Ophthalmology essentials

In short

Ophthalmology is the study of the eye, the visual pathway and their disorders — refraction, cataract, glaucoma, cornea, retina, squint, ocular trauma and community eye health. It matters because cataract and uncorrected refractive error together cause the large majority of India's blindness and visual impairment, and both are cheaply curable: the National Blindness and Visual Impairment Survey 2015–19 put blindness prevalence at about 1.99% in the 50+ age group and 0.36% across all ages, both measured at the WHO <3/60 standard adopted in 2017 — figures vary with the definition, so always state which one is used. It is examined in the Phase 3 part 1 university paper (short notes, clinical cases, practicals: direct ophthalmoscopy, retinoscopy, visual field charting), in NExT/NEET-PG and in AIIMS/PGI entrances. Clinically it is used daily in district hospitals, Vision Centres, cataract camps, school eye screening and diabetic retinopathy screening, and in interviews for junior residency, LV Prasad/Aravind/Sankara Nethralaya fellowships and NPCBVI district programme posts.

Explained

Optics, refraction and refractive errors

• Emmetropia: parallel rays focus on the retina with accommodation at rest. Total dioptric power of the eye ≈ +60 D (cornea ≈ +43 D, lens ≈ +17 D); axial length ≈ 24 mm. A 1 mm change in axial length shifts refraction by about 3 D.
• Myopia (short sight): rays focus in front of the retina — axial (long eye, commonest), curvatural, index (nuclear cataract, diabetes) or positional. Corrected by a concave (minus) lens. Types: congenital, simple (school myopia, progresses till about 20 years), pathological/degenerative (>6 D, with lacquer cracks, Fuchs spot, lattice degeneration and a high risk of retinal detachment).
• Hypermetropia (long sight): rays focus behind the retina — axial (short eye), curvatural, index or aphakia. Corrected by a convex (plus) lens. Latent/facultative/absolute components; causes asthenopia, accommodative convergent squint and amblyopia in children, and predisposes to angle-closure glaucoma (shallow anterior chamber).
• Astigmatism: different meridians focus at different points. Regular (with-the-rule: vertical meridian steeper, corrected with minus cylinder axis ~180°; against-the-rule; oblique) corrected by cylindrical/toric lenses; irregular (keratoconus, corneal scar) needs rigid gas-permeable or scleral contact lenses.
• Presbyopia: age-related loss of accommodation from lens sclerosis; near add roughly +1.00 D at 40–45, +1.50 at 45–50, +2.00 at 50–55, +2.50 at 55–60, +3.00 beyond — always the minimum add that gives comfortable near vision.
• Anisometropia (unequal refraction) causes aniseikonia and amblyopia; aphakia (no lens: +10 to +12 D spectacle, hypermetropic, with ring scotoma and 25–30% magnification) versus pseudophakia (IOL implanted — the modern standard).
• Measurement: objective — retinoscopy (streak, at 1 m: subtract 1 D from gross), autorefraction, keratometry; subjective — trial frame, duochrome, Jackson cross-cylinder. In children under 8 and in accommodative squint, refraction must be under cycloplegia (atropine 1% or cyclopentolate).
• Refractive surgery: PRK, LASIK, femto-LASIK, SMILE (corneal), phakic IOL and refractive lens exchange for high errors. Contraindicated in keratoconus, thin cornea (residual stromal bed must stay above about 250–300 µm), unstable refraction and age under 18.

Visual acuity, visual fields and the definitions of blindness

• Distance acuity: Snellen chart at 6 m. Acuity = distance at which read / distance the normal eye reads it (6/6, 6/60). If the top letter is not read: walk the chart closer (3/60, 1/60), then counting fingers, hand movements, perception of light (PL/PR), then "no PL" = total blindness. LogMAR charts (ETDRS) are preferred for research — equal letter numbers per line, 0.1 logMAR per line; 6/6 = 0.0 logMAR, 6/60 = 1.0.
• Pinhole test separates refractive from organic causes; near vision by N notation (N6 normal).
• Visual fields: normal monocular extent ~60° up, 70–75° down, 60° nasal, 90–100° temporal; physiological blind spot 15° temporal. Perimetry — confrontation (bedside), Lister/Bjerrum tangent screen, Goldmann kinetic, and automated static (Humphrey 24-2, SITA) for glaucoma; field defects localise the lesion (see table in the formulas section).
• India's old programme definition of blindness was visual acuity worse than 6/60 in the better eye with available correction (i.e. the WHO category of severe visual impairment included) — it was revised in 2017 to the WHO standard: presenting acuity worse than 3/60 in the better eye, which made Indian and global data comparable and reduced the measured prevalence at a stroke. Moderate visual impairment = worse than 6/18 to 6/60; economic blindness 6/60 or worse; social blindness 3/60 or worse.
• Rights of Persons with Disabilities Act, 2016: "blindness" means total absence of sight, or acuity ≤3/60 (or <10/200 Snellen) in the better eye with best correction, or field limited to ≤10°; "low vision" is acuity 6/18–3/60 or field 10–40°. Benchmark disability (40%) governs reservation and certification.
• Colour vision: Ishihara pseudo-isochromatic plates (red-green), Farnsworth-Munsell 100-hue; required for railway, aviation, defence and driving fitness certification.

