Quick Answer
Ophthalmology contributes 6–8 NEET PG questions per paper, with glaucoma, cataract, and refractive errors covering nearly half of them. The high-yield framework:
- POAG — chronic, painless, open-angle, bilateral; cup-disc ratio >0.6 or asymmetry >0.2 between eyes; visual field defects (nasal step, arcuate scotoma).
- PACG — acute pain, halos, nausea, hard red eye, fixed mid-dilated pupil; emergency IOP-lowering + laser peripheral iridotomy.
- IOP — Goldmann applanation gold standard; normal 10–21 mmHg.
- First-line glaucoma drug — prostaglandin analogs (latanoprost).
- Surgical glaucoma — trabeculectomy still standard; MIGS for mild-moderate; cyclodestruction for refractory.
- Cataract — phacoemulsification + foldable IOL is standard; types include nuclear, cortical, posterior subcapsular.
- Refractive errors — myopia (concave lens), hyperopia (convex), astigmatism (cylindrical), presbyopia (age-related accommodation loss).
Glaucoma, cataract, and refractive errors collectively account for the majority of preventable blindness globally and dominate NEET PG ophthalmology questions. India alone has more than 12 million blind people, with cataract still the leading cause despite the Indian National Programme for Control of Blindness (NPCB) — making this material both clinically essential and exam-critical. This NEETPGAI ultimate guide consolidates the disease pathophysiology, modern diagnostic tools (OCT, visual fields), medical and surgical ladders, and the high-yield exam pearls examiners revisit every year.
Pair this article with the Ophthalmology subject hub and the retina and uveitis guide for comprehensive eye-disease preparation. Distinguishing POAG from PACG, recognising acute angle closure as an ocular emergency, and knowing when phacoemulsification is contraindicated are the most frequently tested concepts on NEET PG 2026.
Glaucoma — definition and classification
Glaucoma is a progressive optic neuropathy characterised by retinal ganglion cell loss and corresponding visual field defects, typically (but not always) associated with raised IOP. It is the second leading cause of blindness worldwide.
Classification
| Type | Mechanism | Onset | Pain |
|---|
| Primary open-angle (POAG) | Trabecular outflow resistance | Insidious | None |
| Primary angle-closure (PACG) | Iridocorneal angle closure | Acute or subacute | Severe |
| Normal-tension | Vascular optic nerve damage at "normal" IOP | Insidious | None |
| Secondary open-angle | Pigment dispersion, pseudoexfoliation, steroid-induced, neovascular | Variable | Variable |
| Secondary angle-closure | Lens-induced (intumescent), uveitic, neovascular, malignant | Variable | Often |
| Congenital | Goniodysgenesis (Barkan membrane) | Birth–3 yr | Photophobia, buphthalmos |
Primary open-angle glaucoma (POAG)
The commonest glaucoma worldwide. Risk factors: age >40, family history (first-degree 4× risk), African ancestry, myopia, diabetes, thin central corneal thickness, baseline IOP.
Clinical features
- Asymptomatic until significant visual field loss has occurred.
- Bilateral but often asymmetric.
- Reduced peripheral vision long before central acuity loss.
Examination findings
- Optic disc cupping — cup-disc ratio >0.6, asymmetry >0.2 between eyes, neuroretinal rim thinning (ISNT rule violated: Inferior, Superior, Nasal, Temporal in order of thickness in healthy eyes).
- Visual field defects — paracentral scotoma, nasal step, arcuate (Bjerrum) scotoma, advanced tubular vision.
- OCT — RNFL (retinal nerve fibre layer) thinning is the most sensitive early finding.
- Gonioscopy — open angle (Shaffer grade 3–4).
Medical management ladder
- Prostaglandin analogs (latanoprost 0.005% OD, bimatoprost, travoprost) — first-line. Increase uveoscleral outflow. ~25–30% IOP reduction. Side effects: iris hyperpigmentation, eyelash growth, periorbital fat atrophy, conjunctival hyperaemia.
