Why early diagnosis matters
Glaucoma is often asymptomatic and mainly affects older adults. It is diagnosed during a routine eye examination: age is an important risk factor, and only a specialist doctor can properly assess eye pressure and clinical signs.
The silent thief of sight
Glaucoma is called that because it can progress without obvious symptoms until the damage is already significant. Once the visual field is compromised, it cannot be recovered.
- General population
- A complete eye examination from the age of 40, then at the interval recommended by your ophthalmologist, becoming more frequent as you get older.
- People at high risk
- Family history, high myopia, diabetes, age over 60, use of corticosteroids, eye injury — more frequent check-ups, as advised by your ophthalmologist.
- Ethnic origin
- People of African origin have a higher risk of open-angle glaucoma, and people of East Asian origin a higher risk of angle-closure glaucoma.
- What is needed
- A full assessment including at least tonometry, fundus examination, visual field test and OCT.
The 6 main tests
Diagnosing glaucoma relies on a full assessment that combines six instrument-based tests. None of these on its own is enough to establish the diagnosis.
- 01
Tonometry
Eye pressureTonometry measures intraocular pressure (IOP). It is an essential test, but not enough on its own: many people with glaucoma have pressure within the normal range.
Three main techniques: Goldmann applanation tonometry (the gold standard, measuring the force needed to flatten the cornea), air-puff tonometry (non-contact, used in screening) and rebound tonometry (portable, useful in children).
Reference values
- 02
Gonioscopy
Drainage angleIt assesses the angle formed between the cornea and the iris, where the aqueous humour drainage system (the trabecular meshwork) is located. It helps distinguish between open-angle and angle-closure glaucoma.
How it is done: a special contact lens (a goniolens) is placed on the anaesthetised eye. The doctor uses a slit lamp to look at the angle and grade its width and any abnormalities.
- 03
Fundus examination
Assessing the optic nerveOphthalmoscopy allows the doctor to examine the optic nerve (optic disc) directly, looking for signs of glaucomatous damage. It is combined with stereoscopic photography of the optic disc and confocal laser ophthalmoscopy (HRT).
Signs of glaucoma at the optic disc
- 04
Visual field test
Computerised visual fieldIt maps the patient's peripheral and central vision, identifying areas of vision loss caused by glaucomatous damage. It is essential for monitoring how the disease progresses.
How it is done: the patient looks at a central point and presses a button each time they see a flashing light in their peripheral vision. The test takes 5-10 minutes per eye.
Typical defects in glaucoma: paracentral scotoma (close to the point of fixation), nasal step (along the horizontal meridian), concentric narrowing ('tunnel vision') and arcuate scotoma (following the nerve fibres).
Please note
Visual field defects do not appear until about 30-40% of the optic nerve fibres have been lost. Diagnosis must be based on several tests combined, not on the visual field alone.
- 05
OCT — Optical Coherence Tomography
3D imagingA high-resolution imaging technology that creates three-dimensional images of the structures of the eye, in particular the retinal nerve fibre layer (RNFL) and the optic disc. It is non-invasive and quick, with a resolution of up to 5 micrometres.
Parameters assessed: RNFL thickness around the optic disc, ganglion cell volume (GCC, macular thickness), optic disc analysis (area, cup volume, cup-to-disc ratio).
Early detection
OCT can detect loss of nerve fibres before visual field defects become apparent, allowing treatment to be started sooner. Essential for measuring progression over time.
- 06
Corneal pachymetry
Corneal thicknessIt measures corneal thickness. This matters because a thin or thick cornea can affect the measurement of intraocular pressure, and corneal thickness is an independent risk factor.
Reference values
Diagnostic criteria
Diagnosing glaucoma relies on a combination of several elements — not a single test, but an integrated clinical picture.
Established glaucoma
The diagnosis is based on the following combination of findings:
- Typical damage to the optic nerve (cupping, thinning of the nerve fibres)
- Visual field defects that match the damage to the optic nerve
- Intraocular pressure may be raised or within the normal range
Suspected glaucoma
When only some of these signs are present, regular check-ups are needed, at the interval set by your ophthalmologist:
- Raised intraocular pressure without obvious damage
- A suspicious-looking optic nerve without visual field defects
- A narrow angle without signs of closure
How often check-ups are needed
How often check-ups are needed depends on the stage of the disease and on how you respond to treatment. Your ophthalmologist tailors this to each case.
After diagnosis
European Glaucoma Society guidelines suggest around three visual field tests a year during the first two years, to measure how quickly the disease is progressing.
Stable glaucoma
Appointments, OCT and visual field tests at the intervals set by your ophthalmologist, based on the stage and risk.
Progressing glaucoma or a change in treatment
Closer check-ups until the target pressure is reached and the disease is stable.
After surgery
Frequent check-ups in the first few weeks, then gradually less frequent, as advised by the centre that operated on you.
Early diagnosis helps save sight
Glaucoma is a progressive and irreversible disease, but early diagnosis and prompt treatment can preserve sight for life in most patients. Do not wait for symptoms: glaucoma can progress silently.