Clinical Guides
Glaucoma
A clinically focused clinical guide to glaucoma classification, optic-nerve and visual-field diagnosis, pressure-targeted treatment, adherence, laser and surgery, pregnancy considerations, acute referral and equitable Indian eye care.
MedNext Academy | 15 min read
Glaucoma
A clinically focused clinical guide to glaucoma classification, optic-nerve and visual-field diagnosis, pressure-targeted treatment, adherence, laser and surgery, pregnancy considerations, acute referral and equitable Indian eye care.
Summary
Glaucoma is a group of progressive optic neuropathies in which retinal ganglion cells and their axons are lost, producing characteristic optic-nerve change and corresponding visual-field damage. Primary open-angle glaucoma (POAG) is typically chronic, bilateral but asymmetric and initially asymptomatic. The drainage angle is open on gonioscopy. Primary angle-closure disease involves iridotrabecular contact and can be chronic or present as an acute painful emergency. Secondary glaucomas arise from an identifiable ocular or systemic driver such as corticosteroid exposure, uveitis, trauma, neovascularisation, lens-related disease, pigment dispersion or pseudoexfoliation. Congenital and childhood glaucomas require paediatric specialist pathways.
Intraocular pressure (IOP) is the most important modifiable risk factor, but it is not the definition of glaucoma. Some people have ocular hypertension without optic neuropathy, while others develop damage at pressures within the population reference range. Diagnosis therefore integrates history, Goldmann-type applanation tonometry, central corneal thickness, slit-lamp and dilated optic-nerve assessment, standard automated perimetry and angle examination by gonioscopy. Optical coherence tomography supports structural assessment but does not replace clinical correlation or fields.
Treatment aims to preserve useful vision over the person's lifetime and is individualized by severity, rate of progression, baseline pressure, life expectancy, comorbidity, access and preference. A target pressure is an initial working estimate, not a permanent number; it is lowered further if credible progression occurs. Options include selective laser trabeculoplasty, topical pressure-lowering medicines, trabeculectomy, drainage devices and selected minimally invasive procedures. Adherence, instillation technique, monitoring and affordability determine real-world effectiveness. Acute angle closure, sudden visual loss, painful red eye, very high pressure with symptoms or rapidly progressing advanced disease requires urgent ophthalmic care.
How Common Is It?
Glaucoma is a major cause of irreversible visual impairment because established neural loss cannot be restored and early disease is usually silent. Global burden estimates differ by case definition, age range, examination method and population structure. WHO identifies glaucoma among the leading causes of distance vision impairment and blindness; the relevant public-health message is not a single immutable total but the large avoidable burden from delayed detection and incomplete long-term care. Prevalence rises strongly with age, so absolute burden increases as populations age.
Indian government primary-eye-care guidance treats glaucoma screening, referral and follow-up as components of the National Programme for Control of Blindness and Visual Impairment pathway. India contains diverse ancestry, rurality, deprivation and service availability; small regional prevalence studies should not be presented as a precise national count. Both open-angle and angle-closure disease matter. Angle closure is proportionally more prominent in many Asian populations than in European-derived populations and can cause severe bilateral loss, while POAG remains an important chronic burden. A high proportion of disease can remain undiagnosed until advanced because central acuity may stay normal while peripheral fields deteriorate.
Clinic attendance figures underestimate people who have never undergone a complete eye examination. Conversely, a raised pressure found during opportunistic screening is not equivalent to glaucoma. Detection programmes must avoid both false reassurance from a normal air-puff reading and overdiagnosis from one elevated value. Current guidelines recommends repeat measures in non-urgent situations and referral based on optic-nerve damage, a compatible field defect or confirmed Goldmann-type IOP at the relevant threshold. Local services may use referral refinement, but the defining problem remains loss of optic-nerve structure or function and lifetime risk, not merely the number of screened eyes.