- Beta-blockers (timolol 0.5% BD) — reduce aqueous production. Avoid in asthma/COPD, bradycardia, heart block.
- Alpha-2 agonists (brimonidine) — reduce production, increase uveoscleral outflow. Risk of allergic conjunctivitis, drowsiness in children (avoid <2 yr).
- Topical CAIs (dorzolamide, brinzolamide) — reduce production. Sulfa allergy contraindication.
- Rho kinase inhibitors (netarsudil) — newer; increase trabecular outflow, reduce episcleral venous pressure.
- Pilocarpine (miotic) — historical; rarely first-line now.
Laser and surgical management
- Selective laser trabeculoplasty (SLT) — increasingly first-line per LiGHT trial; reduces IOP for years; can be repeated.
- Trabeculectomy — gold standard surgery. Creates a guarded fistula under a scleral flap; mitomycin C reduces fibrosis.
- Glaucoma drainage devices (Ahmed, Baerveldt) — for refractory or neovascular glaucoma.
- MIGS (minimally invasive glaucoma surgery) — iStent, Hydrus, Xen gel stent — for mild-moderate POAG, often combined with cataract surgery; faster recovery, fewer complications.
- Cyclodestruction (cyclophotocoagulation) — refractory or end-stage eyes.
Primary angle-closure glaucoma (PACG)
An ocular emergency. Risk factors: hyperopia (small eyes), Asian ethnicity, female, age >50, shallow anterior chamber, plateau iris configuration.
Acute attack
- Severe ocular pain, headache, nausea, vomiting (mimics gastritis or migraine).
- Coloured halos around lights.
- Hard, red eye on palpation.
- Fixed, mid-dilated, oval pupil.
- Corneal oedema, shallow anterior chamber.
- IOP often 50–80 mmHg.
Emergency management
- Topical: pilocarpine 2%, timolol, apraclonidine, prednisolone, dorzolamide.
- Systemic: acetazolamide 500 mg IV/oral, mannitol 1–2 g/kg IV (osmotic).
- Definitive: YAG laser peripheral iridotomy (LPI) — once cornea clears. Performed bilaterally as the fellow eye is at high risk.
- Cataract extraction is increasingly used as the definitive treatment because lens extraction deepens the anterior chamber.
IOP measurement and OCT
Tonometry
| Method | Notes |
|---|
| Goldmann applanation tonometry (GAT) | Gold standard; uses Imbert-Fick principle; influenced by central corneal thickness |
| Non-contact (air-puff) | Screening; less accurate at high IOP |
| iCare (rebound) | No anaesthesia needed; useful in children, bedridden |
| Tono-Pen | Handheld; useful in scarred or oedematous corneas |
| Schiotz (indentation) | Historical; rarely used |
Normal IOP: 10–21 mmHg. Diurnal variation up to 5 mmHg, peak in morning.
OCT (optical coherence tomography)
- High-resolution cross-sectional imaging of retina and optic nerve.
- RNFL thickness is the earliest objective sign of glaucomatous damage — often abnormal before visual field defects.
- Macular ganglion cell complex analysis adds sensitivity.
Visual fields (perimetry)
- Humphrey automated perimetry is standard. Reliability indices (fixation losses, false positives, false negatives) must be acceptable.
- Glaucomatous defects respect the horizontal midline (nasal step, arcuate, altitudinal — but altitudinal is more often vascular).
Cataract — types and management
A cataract is any opacity of the crystalline lens reducing vision. The leading cause of treatable blindness in India.
Risk factors
- Age-related (senile) — by far the most common; oxidative damage and fibre denaturation.
- Diabetes mellitus — accelerates cortical and posterior subcapsular cataract.
- Steroid use — classic posterior subcapsular cataract.
- UV light, smoking, alcohol.
- Trauma — rosette cataract.
- Congenital — TORCH, galactosemia, lowe syndrome, myotonic dystrophy.
