TL;DR
If you’ve been told your eye pressure is raised, you may have come across both terms – ocular hypertension and glaucoma – and wondered whether they mean the same thing.
What is ocular hypertension?
Ocular hypertension (OHT) simply means that the pressure inside your eye is higher than normal. Eye pressure – known as intraocular pressure, or IOP – is determined by the balance of fluid production and drainage within the eye. When this fluid, called the aqueous humour, can’t drain properly, pressure builds up.
A normal IOP sits between 10 and 21 mmHg. Ocular hypertension is diagnosed when pressure exceeds 21 mmHg on two separate occasions, but there is no sign of damage to the optic nerve or any change to the visual field. In other words, the pressure is elevated, but the eye is otherwise healthy.
Around 1.3 million adults in the UK are estimated to have ocular hypertension – making it far more common than many people realise.
Crucially, most people with OHT have no symptoms at all. There’s no pain, no blurring, nothing to suggest anything is wrong. It’s almost always picked up during a routine eye test.
What is glaucoma?
Glaucoma is a group of eye conditions in which the optic nerve becomes damaged – typically, though not always, as a result of raised intraocular pressure. Unlike ocular hypertension, glaucoma involves actual structural damage, and that damage can lead to permanent vision loss if left untreated.
The most common form in the UK is primary open-angle glaucoma, which develops slowly and silently over many years. Peripheral vision is usually the first to be affected, which is why so many people don’t notice anything until the condition is already fairly advanced. You can read more about how and when it tends to develop in our piece on age and glaucoma onset.
So, what’s the key difference between ocular hypertension and glaucoma?
The clearest way to think about it is this: ocular hypertension means a raised pressure within the eye, although the eye is otherwise healthy. In glaucoma, there is usually high pressure alongside a damaged optic nerve and visual field loss.
Raised eye pressure is a major risk factor for glaucoma – but it is not glaucoma itself. Many people live with elevated eye pressure for years without ever developing the condition. Equally, it’s possible to develop glaucoma with normal eye pressure, a form known as normal-tension glaucoma.
The crossover point – where OHT becomes glaucoma – is when optic nerve damage or visual field changes are detected. Until that point, a diagnosis of ocular hypertension is used.
Does ocular hypertension always lead to glaucoma?
No. Ocular hypertension affects 3–5% of the population over 40, but only a small proportion of these people go on to develop glaucoma. That said, the risk is real and increases over time, which is why monitoring is so important.
Several factors influence how likely it is that OHT will progress to glaucoma, including:
- The level of eye pressure – the higher it is, the greater the risk.
- Central corneal thickness – a thinner cornea can indicate greater vulnerability to pressure-related damage.
- Age – risk rises as you get older.
- Family history – having a close relative with glaucoma increases your chances significantly. If you’re wondering whether glaucoma runs in families, the short answer is yes, it can.
- Ethnicity – people of African, Caribbean, and Asian heritage are at higher risk.
How is ocular hypertension managed?
Not everyone with OHT needs treatment, but everyone with it needs monitoring. Regular eye examinations allow your optometrist or ophthalmologist to track any changes in optic nerve appearance and visual field – catching any signs of glaucoma at the earliest possible stage, when treatment is most effective.
Where treatment is recommended – typically when IOP is 24 mmHg or above and other risk factors are present – the first-line option is usually pressure-lowering eye drops, most commonly a prostaglandin analogue. These work by improving the drainage of fluid from the eye and are taken once daily.
In the UK, current guidance recommends treatment with eye drops if the eye pressure is greater than 24 mmHg, taking into account the individual’s overall risk profile.
What does this mean in practice?
If you’ve been diagnosed with ocular hypertension, try not to panic. It doesn’t mean you have glaucoma, and it doesn’t mean you’ll definitely get it. What it does mean is that your eyes need to be watched – consistently and carefully.
Attend your monitoring appointments, report any changes in your vision promptly, and make sure your optometrist is aware of any relevant family history. The earlier any progression is spotted, the better the outcome.
Good general eye health habits matter too. Staying active, not smoking, and eating a diet rich in antioxidants and eye-protective nutrients can all support long-term optic nerve health alongside any prescribed treatment.
The information in this article is intended for general guidance only and does not replace advice from a qualified eye care professional. If you have concerns about your eye pressure or vision, please contact your optometrist or GP.