Risk Factors
Age, higher IOP, family history in a first-degree relative, thinner central cornea and ancestry associated with increased susceptibility are established risk factors for open-angle disease. Myopia, optic-disc appearance, reduced ocular perfusion and some systemic vascular conditions can modify assessment, although associations do not prove causation in an individual. Central corneal thickness affects both measured pressure and risk estimation: a thin cornea can lead to underestimation by applanation and is independently associated with conversion in ocular hypertension studies, but simplistic correction tables should not be used to manufacture a supposedly true IOP.
Angle-closure risk relates to ocular anatomy and lens position. Increasing age, female sex, family history, hypermetropia, a shallow anterior chamber and short axial length increase suspicion. Gonioscopy determines whether the angle is open or occludable; symptoms alone cannot classify it. Medicines that cause pupillary dilation or alter uveal/lens configuration can precipitate closure in susceptible eyes, including some anticholinergic, adrenergic, sulfonamide-derived and serotonergic agents through different mechanisms. Patients should not stop essential systemic medicines without clinical advice, but acute ocular symptoms after a new drug require urgent review.
Secondary glaucoma risk follows the underlying mechanism. Topical periocular, inhaled, systemic and even potent dermatological corticosteroids can raise IOP in responders; duration, potency, route and personal susceptibility matter. Uveitis can raise pressure from inflammation, scarring or treatment. Trauma may cause angle recession years before glaucoma appears. Retinal ischaemia from diabetes or vein occlusion can drive neovascular glaucoma. Pseudoexfoliation and pigment dispersion accelerate outflow obstruction. Previous surgery, lens disorders and congenital anomalies also matter. Risk factors guide how intensively to assess and monitor; none authorizes a diagnosis without demonstrable clinical evidence.
Diagnosis
History
Ask about visual difficulty, field loss, falls, night navigation, glare, intermittent blur, halos, eye pain, headache, nausea and prior red-eye attacks. Chronic POAG is often symptomless; absence of complaint is not reassurance. Record family history, prior pressure readings, eye trauma or surgery, uveitis, high myopia or hypermetropia, retinal vascular disease and all corticosteroid routes. Review diabetes, blood pressure, migraine or vasospastic symptoms, respiratory and cardiac disease, renal function, pregnancy intentions and the ability to instil and obtain drops. Establish adherence non-judgementally, including cost, supply and technique barriers.
Examination
Measure best-corrected acuity, pupils and relative afferent defect, and examine the anterior segment. Use Goldmann-type applanation tonometry when possible; note time, device and corneal factors. Measure central corneal thickness. Dilated stereoscopic optic-nerve assessment considers rim thinning or notching, retinal nerve-fibre-layer defects, disc haemorrhage and asymmetry, not cup-to-disc ratio alone. Perform gonioscopy in both eyes to classify angle anatomy and identify pigmentation, synechiae, neovascularisation, recession or pseudoexfoliation. Van Herick estimation or anterior-segment OCT can triage angle depth but does not fully replace gonioscopy.
Investigations
Standard automated perimetry establishes functional damage and a baseline; unreliable or unexpected defects require repetition and correlation with anatomy. OCT of the nerve-fibre and ganglion-cell layers documents structure, but segmentation error, high myopia, disc size and age-related normative databases can mislead. Photograph or image the disc for longitudinal comparison. Diagnosis of POAG requires a compatible optic neuropathy and field pattern with an open angle after excluding secondary causes. Ocular hypertension means raised IOP without glaucomatous damage; a glaucoma suspect has concerning but insufficient findings. Normal-tension glaucoma is diagnosed only after confirming open-angle damage, measurement quality and plausible progression and excluding masquerades. Urgent symptoms require immediate pressure measurement and anterior-segment examination rather than routine serial testing.