- Secondary — uveitis, retinitis pigmentosa, intraocular tumours.
Morphological types
| Type | Features |
|---|
| Nuclear sclerotic | Yellow-brown lens nucleus; classic age-related; second sight (myopic shift) |
| Cortical | Spoke-like opacities; common in diabetes |
| Posterior subcapsular | Behind posterior capsule; symptoms with bright lights and reading; steroid- or diabetes-related |
| Christmas tree | Polychromatic crystalline; myotonic dystrophy |
| Sunflower | Wilson disease (copper deposition under anterior capsule) |
| Mature/hypermature | Total lens opacity; Morgagnian — liquefied cortex with sunken nucleus |
Surgical management
- Phacoemulsification + foldable IOL — global standard. Small clear-corneal or scleral incision (2.2–2.8 mm), ultrasonic emulsification of nucleus, irrigation-aspiration of cortex, IOL insertion in the capsular bag. Outpatient, sutureless.
- Manual small-incision cataract surgery (MSICS) — Indian innovation; cost-effective, rapid, used widely in NPCB camps. Outcomes comparable to phacoemulsification in skilled hands.
- Extracapsular cataract extraction (ECCE) — historical; large incision, sutured.
- Intracapsular cataract extraction (ICCE) — obsolete (no posterior capsule support, no posterior chamber IOL possible).
- Femtosecond laser-assisted cataract surgery (FLACS) — newer; precise capsulorrhexis and nucleus fragmentation. Cost-prohibitive in India.
IOL options
- Monofocal — single focal length; cheapest; spectacles needed for near.
- Toric — corrects astigmatism.
- Multifocal / EDoF (extended depth of focus) — spectacle independence; risk of halos and reduced contrast.
- Accommodative IOL — limited efficacy.
Posterior capsular opacification (PCO)
The most common late complication of phaco. Treated by YAG laser capsulotomy in clinic.
Refractive errors
The eye must focus parallel light rays on the retina to achieve a sharp image. Refractive errors result from mismatches between corneal/lens power and axial length.
Myopia (short-sightedness)
- Eye too long or refractive power too high; light focuses in front of the retina.
- Symptoms: blurred distance vision, clear near vision.
- Correction: concave (minus) lens, contact lenses, refractive surgery (LASIK, SMILE, PRK).
- High myopia (>−6 D) — increased risk of retinal detachment, lacquer cracks, choroidal neovascularisation, glaucoma.
- Myopia control in children: low-dose atropine 0.01%, orthokeratology, dual-focus contact lenses, increased outdoor time.
Hyperopia (long-sightedness)
- Eye too short; light focuses behind the retina.
- Children compensate by accommodation; symptoms (eyestrain, headaches) emerge as accommodation declines.
- Correction: convex (plus) lens.
- Refractive accommodative esotropia — uncorrected hyperopia in children causes excessive accommodation and convergence; full hyperopic correction is curative.
Astigmatism
- Unequal corneal curvature in different meridians.
- Types: regular (with-the-rule, against-the-rule, oblique) and irregular (keratoconus, scarring, post-surgical).
- Correction: cylindrical lenses, toric contact lenses, refractive surgery.
Presbyopia
- Age-related loss of accommodation due to lens stiffening.
- Onset around 40 years.
- Correction: reading glasses, bifocals, progressive lenses, multifocal IOL.
Refractive surgery options
- LASIK — most common; flap created with microkeratome or femtosecond laser, stromal ablation with excimer laser. Range: −1 to −10 D, mild hyperopia, up to 6 D astigmatism.
- PRK (photorefractive keratectomy) — surface ablation; longer healing, but better for thin corneas, military or contact-sport candidates.
- SMILE (small incision lenticule extraction) — femtosecond laser creates a lenticule extracted through a 2 mm incision; flapless.
- Phakic IOL — for high myopia (>−10 D) where corneal ablation is unsafe.
High-yield NEET PG MCQ traps
- Cup-disc ratio threshold — >0.6 or asymmetry >0.2 between eyes is suspicious.
