Glaucoma

What is glaucoma?

Glaucoma is damage to the optic nerve that can cause permanent loss of vision. The optic nerve carries visual information from the eye to the brain. The Irish College of Ophthalmologists stresses that established nerve damage cannot be reversed, making early detection and treatment important even when your eyes feel comfortable and everyday sight seems clear. [1][21]

The common chronic forms develop gradually, often without an obvious warning. Reading an eye chart well does not establish that the whole visual field is healthy. A comprehensive examination checks the optic nerve and the area you can see, rather than treating a sharp central image as proof that glaucoma is absent. [18]

Glaucoma care aims to preserve useful vision over your lifetime. Ireland’s HSE/ICO Model of Eye Care describes it as a condition requiring continuing assessment and treatment. A diagnosis therefore starts a long-term plan; it does not automatically mean that you will lose your independence or require an operation. [2][21]

Open-angle glaucoma, ocular hypertension and narrow angles

Primary open-angle glaucoma has an open drainage angle but characteristic damage to the optic nerve and its nerve-fibre layers. Some affected people have pressure readings within the usual range: normal-tension glaucoma remains glaucoma. The diagnosis depends on the pattern of damage and examination, not simply on whether pressure is labelled high. [6][23]

Ocular hypertension means raised eye pressure without established glaucomatous damage. A glaucoma suspect may instead have a suspicious nerve appearance or test result. AAO guidance recommends assessing the overall risk and looking for change before deciding whether observation or treatment is appropriate. Neither label should be confused with a confirmed prediction of future blindness. [7]

Angle-closure disease involves narrowing or obstruction of the drainage angle and has a different treatment pathway. It can be chronic or present as an acute attack. Gonioscopy, an examination of the angle with a special lens, helps distinguish these conditions; an open-angle laser recommendation should not be transferred automatically to a narrow-angle eye. [8]

Who should have an assessment?

Family history, increasing age, raised pressure, myopia and certain optic-nerve or corneal findings can increase concern. Bring details of relatives with glaucoma, previous eye injuries and all medicines, including steroids. These factors help interpret the examination; none establishes the diagnosis by itself or justifies stopping a prescribed medicine without advice. [7][12]

Raised pressure increases risk, but many people with ocular hypertension do not develop glaucoma during follow-up. In OHTS, glaucoma developed in 4.4% of people using pressure-lowering medication and 9.5% of those initially observed over 60 months. These figures concern people who started with high pressure but no glaucoma damage, rather than the outlook for established glaucoma. [12]

The practical decision is whether your risk warrants treatment now or careful observation. AAO’s glaucoma-suspect guidance considers pressure, nerve and field findings, risk factors and evidence of change together. Ask which finding prompted the referral and what would lead the clinician to change the plan; a suspect label alone is not a treatment schedule. [7]

Symptoms and the limits of a visual-field illustration

Early glaucoma may be symptomless, so waiting for pain or obvious tunnel vision can delay diagnosis. Later damage can affect parts of the scene you are trying to see, while the other eye and familiar surroundings make some changes less noticeable. Routine examinations remain important even when you can read, work or drive without an obvious difficulty. [1][18]

A field test measures sensitivity at selected locations while you look at a central target. It is different from a glasses prescription or a retinal photograph. AAO recommends functional field testing alongside structural assessment, because what the nerve looks like and how well the visual field functions provide complementary information. [19][22]

The interactive illustration shows an example of patchy loss and reduced awareness around a scene. Its slider is an educational control, not a glaucoma stage, probability or measurement of your sight. Glaucoma does not produce an identical black tunnel in every person; the illustration cannot diagnose disease, reproduce your experience or establish whether driving is safe. [24]

What happens during a glaucoma assessment?

In general clinical guidance, assessment considers your history with visual acuity, pressure measurement, optic-nerve examination, gonioscopy and appropriate visual-field testing. Corneal thickness and imaging can add useful context. The AAO examination benchmarks support combining these findings rather than making the diagnosis from an air-puff pressure result or an isolated scan classification. The tests described here are general diagnostic methods, not a promised first-visit package. [19][22]

Goldmann applanation tonometry measures eye pressure at the surface of the cornea. Corneal properties influence interpretation, so a thickness measurement can contribute to risk assessment. EGS advises that imaging of the drainage angle does not replace gonioscopy. Tell the examiner about contact lenses, previous laser vision correction and difficulties completing earlier tests. [4]

OCT images the optic nerve, retinal nerve-fibre layer and related retinal structures. A field test assesses visual function. AAO describes these as complementary tools for monitoring progression. Bring previous scans and field results where possible: consistent comparisons over time are more informative than assuming that a single colour-coded report proves stability or deterioration. [6][19]

Why lower pressure, and what is my target?