Differential Diagnosis
Physiological cupping is often large but usually has a healthy rim, stable structure and no corresponding repeatable field defect. Disc size and family resemblance matter; a large disc naturally has a larger cup. High myopia can tilt the disc, distort OCT segmentation and produce non-glaucomatous field abnormalities. Optic atrophy from ischaemic, inflammatory, compressive, toxic, nutritional or hereditary neuropathy may mimic glaucoma. Pallor exceeding cupping, disproportionate acuity or colour loss, a central or vertical-meridian-respecting field defect, marked asymmetry, neurological signs or progression despite very low pressure should trigger neuro-ophthalmic reconsideration and imaging when indicated.
Retinal disease can create field or OCT abnormalities. Diabetic retinopathy, vascular occlusion, retinal detachment, macular disease and panretinal laser scars require fundus correlation. Media opacity can depress fields diffusely. Poor fixation, learning effect and fatigue create artefacts; a single abnormal field is rarely enough for chronic diagnosis. Optic-disc drusen may resemble rim change and produce field loss.
Classify the glaucoma mechanism rather than using the label generically. POAG has an open angle without an identified secondary cause. Angle-closure disease is defined by angle anatomy and may be acute, intermittent or chronic. Uveitic, neovascular, steroid-induced, traumatic, pseudoexfoliative, pigmentary and lens-associated glaucoma require treatment of the driver as well as pressure. Acute angle closure differs from conjunctivitis or migraine by the combination of pain, reduced vision, corneal oedema, abnormal pupil, shallow chamber and raised pressure, but presentations vary. Ocular hypertension is a risk state, not optic-nerve disease. Low measured IOP never rules out glaucoma, and high IOP never proves that visual loss is glaucomatous.
Management
Agree a lifetime plan based on diagnosis, stage, baseline untreated IOP where safely obtainable, damage in the better eye, progression rate, age, comorbidity and patient goals. Set an initial target pressure or percentage reduction that is expected to reduce progression risk. The target is revised after repeat fields, optic-nerve assessment and pressure measurements: credible progression at the apparent target means the target was insufficient, adherence or measurement needs reassessment, or the diagnosis requires review. Preserving function, not achieving a cosmetically normal number, is the outcome.
For newly diagnosed ocular hypertension or non-advanced COAG meeting treatment criteria, current guidelines offers 360-degree selective laser trabeculoplasty (SLT) as an initial option after discussion. SLT can reduce or delay drop burden, but effect varies, may diminish and does not remove monitoring. A prostaglandin analogue is a common first medicine when SLT is declined, unsuitable, unavailable, delayed or insufficient. Additional classes include topical beta-blockers, carbonic-anhydrase inhibitors, alpha-2 agonists, miotics in selected mechanisms and fixed combinations. Check response, tolerability, technique and actual access before escalating.
Progression despite feasible medical and laser therapy, advanced disease needing a low target, poor adherence not correctable by support or intolerance may require surgery. Trabeculectomy with antifibrotic modulation remains a major pressure-lowering operation; glaucoma drainage devices are used in selected refractory or high-risk eyes. Minimally invasive glaucoma surgery generally offers more modest lowering and evidence differs by device and combined cataract context. Angle-closure management includes iridotomy, lens-based or other mechanism-directed interventions and fellow-eye assessment; an acute attack is an emergency. Secondary glaucoma requires simultaneous management of inflammation, neovascular drive, trauma or medicine exposure. At every stage, provide low-vision rehabilitation and social support when damage limits function.
Prescribing Information
Choose an eye drop only after reviewing the glaucoma mechanism, target, ocular surface, pregnancy or breastfeeding, age, respiratory and cardiac history, renal status, other medicines, dexterity, cognition, cost and reliable local supply. Demonstrate one drop into the conjunctival sac without touching the bottle tip, eyelid closure and nasolacrimal occlusion to reduce systemic absorption. Observe teach-back. More drops are not better if the regimen cannot be followed; simplify timing, consider fixed combinations and distinguish non-adherence from pharmacological failure. Preservative load can worsen ocular-surface disease.