- First-line glaucoma drug — prostaglandin analog (latanoprost), once daily, no systemic side effects.
- Pilocarpine in PACG — induces miosis; pulls iris away from angle; useful in acute attack.
- Timolol contraindication — asthma, COPD, bradycardia, heart block (systemic absorption).
- Brimonidine in children — avoid <2 years (CNS depression, apnea).
- Steroid-induced glaucoma — posterior subcapsular cataract + open-angle IOP rise.
- Phacomorphic glaucoma — intumescent cataract pushes iris-lens diaphragm; treat by cataract extraction.
- Pseudoexfoliation syndrome — flaky white material on lens capsule and pupil margin; "secondary open-angle" with worse prognosis and high cataract surgery complications (zonular weakness).
- Buphthalmos — congenital glaucoma; large eye, cloudy cornea (Haab striae), photophobia, epiphora.
- Galactosemic cataract — "oil droplet" cataract; reversible if galactose is removed early.
Recent updates
- LiGHT trial (2019, 6-yr update 2023): SLT as first-line for POAG and ocular hypertension is at least as effective as drops, with better quality of life.
- EAGLE trial (2016): clear lens extraction is more effective than LPI alone for newly diagnosed PACG with IOP >30.
- Preservative-free formulations are increasingly preferred in long-term glaucoma therapy to reduce ocular surface disease.
- Indian context: the National Programme for Control of Blindness (NPCB-VI) targets cataract surgical rate (CSR) of 6500 per million, with phacoemulsification overtaking MSICS in urban centres while MSICS remains the rural workhorse.
- Atropine 0.01% for myopia control is now mainstream in Indian pediatric practice (LAMP study).
Frequently asked questions
How do you differentiate POAG from PACG?
POAG is chronic, painless, bilateral, and silent until late vision loss. PACG presents acutely with severe pain, halos around lights, nausea, and a hard, red eye with fixed mid-dilated pupil. Gonioscopy distinguishes them: open angle in POAG, closed (or occludable) angle in PACG. PACG needs immediate IOP reduction and laser peripheral iridotomy.
Which IOP measurement is the gold standard?
Goldmann applanation tonometry (GAT) remains the gold standard for IOP measurement, normal 10 to 21 mmHg. It uses Imbert-Fick principle and is influenced by central corneal thickness — thicker corneas overestimate, thinner underestimate. Non-contact (air-puff) tonometry is useful for screening but less accurate. iCare rebound tonometers are practical alternatives.
What is the first-line medical therapy for POAG?
Prostaglandin analogs (latanoprost, bimatoprost, travoprost) are first-line — once daily dosing, lowest IOP reduction of about 25 to 30%, no systemic side effects. Adverse effects include iris hyperpigmentation, eyelash lengthening, periorbital pigmentation. Beta-blockers (timolol) are alternative but contraindicated in asthma, COPD, and bradyarrhythmia.
What is the most common type of cataract surgery today?
Phacoemulsification with foldable intraocular lens implantation through a small clear-corneal or scleral incision (around 2.2 to 2.8 mm) is the worldwide standard. It allows rapid visual recovery, suture-less wound, and astigmatism control. Femtosecond laser-assisted cataract surgery (FLACS) is an emerging refinement but cost-prohibitive in India.
What refractive error causes presbyopia?
Presbyopia is age-related loss of accommodation due to lens stiffening, typically beginning around age 40. It is not a true refractive error but an accommodative deficit. Correction is with reading glasses (plus lens), bifocals, progressive lenses, or multifocal IOLs. Distinguish it from hyperopia, where the eyeball is too short and distance correction is also needed.
This content is for educational purposes for NEET PG exam preparation. It is not a substitute for professional medical advice, diagnosis, or treatment. Clinical information has been reviewed by qualified medical professionals.
Written by: NEETPGAI Editorial Team
Reviewed by: Pending SME Review
Last reviewed: April 2026
