# Glaucoma: symptoms, causes and treatment > Source: World Aid Network — https://worldaidnetwork.org/eye-health/glaucoma > Last reviewed: 2026-06-19 ## In short Glaucoma is a group of eye conditions that damage the optic nerve, the cable that carries pictures from the eye to the brain. It is usually linked to a build-up of pressure inside the eye. Its danger is its silence: the most common type causes no pain and no early symptoms, quietly stealing side vision first, so many people do not notice until sight is permanently lost. The good news is that a routine eye test can detect it early, and treatment — usually simple daily eye drops — can stop it getting worse. Sight already lost cannot be recovered, which is why regular eye tests are the single best protection. Glaucoma is a group of eye conditions in which damage to the optic nerve causes progressive, irreversible loss of vision. It is the second leading cause of blindness in the world after cataracts, affecting an estimated 80 million people globally. Around 700,000 people in the UK have glaucoma — but up to half are undiagnosed because the most common type causes no symptoms until significant, permanent vision loss has already occurred. This is why glaucoma is often called the 'silent thief of sight'. By the time most people notice their vision is affected, they have already lost a significant portion of their visual field — damage that cannot be restored. The only way to detect glaucoma early is through regular eye examinations. This guide answers the twenty most commonly searched questions about glaucoma in the UK, drawing on NHS and WHO sources. ## At a glance - Nickname: Silent thief of sight - Early symptoms: Usually none - Detected by: A routine eye test - Main treatment: Daily eye drops ## When to see a doctor - Most chronic glaucoma has NO early symptoms — the key action is regular eye tests - Patchy blind spots in your side (peripheral) vision - Blurred vision or trouble adjusting between light and dark - URGENT: sudden severe eye pain, headache, nausea, redness and haloes around lights — this can be acute glaucoma; seek emergency eye care immediately ## Types of glaucoma Primary open-angle glaucoma (POAG) is by far the most common type, accounting for approximately 90% of cases in the UK. It develops slowly and painlessly as the drainage channels within the eye become gradually less efficient, causing intraocular pressure (IOP) to rise and optic nerve damage to accumulate over years. Peripheral vision is lost first, followed progressively by central vision if untreated. Acute angle-closure glaucoma is a medical emergency in which the drainage angle of the eye suddenly closes, causing a rapid and severe rise in eye pressure. It presents with sudden, severe eye pain, nausea, vomiting, blurred vision, headache and seeing haloes around lights. This requires urgent hospital treatment. Normal tension glaucoma is a variant in which optic nerve damage occurs despite intraocular pressure within the statistically normal range. Secondary glaucoma arises as a consequence of another eye condition or systemic disease. ## Diagnosis and NHS eye tests Glaucoma is detected through a comprehensive eye examination that includes: tonometry (measurement of intraocular pressure); optic disc assessment (looking for characteristic glaucomatous cupping and pallor); visual field testing (to detect areas of peripheral vision loss); and optical coherence tomography (OCT) — an imaging scan that measures the thickness of the retinal nerve fibre layer and detects early glaucomatous damage before visual field loss becomes apparent. The NHS provides free eye tests for people at increased risk of glaucoma: those aged 40 and over with a first-degree relative (parent, sibling or child) with glaucoma; anyone over 60; people of black African or Caribbean heritage aged 40 and over; and anyone referred by their optician or GP with suspected glaucoma. The NHS recommends everyone has a routine eye test at least every two years. ## Treatment options Glaucoma treatment aims to lower intraocular pressure to protect the optic nerve from further damage — it cannot restore vision already lost. First-line treatment is usually daily eye drops. The most effective and commonly used are prostaglandin analogues (latanoprost, bimatoprost, travoprost), which increase fluid drainage from the eye and are used once daily. Other drop classes include beta-blockers (timolol), carbonic anhydrase inhibitors (dorzolamide) and alpha-2 agonists (brimonidine). Selective laser trabeculoplasty (SLT) — a 5–10 minute outpatient laser treatment to the drainage angle — is now recommended by NICE as a first-line treatment option alongside or instead of drops for newly diagnosed POAG. It reduces IOP by approximately 25–30% and lasts on average three to five years, after which it can be repeated. Surgery (trabeculectomy — creating a new drainage channel, or minimally invasive glaucoma surgery, MIGS) is used when drops and laser are insufficient. ## Glaucoma and global blindness In the UK, glaucoma is detected early through routine eye examinations and managed with affordable treatments — eye drops, laser and surgery are all available on the NHS. Blindness from glaucoma in the UK is uncommon with appropriate treatment. In low-income countries, the picture is entirely different. There is a severe shortage of ophthalmologists; tonometers and OCT equipment are absent from most district hospitals; and the cost of long-term daily eye drops is unaffordable for the rural poor. Glaucoma blindness is irreversible — unlike cataract blindness, which can be cured surgically. This makes early detection and treatment in low-resource settings even more urgent. World Aid Network funds eye care — including glaucoma screening and treatment — for poor patients through locally-licensed ophthalmologists. ## Key takeaways - Glaucoma is the second leading cause of blindness worldwide, affecting around 80 million people globally and approximately 700,000 in the UK — with up to half undiagnosed. - Primary open-angle glaucoma (POAG) is painless and symptom-free until advanced. Peripheral vision is lost silently over years. Regular eye tests are the only way to detect it early. - NHS free eye tests for glaucoma risk are available for those over 60, those over 40 with a first-degree relative with glaucoma, and black Africans/Caribbeans over 40. - Treatment — prostaglandin analogue eye drops and/or selective laser trabeculoplasty (SLT) — lowers intraocular pressure and prevents further optic nerve damage but cannot restore lost vision. - Glaucoma blindness is irreversible. In low-income countries, lack of screening and unaffordable treatment means preventable blindness from glaucoma is common. ## Frequently asked questions ### What is glaucoma? Glaucoma is a group of eye conditions in which the optic nerve — which transmits visual information from the eye to the brain — is progressively damaged, most commonly as a result of raised intraocular pressure (IOP). This damage causes irreversible loss of peripheral vision, gradually narrowing the visual field, and can lead to total blindness if untreated. Glaucoma is the second leading cause of blindness worldwide, affecting approximately 80 million people globally. ### What are the symptoms of glaucoma? Primary open-angle glaucoma — the most common type — has no symptoms in its early or middle stages. Peripheral vision is lost silently and gradually; by the time most patients notice visual changes, significant irreversible damage has already occurred. Advanced POAG causes tunnel vision and, eventually, complete blindness. Acute angle-closure glaucoma is very different — it presents suddenly with severe eye pain, headache, nausea, vomiting, blurred vision and halos around lights, and is a medical emergency. ### What causes glaucoma? Most cases of glaucoma are caused by impaired drainage of aqueous humour — the fluid produced inside the eye — leading to raised intraocular pressure (IOP) that damages the optic nerve. In primary open-angle glaucoma, the trabecular meshwork drainage tissue becomes progressively less efficient with age. In acute angle-closure glaucoma, the drainage angle physically closes. In normal tension glaucoma, the mechanism of nerve damage is less clear — the optic nerve appears abnormally vulnerable even at normal IOP. ### Who is at highest risk of glaucoma? Key risk factors for primary open-angle glaucoma include: raised intraocular pressure (ocular hypertension); a first-degree relative with glaucoma (approximately 10 times higher risk); age over 60; black African or Caribbean ethnicity (higher prevalence and earlier onset); myopia (short-sightedness); diabetes; and long-term use of steroid eye drops or oral steroids. Angle-closure glaucoma is more common in people who are long-sighted (hyperopic) and in those of East Asian ethnicity. ### Is glaucoma hereditary? Yes. Having a first-degree relative (parent, sibling or child) with glaucoma increases your risk by