Prostaglandin analogues are commonly dosed once daily and can cause conjunctival hyperaemia, iris or periocular pigmentation, eyelash growth and periorbital change; use caution in relevant inflammatory or macular-oedema contexts. Topical beta-blockers can cause bradycardia, hypotension, fatigue and bronchospasm and may be unsafe in asthma, significant conduction disease or with systemic rate-limiting treatment. Alpha-2 agonists can cause allergy, dry mouth and somnolence and have paediatric safety restrictions. Topical carbonic-anhydrase inhibitors can sting or alter taste; systemic acetazolamide has renal, electrolyte, acid-base and hypersensitivity considerations and is generally a short-term or specialist tool. Miotics can cause brow ache, myopic shift and retinal or inflammatory concerns and are mechanism-specific.
Pregnancy evidence is limited because trials usually exclude pregnant people. No drop should be described as universally safe. Confirm gestation and breastfeeding, reassess whether treatment or SLT can reduce fetal exposure, use the minimum effective regimen selected with glaucoma and obstetric input, and apply punctal occlusion. Product labels and national references govern individual choices; brimonidine near delivery and beta-blocker or carbonic-anhydrase exposure require specific consideration. Do not abruptly stop sight-preserving therapy because of pregnancy without an alternative plan. Record brand, molecule, eye, frequency, response and adverse effects, and never use steroid-containing eye drops for a red eye without a diagnosis and pressure-aware follow-up.
When to Refer
Emergency ophthalmic referral is required for suspected acute angle closure: severe ocular pain or headache, reduced vision or coloured halos, nausea or vomiting, corneal haze, a mid-dilated poorly reactive pupil, shallow chamber or markedly raised IOP. Begin locally authorized emergency measures only when competent and do not delay transfer to obtain every test. Sudden vision loss, new afferent pupil defect, painful pressure elevation, trauma with raised IOP, severe uveitis, neovascularisation or postoperative pressure crisis also requires urgent specialist care.
Refer chronic suspected glaucoma after appropriate case-finding when there is suspicious optic-nerve damage, a repeatable compatible field defect or confirmed Goldmann-type pressure meeting the service threshold. Current guidelines advises that one non-contact tonometry value should not be the sole basis for referral and recommends repeating non-urgent IOP or field abnormalities when clinically appropriate. Angle abnormality, secondary features, childhood disease, advanced damage, rapid progression, monocular status or inability to generate reliable tests lowers the threshold. A consultant ophthalmologist should formulate the definitive plan for complex or sight-threatening disease and suitability for SLT or surgery.
Re-refer or escalate established disease when pressure is above the agreed target despite verified use, fields or nerve imaging show credible progression, drops are intolerable, supply is unreliable, the person cannot instil treatment, or pregnancy changes the risk-benefit balance. Do not discharge a patient merely because today’s IOP is low. If stable ocular hypertension or a resolved suspect is returned to primary eye care, give a clear summary and monitoring interval. In low-resource settings, referral urgency is determined by stage and symptoms, not by whether OCT is available; severe cupping, field constriction or threatened better-eye function warrants prompt specialist assessment.
Red Flags
A painful red eye with reduced vision, headache, halos, nausea, vomiting, corneal oedema or an abnormal pupil is acute angle closure until urgently excluded. It is not routine POAG and should not wait for the next clinic. A very high pressure can be asymptomatic, and a symptomatic eye can have only moderately raised pressure after partial resolution, so clinical context and gonioscopy matter. Bilateral symptoms after a new systemic medicine may signal a secondary angle mechanism that differs from pupillary block and needs specialist direction.
Chronic red flags include advanced field loss threatening fixation, severe damage in the better or only seeing eye, rapid progression, disc haemorrhage with change, marked asymmetry, and inability to attend or obtain treatment. New acuity or colour loss, optic-disc pallor out of proportion to cupping, a central field defect, a defect respecting the vertical meridian, proptosis, neurological signs or progression at unexpectedly low pressure suggests a non-glaucomatous optic neuropathy. Do not keep lowering pressure while ignoring a compressive or inflammatory lesion.
