye, known as intraocular pressure, is higher than normal.

There is fluid in the eye called aqueous humour, which is continually produced and drained away through channels in the eye. This process maintains a normal pressure in the eye. When the drainage channels don't work properly, there's a build-up of fluid that increases pressure.

Eye pressure is measured in mmHg, with a pressure of 16mmHg being average and above 21mmHg being considered high. However some people can tolerate a higher eye pressure than others without any damage, and some may develop glaucoma with a lower than normal pressure (low tension glaucoma).

Some people are at increased risk of ocular hypertension, including those:

• With a family history of ocular hypertension or glaucoma
• Who have diabetes or high blood pressure
• With high myopia (very near-sighted)
• Aged 40 and older
• Who are African-American or Hispanic
• Who have previously had an eye injury or eye surgery
• Taking a long-term steroid medicine

Is ocular hypertension the same as glaucoma?

No, ocular hypertension isn't the same as glaucoma. Ocular hypertension is when you have high intraocular pressure but don't have signs of glaucoma such as optic nerve damage, visual field defects or visual field loss.

The most common type of glaucoma is primary open-angle glaucoma (POAG), and ocular hypertension puts you at a higher risk of developing this.

If high eye pressure isn't controlled, glaucoma can develop, especially if you have other risk factors. Risk factors that make glaucoma more likely in people with ocular hypertension include:

• Family history of glaucoma
• Having a thin central corneal thickness
• Older age
• Very high intraocular pressure
• Being very nearsighted (high myopia)

If you're at risk, find out more about glaucoma symptoms, glaucoma treatment, and living with glaucoma on the glaucoma page.

Getting an ocular hypertension diagnosis

An optometrist will check for high eye pressure and diagnose ocular hypertension. They’ll do a series of tests to examine your eyes and check for signs of any eye conditions that could cause ocular hypertension. The tests they do could include:

• A visual acuity test in which you read the letters on an eye chart.
• They'll examine the front of your eyes using a microscope called a slit lamp.
• They will use a tonometer to do a tonometry test to measure the pressure inside the eye.
• A check for signs of damage to the optic nerve, sometimes using eye drops to dilate your pupils.
• A gonioscopy test to check the eye’s drainage angle and other conditions that could cause high eye pressure.
• A visual field test to assess your side vision and check for any visual field defects due to glaucoma.
• They may also check your corneal thickness - a thinner cornea can give falsely low eye pressure readings or a thicker cornea can give falsely high measurements. 

Your optician will be looking for any signs of optic nerve damage or visual field changes that could indicate glaucoma rather than ocular hypertension alone.

When to get medical advice

The NHS recommends everyone should have eye tests at least every two years. With regular eye examinations, you're more likely to catch problems sooner, manage your eye health and get an early diagnosis and treatment for a range of eye diseases.