approximately 10 times. Multiple genes have been identified that increase glaucoma susceptibility. Because of this family history risk, the NHS provides free eye tests to everyone aged 40 and over with a first-degree relative who has glaucoma. If a close family member has been diagnosed, it is important to inform your optician and ensure you have regular eye examinations. ### How is glaucoma diagnosed? Glaucoma is diagnosed through a comprehensive eye examination including: tonometry (IOP measurement); optic disc examination — an ophthalmologist or optometrist looks for characteristic damage to the optic disc, including cupping and pallor; visual field testing (automated perimetry) to map peripheral vision loss; and OCT (optical coherence tomography) to detect thinning of the retinal nerve fibre layer — often the earliest detectable sign of glaucomatous damage. Diagnosis is based on the combination of these tests, not on IOP alone. ### Who is entitled to a free NHS eye test for glaucoma? The NHS provides free sight tests for people at elevated glaucoma risk: anyone aged 40 or over with a first-degree relative (parent, sibling or child) who has glaucoma; all people aged 60 and over; people of black African or Caribbean heritage aged 40 and over (due to higher prevalence and earlier onset); and anyone with a suspected or confirmed glaucoma diagnosis. All optician referrals via the NHS sight test pathway are also free of charge. ### What are the types of glaucoma? The main types are: primary open-angle glaucoma (POAG) — the most common type, causing slow, painless, progressive peripheral vision loss; acute primary angle-closure glaucoma — sudden closure of the drainage angle causing a rapid, severe pressure rise and a painful emergency; normal tension glaucoma — optic nerve damage despite statistically normal IOP; ocular hypertension — raised IOP without detectable optic nerve damage or vision loss (a risk factor for POAG); and secondary glaucoma — raised IOP caused by another condition such as uveitis, trauma or neovascularisation from diabetic retinopathy. ### What is acute angle-closure glaucoma and how is it treated? Acute angle-closure glaucoma is a medical emergency requiring immediate hospital treatment. The iris blocks the drainage angle of the eye, causing a sudden and dramatic rise in intraocular pressure (sometimes above 50 mmHg, versus a normal of approximately 10–21 mmHg). Symptoms — severe eye pain, headache, nausea, vomiting, blurred vision, haloes around lights — come on suddenly and may be mistaken for migraine. Treatment begins with intensive IOP-lowering drops and intravenous acetazolamide; definitive treatment is an Nd:YAG laser iridotomy — creating a small hole in the iris to restore fluid drainage. The fellow eye is treated prophylactically. ### What is the treatment for glaucoma? Glaucoma treatment aims to lower IOP to a level at which further optic nerve damage is prevented. First-line treatment is prostaglandin analogue eye drops (latanoprost, bimatoprost or travoprost) — used once daily, they increase aqueous drainage and reduce IOP by 25–35%. Selective laser trabeculoplasty (SLT) is a NICE-approved first-line alternative or addition to drops. Surgery (trabeculectomy or minimally invasive glaucoma surgery, MIGS) is used when drops and laser are insufficient. No treatment can restore vision already lost to glaucoma. ### What are glaucoma eye drops? Glaucoma eye drops lower intraocular pressure by either increasing fluid outflow from the eye or reducing its production. The most effective and commonly prescribed class is prostaglandin analogues (latanoprost, bimatoprost, travoprost) — used once daily in the evening. Other classes include: beta-blockers (timolol — used twice daily, avoid in asthma); carbonic anhydrase inhibitors (dorzolamide, brinzolamide); and alpha-2 agonists (brimonidine). Combinations are used when single drops are insufficient. Consistent daily use is essential — missing doses allows IOP to rise and nerve damage to continue. ### What is selective laser trabeculoplasty (SLT)? SLT is a 5–10 minute outpatient laser procedure in which a low-energy laser is applied to the trabecular meshwork (drainage tissue) of the eye to improve aqueous outflow and reduce IOP. NICE recommends SLT as a first-line treatment option for newly diagnosed POAG alongside or instead of drops. SLT reduces IOP by approximately 25–30%, is well-tolerated and can be repeated if the effect wears off (typically after three to five years). It