What Is Glaucoma, and Can You Prevent It?

Glaucoma is one of the leading causes of blindness worldwide. By the time most people notice anything is wrong, the condition has often been quietly doing damage for years. Understanding what glaucoma is and why catching it early matters so much. Could genuinely make the difference between preserving your vision and losing it.

Glaucoma is not a single condition, but a group of eye diseases that all cause damage to the optic nerve. That nerve is the cable that carries everything your eye sees back to your brain for processing. When the optic nerve is damaged, vision is permanently lost.

Inside a healthy eye, a clear fluid called aqueous humour is constantly being produced and drained. This cycle maintains a stable internal pressure, typically somewhere between 10 and 21 mmHg. Problems arise when that drainage system becomes sluggish or blocked. Fluid builds up, pressure rises, and the optic nerve begins to suffer.

Glaucoma is particularly dangerous because it usually affects side (peripheral) vision first. Most people do not notice any symptoms until permanent vision damage has already occurred. It is estimated that around half of people with glaucoma do not realise they have it.

Open-angle glaucoma is by far the most common form in the UK. The drainage angle in the eye remains open, but the drainage itself becomes gradually less efficient over time. A slow, process occurring over many years with no pain and no obvious symptoms. It affects roughly one in 50 adults over 40, rising to around one in ten among those over 75.

Acute angle-closure glaucoma is far rarer but considerably more dramatic. The drainage pathway closes suddenly. This causes a rapid spike in eye pressure that can produce intense eye pain, blurred vision, nausea, and halos around lights. This is a medical emergency requiring same-day treatment.

Normal-tension glaucoma is a variation in which the optic nerve is damaged despite intraocular pressure sitting within the normal range. A reminder that eye pressure alone does not give the full picture with glaucoma.

Several factors are known to raise the risk of developing glaucoma.

Age, risk increases notably from 40 onwards

Family history, having a first-degree relative with glaucoma raises your own risk significantly, and entitles you to a free NHS eye test

Ethnicity, people of African-Caribbean heritage have approximately four times the risk of open-angle glaucoma compared to those of European descent; people of East Asian heritage face a higher risk of angle-closure glaucoma

Raised eye pressure (ocular hypertension), not the same as glaucoma, but a recognised precursor

Short-sightedness (myopia), associated with increased susceptibility to open-angle glaucoma

Diabetes and high blood pressure, both linked to higher risk

Long-term use of corticosteroid medications

For most people, glaucoma itself cannot be prevented. The way the drainage system slows, or the optic nerve's inherent vulnerability are not things we can directly control. What can be managed is the risk of serious vision loss from it.

Early detection is the closest thing to prevention that currently exists. When glaucoma is identified before significant optic nerve damage has occurred, treatment can halt or dramatically slow its progression. Most people who receive a timely diagnosis retain useful vision for life. The challenge is that glaucoma gives you almost no help in detecting it yourself.

This is why regular eye tests are so important. A routine eye test includes checks that can identify raised pressure, assess the optic nerve's appearance, and test peripheral vision. Three of the key indicators of glaucoma.

Adults are advised to have their eyes tested at least every two years. Those with risk factors should discuss more frequent testing with their optometrist.

In England, you are entitled to a free NHS sight test if you are:

• Aged 60 or over
• Diagnosed with diabetes or glaucoma
• Considered at risk of glaucoma (including those with a family history in a first-degree relative)
• Aged 40 or over with a parent, sibling or child who has been diagnosed with glaucoma

If you're not sure whether you qualify, your optometrist can advise at your next visit.

While vision already lost to glaucoma cannot be recovered, treatment can be highly effective at preventing further damage. The goal in every case is to reduce intraocular pressure to a level at which the optic nerve is no longer at risk.

Medicated eye drops are the most common starting point. Most work either by reducing how much fluid the eye produces, or by improving how efficiently it drains. Many people manage their glaucoma with daily drops alone. Attending appointments every six to twelve months to ensure the treatment remains effective.

Where drops prove insufficient, laser treatment offers a less invasive option. Selective laser trabeculoplasty (SLT) improves drainage through the trabecular meshwork and is now offered as a first-line treatment for some patients.

For more advanced cases, surgical procedures such as trabeculectomy, which creates a new drainage channel, or minimally invasive glaucoma surgery (MIGS) can achieve lasting reductions in pressure.

NHS, glaucoma
Moorfields Eye Hospital NHS, glaucoma Overview
RNIB, understanding Glaucoma
Glaucoma UK, patient Information and Support

Royal College of Ophthalmologists, glaucoma Guidelines

Cleveland Clinic, glaucoma: Causes, Types & Treatment

Johns Hopkins Medicine, glaucoma

PMC / NCBI, updates on the Diagnosis and Management of Glaucoma (2022)

NICE, glaucoma: Diagnosis and Management (NG81)