Lowering eye pressure is the established way to reduce the risk of glaucomatous deterioration. In the Early Manifest Glaucoma Trial, immediate treatment delayed progression compared with initially withholding treatment. That finding supports treating the disease before a person notices further loss; it does not mean that every treated eye will remain unchanged. [14]

Your target pressure is an individual treatment goal, not a universal number separating safe from unsafe eyes. EGS recommends estimating it for each eye and reviewing it as the disease or general health changes. The amount of existing damage, rate of change, expected lifetime and treatment burden all influence the discussion. [4]

AAO describes an initial reduction of 20%–30% below baseline as a reasonable starting goal for primary open-angle glaucoma, adjusted for severity and course. This is a guideline starting point, not your prescription. If fields or the nerve worsen despite reaching the original target, the clinician may recommend a lower target or different treatment. [6]

SLT and what the LiGHT trial actually found

Selective laser trabeculoplasty, or SLT, treats the eye’s drainage tissue to improve fluid outflow and lower pressure. It can be used before drops or alongside them. NICE recommends it for suitable newly diagnosed, non-advanced chronic open-angle glaucoma, with important exclusions and a separate pathway for advanced disease. Suitability is determined by examination. [5][16]

In the LiGHT trial, 74.2% of patients initially allocated to SLT needed no pressure-lowering drops to maintain target pressure at 36 months. The trial recruited people with previously untreated open-angle glaucoma or ocular hypertension. This supports offering a laser-first discussion; it is not a promise that a particular eye will remain drop-free after one treatment. [10]

At six years, 69.8% of eyes initially treated with SLT remained at or below target pressure without drops or surgery. This result counts eyes; the earlier three-year result counts people, so the percentages cannot be compared directly. Repeat laser was allowed. The finding does not mean that one laser session provides permanent control. [11]

Cochrane found that trabeculoplasty may slow visual-field loss compared with drops, while noting differences between studies and laser types. Researchers also re-examined LiGHT field tests in a later analysis published in 2026, finding less average deterioration with laser first. This adds information from the original study; it is not a separate trial in a new group of patients. [9][20]

Using glaucoma drops safely and consistently

Pressure-lowering drops remain an effective option when laser is unsuitable, declined or insufficient. The placebo-controlled UK Glaucoma Treatment Study found that latanoprost preserved visual fields better than placebo. Treatment choice still depends on your eye, other health conditions and tolerance; the evidence does not imply that every person needs the same medicine. [13]

A practical technique matters. Wash your hands, check the bottle and correct eye, form a pocket with the lower lid, and avoid touching the tip to your eye or lashes. Moorfields advises waiting at least 5 minutes between different drops. Follow each product’s storage and opening-expiry instructions rather than assuming every bottle has the same usable life. [17]

Tell the team if drops sting persistently, cause redness, are difficult to squeeze or do not fit your routine. Medicine choice should consider allergies, interactions and health conditions. Changing the preparation, providing an aid or reviewing technique can help; silently abandoning treatment leaves the clinician without an accurate picture of your pressure control. [5][17]

When might glaucoma surgery be discussed?

Surgery is considered when the likely benefit of stronger pressure control outweighs its risks and burden. Advanced glaucoma may require a different starting approach from early disease. Procedures include operations that create a new drainage route and other techniques selected for the eye; the appropriate option depends on the pressure target and clinical circumstances. [15][6]

In the Treatment of Advanced Glaucoma Study, people starting with trabeculectomy had less disease worsening after five years than those starting with medicines. Both groups gave broadly similar answers about how vision affected everyday life. The study involved advanced glaucoma, so its findings do not mean that everyone with a new diagnosis should start with surgery. [15]

An operation aims to protect remaining sight, not rebuild an already damaged optic nerve. Discuss the proposed procedure, alternatives, potential complications and the support needed afterwards. Early follow-up and treatment adjustments can be important. General study results cannot provide a surgeon-specific success rate or determine the medicines and visit schedule for your own operation. [2][15]

How is follow-up planned?

Review timing depends on the risk of further loss, pressure control and evidence of progression. NICE gives a 12–18-month interval for controlled chronic open-angle glaucoma when no progression is detected and clinical risk is low, versus 6–12 months when risk is high. These are guideline examples for defined stable situations, not a local appointment promise. [5][4]

Uncontrolled pressure, uncertain change or established progression can require earlier reassessment. Repeating a field test may help separate real deterioration from test variability or establish a reliable baseline. EGS recommends considering the whole pattern over time; a stable pressure reading does not replace review of the visual field and optic nerve. [4]

Keep the monitoring appointments you are given, even if treatment feels successful. The HSE/ICO model describes lifelong glaucoma care, with care arrangements depending on stability and complexity. Bring current drops and tell the team about missed doses, new symptoms or difficulty attending, so the plan reflects what is actually happening between visits. [2]

Driving, independence and practical support in Ireland

Glaucoma does not automatically prevent driving, but formal assessment matters. For Irish Group 1 car and motorcycle drivers, the RSA requires a horizontal visual field of at least 120°, with specified extensions and no defects within the central 20°. Significant field loss can prevent meeting the standard even when you read an eye chart well. Other visual requirements also apply. [25]

Ask about mobility, reading and work difficulties rather than waiting until tasks become unmanageable. The aim is to protect vision and preserve quality of life while managing the burden of treatment. Practical changes, visual support and help using medicines can be discussed alongside pressure control; difficulty coping is a reason to ask for support, not to stop attending. [2][21]

Before your consultation, write down the questions that matter most: what type of glaucoma you have, which eye is affected, whether there is evidence of change, and how treatment will be judged. Bring previous eye records and a complete medicine list. AAO guidance includes ocular, family and systemic history because these details can alter decisions. [19]