What causes high eye pressure?

Ocular hypertension symptoms

Usually, you won’t experience any symptoms with ocular hypertension and it’s unlikely that it will cause any damage to your vision in the short term. However, the risks of developing glaucoma are much greater in the long term, which poses a risk to your sight.

What causes ocular hypertension?

The fluid within the front section of the eye is called aqueous humour, which supplies nutrients as well as taking away any waste. The level of eye pressure (intraocular pressure) is controlled by a balance between the amount of this fluid produced, and its drainage out of the eye.

Most cases of ocular hypertension are caused by a restriction or blockage in the eye’s drainage channels. Without proper drainage, the pressure of the fluid becomes greater than normal, causing higher eye pressure.

How does ocular hypertension link to glaucoma?

Consistently high pressure on the eyes is the most significant risk factor in the development of glaucoma – the higher the pressure, the greater the risk.

However, the relationship between eye pressure and glaucoma is complex and one which we don’t fully understand. While some people with ocular hypertension are more prone to developing glaucoma, the majority are not.

That’s why it’s important for your optician to keep an eye on your pressure so if higher levels are found, further tests can be arranged to assess whether you may be more or less prone to developing glaucoma.

High blood pressure in eyes

Untreated high blood pressure, also known as hypertension, can lead to a range of eye diseases. One of the conditions it can cause, for example, is hypertensive retinopathy, where the tiny arteries that supply blood to the retina are damaged.

If blood pressure is not controlled, this can lead to more serious eye damage, including bleeding, blurred vision, and complete loss of vision.¹

High blood pressure may also lead to the build-up of fluid under the retina, which can cause choroidopathy, a condition that can lead to distortion of vision or impaired vision due to scarring in the eye.¹

Hypertension may also block blood flow and cause damage to the optic nerve. This is known as optic neuropathy and can result in the death of nerve cells in the eye, leading to bleeding within the eye or vision loss.¹

High blood pressure and glaucoma: is there a link?

One particular condition that has been linked to high blood pressure is glaucoma, in which fluid builds up in the front part of the eye. This excess fluid increases the pressure in the eye, which damages the optic nerve, leading to progressive loss of vision.

Blood pressure and glaucoma share a complex relationship. Very high blood pressure can lead to an increase in intraocular pressure (pressure inside the eye), which is one of the main causes of glaucoma.

Low blood pressure is also not desirable, as it can lead to insufficient blood supply to the optic nerve.² This is an important consideration because over-treatment of hypertension with medications can lead to a situation where the blood pressure is too low and can cause damage to the eye. The key is to avoid extremes of blood pressure and to let your optometrist or ophthalmologist know if you’re taking any antihypertensive medications.

Risk factors of ocular hypertension

Anyone can develop ocular hypertension, but there are several factors that could increase the risk of getting the condition:

A family history of ocular hypertension or glaucoma
Age – chances are greater as we get older
Ethnicity – you’re more likely to develop this condition if you are from African-Caribbean descent
Very high myopia (short-sightedness)
Certain medications have side effects that raise eye pressure in some people
Eye injuries, even years after they happen, can affect your intraocular pressure

Finding ocular hypertension

During an eye test, your optician will perform tests in order to check for ocular hypertension and any signs of glaucoma:

Your eye pressure will be measured using a tonometer. For a normal, average eye pressure, they’ll be looking for a reading between 10mmHg and 21mmHG. Anything that is consistently above this level would indicate ocular hypertension.
The health of your optic nerve.
A visual field test will check your peripheral vision, where glaucoma begins.
Signs of other eye conditions that are related to increased eye pressure.

Treatments for ocular hypertension

Fortunately, ocular hypertension can be treated if necessary. The most common treatment is the use of eye drops to help reduce the eye pressure.

For the vast majority of people, ocular hypertension will not cause any problems, but around 10% will develop glaucoma over time. For those with a higher chance of developing glaucoma, daily eye drops can be prescribed to reduce the eye pressure and halve the risk of glaucoma occurring.

It’s important that you have regular eye tests so that we can monitor your eye pressure and look for the signs of glaucoma starting to develop. Treatment for glaucoma is most effective when it is caught early.

Did you know?

Ocular hypertension is detected during an eye test – so it’s important to have one regularly so that we can monitor your eye pressure, and any changes, over time.

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References

Mayo Clinic (no date). High blood pressure dangers: Hypertension’s effects on your body [Online]. Available at: https://www.mayoclinic.org/dis... [Accessed 17 May 2019].
He, Z., et al. (2011). The role of blood pressure in glaucoma. Clinical and Experimental Optometry, 94(133-149). [Online]. Available at: https://onlinelibrary.wiley.co... [Accessed 17 May 2019].