Glaucoma: What It Is, How It Is Detected, and What Happens Next

What is glaucoma?

Glaucoma is a group of eye conditions characterised by progressive damage to the optic nerve — the cable of 1.2 million nerve fibres that transmits visual information from the eye to the brain. In most cases, this damage is related to raised intraocular pressure (IOP), though some patients develop glaucoma with IOP in the normal range (normal tension glaucoma).

The most common type — chronic open-angle glaucoma (COAG) — develops slowly over years. Acute angle-closure glaucoma is a sudden, painful emergency (see our red eye article). Other types include normal tension glaucoma, pseudoexfoliative glaucoma, and pigment dispersion syndrome.

Risk factors

• Age — risk increases significantly after 60
• Family history — first-degree relative with glaucoma approximately doubles your risk
• Elevated intraocular pressure
• African-Caribbean ethnicity — higher prevalence and often earlier onset
• High myopia (short-sightedness)
• Long-term steroid use (eye drops, oral, or inhaled)
• Diabetes and hypertension

How is glaucoma detected?

Glaucoma is most commonly detected at a routine optician visit. The key tests are:

• Intraocular pressure measurement (tonometry) — a raised IOP is a risk factor but not diagnostic alone.
• Optic nerve assessment — examination and photographs of the optic disc to look for characteristic changes (cupping, notching, haemorrhages).
• Visual field test (perimetry) — a computerised test of the peripheral visual field. Loss of peripheral field is the hallmark of glaucoma damage.
• OCT (optical coherence tomography) — high-resolution imaging of the retinal nerve fibre layer, detecting thinning before visual field loss occurs.
• Pachymetry — corneal thickness measurement, as thin corneas give falsely low IOP readings.

Treatment

Glaucoma cannot be reversed — damage already done to the optic nerve is permanent. Treatment aims to lower IOP to prevent or slow further damage.

• Eye drops — the first-line treatment. Prostaglandin analogues (latanoprost, bimatoprost) are most commonly used. Drops must be used every day, indefinitely.
• Laser trabeculoplasty (SLT) — a laser procedure that improves drainage of fluid from the eye. Often recommended as a first-line treatment instead of drops. Effective in many patients for 3–5 years.
• Surgery (trabeculectomy / tube implant) — for glaucoma not controlled by drops or laser. Creates a new drainage route for intraocular fluid. Highly effective but requires careful post-operative monitoring.

NHS screening and optician referral

In the UK, anyone over 40 with a first-degree relative (parent, sibling, child) with glaucoma is entitled to free NHS sight tests. If your optician suspects glaucoma, they will refer you to an NHS or private ophthalmology clinic for a comprehensive glaucoma assessment.