Medicine-related red flags include bronchospasm, syncope, clinically important bradycardia, severe allergy, confusion or profound lethargy. Eye pain, discharge or reduced vision after surgery or laser may indicate infection, inflammation or acute pressure change. In pregnancy, fetal concerns must be balanced with the risk of irreversible maternal visual loss through coordinated review. Social red flags are also clinical: running out of drops, using the wrong eye, inability to squeeze the bottle, unaffordable combinations, missed monitoring or unsafe driving with field loss can cause preventable harm. Ask directly and solve the barrier rather than labelling the patient non-compliant.
Indian Clinical Context
India’s glaucoma burden is amplified by late presentation, uneven distribution of ophthalmologists and testing equipment, travel costs and the chronic cost of medicines. The Ministry of Health and Family Welfare primary-eye-care model places screening, basic assessment and referral within linked community, vision-centre and specialist services. Implementation varies by state and district. A screening camp or air-puff pressure measurement is an entry point, not a definitive examination. Suspicious patients need optic-nerve assessment, fields and angle evaluation through a pathway capable of long-term follow-up.
Affordability and supply continuity can determine the best treatment. Generic medicines may reduce cost, but changes in bottle design, preservative, brand availability and refill access affect adherence and tolerability. Ask the patient to bring every bottle and demonstrate use. One bottle shared between relatives, unlabelled pharmacy substitutions and steroid-antibiotic combination drops used for recurrent redness are important hazards. SLT may reduce dependence on daily drops for suitable open-angle disease, but access, maintenance, trained operators and follow-up differ. Surgery can be highly effective yet requires counselling about postoperative visits, warning symptoms and the possibility of additional treatment.
Opportunistic case-finding is especially important for older adults, first-degree relatives, people with diabetes attending retinal care, high myopes and long-term corticosteroid users, while avoiding the claim that population screening by IOP alone prevents blindness. Use teleophthalmology and fundus imaging as referral support where validated, not as substitutes for gonioscopy or reliable fields. Record the better-eye functional risk, occupation, driving, literacy and caregiver support. Link patients with NPCBVI services, government hospitals, charitable eye networks or low-vision rehabilitation as locally available. Equity means designing a plan the patient can actually sustain, not choosing an ideal regimen that disappears after the first prescription.
NMC Competency Mapping
This guide supports the NMC ophthalmology domain covering glaucoma classification, clinical features, investigation, emergency recognition, pharmacology and principles of laser and surgery. Learners should distinguish ocular hypertension, a glaucoma suspect, POAG, angle-closure and major secondary glaucomas; perform or interpret visual acuity, pupils, anterior-segment examination, applanation pressure, optic-disc assessment and visual fields; and explain why gonioscopy is essential for mechanism. They should understand the uses and limitations of OCT and central corneal thickness rather than treating either as an automatic diagnostic answer.
Pharmacology integration includes prostaglandin analogues, beta-blockers, alpha-2 agonists, carbonic-anhydrase inhibitors and miotics, including systemic adverse effects, contraindications, combinations, punctal occlusion and adherence. Clinical skills include demonstrating drop instillation and communicating that treatment preserves remaining vision but does not restore lost field. Emergency outcomes include recognising acute angle closure and initiating immediate referral. Surgery teaching covers principles and indications of SLT, iridotomy, trabeculectomy, drainage devices and selected minimally invasive approaches without implying that all techniques are interchangeable.
Community-medicine and professionalism outcomes include avoidable-blindness programmes, referral pathways, accessibility, longitudinal records and respectful exploration of cost or literacy barriers. A useful workplace assessment asks the learner to construct a problem representation from nerve, field, angle and pressure data, set a reasoned initial target, choose a feasible treatment, counsel on technique and create a monitoring plan. Exact OP and PH competency identifiers and wording should be verified against the medical college’s current NMC CBME document before sign-off, because editions and local mapping tables may differ. Conceptual alignment does not replace direct observation of tonometry, disc examination or counselling competence.
