TL;DR
A glaucoma test usually takes between 30 and 60 minutes in total, but the individual checks that make up that appointment are quick and painless. Here’s everything you need to know.
What happens during a glaucoma test?
A glaucoma assessment isn’t a single test. It’s a series of checks that together give your optometrist or ophthalmologist a full picture of your eye health. Each test focuses on a different part of the eye, and most take just a few minutes each.
Eye pressure measurement (tonometry)
This is often the first check and the one most people associate with glaucoma testing. Your optometrist measures the pressure inside your eye – known as intraocular pressure (IOP). Raised IOP is one of the main risk factors for glaucoma.
The most common method used in UK clinics is noncontact tonometry (the “air puff” test), which takes only seconds per eye. A more precise version, Goldmann applanation tonometry, may be used in hospital settings and involves a gentle probe touching the surface of the numbed eye.
Time taken: 2–5 minutes
Visual field test (perimetry)
This test checks your peripheral vision, which is often the first area affected by glaucoma. You’ll sit in front of a screen and press a button each time you see a flashing light. The test maps out any blind spots in your vision.
It can feel a little repetitive, but it’s completely painless. According to Glaucoma UK, this is one of the most important tools for detecting and monitoring the condition.
Time taken: 10-15 minutes
Optic nerve examination
Your optometrist will examine the back of your eye to look at the optic nerve directly. Eye drops are usually applied first to dilate (widen) your pupils, which makes the nerve easier to see. This is where signs of glaucoma damage – such as thinning or cupping of the nerve – can be spotted.
Note that dilating drops may temporarily blur your vision and make your eyes sensitive to light, so it’s worth bringing sunglasses and arranging a lift if possible.
Time taken: 5–10 minutes (plus 20–30 minutes waiting for drops to work)
Corneal thickness measurement (pachymetry)
Corneal thickness affects how eye pressure readings are interpreted – a thinner cornea can cause IOP to appear lower than it actually is. This test uses a small probe or ultrasound device to measure the thickness of the cornea.
Time taken: 2–5 minutes
OCT scan (optical coherence tomography)
Many UK clinics now use OCT scanning as part of a glaucoma assessment. This technology creates detailed cross-sectional images of the optic nerve and the retinal nerve fibre layer, allowing clinicians to detect subtle structural changes – sometimes before any vision loss has occurred.
Time taken: 5–10 minutes
So, how long does the whole appointment take?
Putting it all together, here’s a rough guide:
- Routine glaucoma screening (e.g. as part of a standard NHS eye test): 15–30 minutes
- Full glaucoma assessment at a hospital clinic: 45–90 minutes
- Followup monitoring appointment: 30–60 minutes
The extra time at a hospital appointment is largely due to waiting for dilating drops to take effect, as well as the more comprehensive range of tests carried out.
If you’ve been asked to attend a glaucoma clinic for the first time, it’s sensible to allow at least 90 minutes for your visit – including time in the waiting room.
Who gets tested for glaucoma in the UK?
In the UK, the NHS offers free eye tests to people who are at higher risk of glaucoma. You qualify for a free test if you:
- Are aged 40 or over and have a close family member with glaucoma
- Have been diagnosed with glaucoma or ocular hypertension
- Are referred by a GP or hospital consultant
You can read more about at what age glaucoma tends to develop in our dedicated guide, which also covers risk factors and early detection.
Related read: Is Glaucoma Genetic?
Is a glaucoma test painful?
No – glaucoma tests are not painful. Some people find the air puff test slightly startling, and the dilating eye drops can cause temporary stinging, but neither is uncomfortable for more than a moment.
The visual field test requires concentration and can feel tiring, particularly if your appointment is long. It’s perfectly normal to feel like you’ve missed some flashes – the test is designed to be challenging, and results are interpreted alongside your other findings.
What happens after the test?
Results from a glaucoma assessment are reviewed by an ophthalmologist or specialist optometrist. Depending on the findings, you may be:
- Discharged – your eyes are healthy and no further action is needed
- Monitored – you’ll be asked to return for followup appointments to track any changes
- Referred for treatment – if glaucoma is confirmed, treatment (usually eye drops) will be recommended promptly
Glaucoma cannot be reversed, but when caught early it can be managed effectively to preserve your vision. That’s why regular eye tests are so important, even if you have no noticeable symptoms. You can learn more about gradual vision loss and what to look out for on our blog.
The key takeaways
A glaucoma test is straightforward, painfree, and usually takes under an hour. It involves several quick checks that together build a detailed picture of your eye health. If you’ve been invited for a test – or you’re overdue an eye check – don’t put it off.
Early detection is the single most effective way to protect your sight.
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 vision, please contact your optometrist or GP.