has no systemic side effects and carries a very low risk of complications. ### What is glaucoma surgery? Surgery is used when IOP remains uncontrolled despite drops and laser. Trabeculectomy — the most established surgical procedure — creates a new drainage channel under the upper eyelid conjunctiva (a 'bleb') to allow aqueous humour to drain out of the eye and be absorbed. It reduces IOP significantly and requires careful post-operative management. Minimally invasive glaucoma surgery (MIGS) encompasses newer, gentler procedures — including iStent, XEN gel stent and OMNI — which are safer but provide more modest IOP reduction. Glaucoma tube shunts (valves) are used in complex cases. ### Can glaucoma be cured? No. There is currently no cure for glaucoma. Treatment — eye drops, laser and surgery — lowers intraocular pressure and prevents or slows further optic nerve damage, but cannot restore vision already lost. With early diagnosis and good IOP control, the majority of patients with glaucoma retain useful vision throughout their lifetime. This is why regular eye tests are so important — glaucoma that is caught early can be treated before significant damage occurs. ### Will I go blind from glaucoma? With regular monitoring and adherence to treatment, blindness from glaucoma is uncommon in the UK. The goal of treatment is to lower IOP sufficiently to halt or minimise further optic nerve damage. Studies show that with good IOP control, vision remains stable in the large majority of patients over many years. However, if glaucoma is undiagnosed, treatment is inconsistent or IOP control is poor, progressive vision loss and eventual blindness can occur. This is why compliance with treatment and regular follow-up appointments are critical. ### How does glaucoma affect peripheral vision? In primary open-angle glaucoma, the nerve fibres serving peripheral (side) vision are typically damaged first. Patients lose vision from the nasal and superior peripheral fields inward — initially as small 'scotomas' (blind spots) that are often not consciously noticed. As damage progresses, the visual field narrows ('tunnel vision'). In end-stage glaucoma, only a small central island of vision may remain before total blindness. The central vision used for reading and facial recognition is preserved until late stages — which is why many patients are unaware of early glaucoma. ### What is normal tension glaucoma? Normal tension glaucoma (NTG) is a form of POAG in which typical optic nerve damage and visual field loss occur despite an intraocular pressure within the statistically normal range (10–21 mmHg). It is thought that in NTG, the optic nerve is abnormally sensitive to pressure, or that other factors such as impaired blood flow to the nerve contribute to damage. Treatment — lowering IOP below the normal range with drops, laser or surgery — is still effective at slowing NTG progression. NTG is more common in people of Japanese ethnicity. ### Is glaucoma more common in people of black African or Caribbean heritage? Yes. Primary open-angle glaucoma is significantly more prevalent in people of black African and Caribbean ancestry — approximately three to four times more common than in white Europeans — and tends to present at a younger age and progress more rapidly. For this reason, the NHS provides free eye tests for black Africans and Caribbeans from age 40 (rather than the standard 60 for general free NHS eye tests). Regular eye examinations from age 40 are particularly important for people of black African or Caribbean heritage. ### How does glaucoma affect people in developing countries? In low-income countries, glaucoma is frequently undetected until it has caused severe, irreversible vision loss or blindness. Tonometers, OCT equipment and visual field analysers are absent from most district hospitals. Long-term eye drops — the mainstay of treatment — are unaffordable and inconsistently supplied. Unlike cataract blindness, which is reversible with surgery, blindness from glaucoma cannot be undone. World Aid Network funds eye care — including glaucoma treatment — for poor patients through locally-licensed ophthalmologists. ## How you can help World Aid Network funds sight-restoring eye care for poor patients in Pakistan, Indonesia and Malaysia through locally-licensed surgeons. Donate at https://worldaidnetwork.org/donate --- This is general information, not medical advice, published by World Aid Network. Always consult a qualified clinician about your own health.