Key Exam Pearls for NEET PG
Glaucoma is an optic neuropathy, not a synonym for raised IOP. Ocular hypertension has raised pressure without glaucomatous damage; normal-tension glaucoma has characteristic damage despite pressure within the statistical reference range. POAG requires an open angle on gonioscopy. Acute angle closure classically produces pain, red eye, reduced vision, halos, headache, vomiting, corneal oedema, a shallow chamber and a mid-dilated poorly reactive pupil; it is an emergency. Secondary mechanisms include steroids, uveitis, neovascularisation, angle recession, pseudoexfoliation, pigment dispersion and lens-related disease.
Goldmann applanation tonometry is the clinical reference method. A thin central cornea can underestimate measured IOP and alters risk, but correction nomograms do not create a certain true pressure. Optic-disc clues include focal rim notching, retinal nerve-fibre-layer loss, vertical cup enlargement, disc haemorrhage and inter-eye asymmetry. Field defects follow the retinal nerve-fibre anatomy: paracentral defects, nasal steps and arcuate scotomas can progress to tunnel vision. A defect respecting the vertical meridian or pallor exceeding cupping suggests a neurological mimic. OCT must agree with the disc and field.
IOP lowering is the only established modifiable treatment target. An individual target is revised downward if progression occurs. SLT is a first-line option for suitable newly diagnosed ocular hypertension or non-advanced COAG in current guidelines guidance; prostaglandin analogues are common first drops when laser is unsuitable or insufficient. Timolol can cause bronchospasm and bradycardia. Prostaglandins can darken the iris and alter eyelashes or periorbital tissues. Punctal occlusion reduces systemic absorption. Trabeculectomy creates a guarded filtration pathway; drainage devices are useful in selected refractory eyes. Laser iridotomy addresses pupillary block, not POAG. Pregnancy requires specialist risk-benefit planning, and a normal central acuity does not exclude advanced peripheral-field loss.
Frequently Asked Questions
Can someone have glaucoma when the eye pressure is within the normal range?
Yes. Glaucoma is diagnosed from characteristic optic-nerve damage and corresponding visual-field loss after considering the angle and other causes, not from pressure alone. Normal-tension glaucoma can progress at pressures within the population range. Conversely, ocular hypertension can exist without damage. Measurement quality, corneal thickness, repeated fields, optic-nerve imaging and the rate of change all inform the diagnosis and target.
Is selective laser trabeculoplasty a permanent cure that removes the need for monitoring?
No. SLT is an evidence-based first treatment option for suitable open-angle disease and can reduce or delay the need for drops, but response varies and may diminish. Some patients still need medicines, repeat laser or surgery. It does not restore lost vision and does not treat every glaucoma mechanism. Pressure, optic nerve and fields still require monitoring against an individualized target.
What should a patient do if glaucoma drops are unaffordable or difficult to use?
Tell the eye team before stopping. Cost, bottle design, tremor, arthritis, poor vision, memory, adverse effects and pharmacy supply are common treatment barriers, not moral failures. The clinician can verify technique, simplify timing, consider a generic or fixed combination, use an aid, involve a caregiver, assess suitability for SLT or surgery, and connect the patient with government, charitable or low-vision services.
Are glaucoma eye drops safe during pregnancy and breastfeeding?
No glaucoma drop is universally safe in every pregnancy. Evidence is limited, and the risk of fetal or neonatal exposure must be balanced against irreversible maternal sight loss. Do not stop treatment abruptly. Glaucoma and obstetric clinicians should review the mechanism, disease stage, gestation, product information and alternatives such as appropriately timed laser. The minimum effective regimen and nasolacrimal occlusion can reduce systemic exposure.
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