Cataract, the lens and IOL surgery

• Definition: any opacity of the lens or its capsule causing a drop in vision. Pathogenesis — oxidative damage, loss of lens epithelial pump, protein aggregation and hydration.
• Types: senile (commonest: cortical — cuneiform spokes, glare, "second sight" absent; nuclear — brunescent, index myopia; posterior subcapsular — early reading and glare difficulty), congenital/developmental (rubella, galactosaemia, hypocalcaemia, hereditary), traumatic (rosette), complicated (uveitis, retinitis pigmentosa — polychromatic lustre), metabolic (diabetes — snowflake; hypocalcaemic), toxic (steroids, chlorpromazine, miotics), radiation and after-cataract (posterior capsular opacification).
• Maturity: immature → mature → hypermature (Morgagnian, or sclerotic shrunken). Complications of neglect — phacomorphic glaucoma (swollen lens, angle closure), phacolytic/lens-protein glaucoma, subluxation, uveitis.
• Symptoms: painless progressive dimness, glare, monocular diplopia/polyopia, coloured haloes, difficulty in bright light (posterior subcapsular). Signs: leukocoria, absent or poor red reflex, iris shadow, opacity on slit-lamp and distant direct ophthalmoscopy.
• Pre-op workup: acuity and pinhole, pupillary reactions and projection of rays, sac syringing/ocular surface, slit lamp, IOP, fundus (or B-scan if media opaque), keratometry + axial length by optical or ultrasound biometry for IOL power, blood sugar and BP, dilated fundus of the fellow eye.
• Surgery: intracapsular (ICCE — obsolete), extracapsular (ECCE), small-incision cataract surgery (SICS) — manual, sutureless 6–7 mm scleral tunnel, the workhorse of Indian camps and high-volume centres, cheap and safe in hard cataracts; phacoemulsification — 2.2–2.8 mm incision, ultrasonic fragmentation, foldable IOL, fastest recovery; FLACS (femtosecond-assisted) in a few centres.
• IOLs: PMMA rigid, foldable acrylic/silicone, aspheric, toric (astigmatism), multifocal/EDOF (spectacle independence, but glare and haloes), posterior-chamber in-the-bag is standard; anterior-chamber or scleral/iris-fixated when there is no capsular support.
• Complications: operative — posterior capsule rupture, vitreous loss, nucleus drop, expulsive haemorrhage; early — striate keratopathy, iris prolapse, hyphaema, endophthalmitis (pain, hypopyon, falling vision days 2–7; treated with vitreous tap and intravitreal vancomycin + ceftazidime, ± vitrectomy); late — PCO (treated by Nd:YAG capsulotomy), cystoid macular oedema (Irvine-Gass), retinal detachment, IOL decentration, endothelial decompensation.
• Audit standard: a good unit should achieve 6/18 or better uncorrected/best-corrected in a large majority of eyes; the cataract surgical rate (CSR) in India is now above 6,000 per million per year in most states.

Glaucoma

• Definition: a progressive optic neuropathy with characteristic cupping and field loss, usually but not always with raised intraocular pressure. Normal IOP 10–21 mmHg (mean ~16, SD 2.5), diurnal variation <5 mmHg.
• Aqueous dynamics: secreted by the ciliary epithelium (active secretion, ultrafiltration, diffusion) ~2–2.5 µL/min; drains 80–90% by the trabecular meshwork → Schlemm canal → episcleral veins, 10–20% by the uveoscleral route.
• Primary open-angle glaucoma (POAG): insidious, bilateral, asymptomatic until advanced; open angle, raised IOP, cupping (vertical C:D >0.6, notching, bayoneting, ISNT rule violated, disc haemorrhage) and field loss — paracentral/Bjerrum scotoma, nasal step, then tubular field with temporal island. Normal-tension glaucoma has the same disc and field changes with IOP ≤21.
• Primary angle-closure disease: hypermetropic, shallow chamber, plateau iris; acute attack — severe pain, haloes, nausea, vomiting, vision loss, circumcorneal congestion, hazy oedematous cornea, vertically oval fixed mid-dilated pupil, very high IOP (40–70 mmHg); treated with IV acetazolamide/mannitol, topical timolol + pilocarpine 2% + steroid, then laser peripheral iridotomy in both eyes (the fellow eye is prophylactic).
• Secondary: neovascular (diabetes, CRVO — 90-day glaucoma), steroid-induced, lens-induced, uveitic, traumatic (angle recession, hyphaema), pseudoexfoliative, pigmentary, post-vitrectomy silicone oil.
• Congenital/developmental: buphthalmos, epiphora, photophobia, blepharospasm, corneal haze with Haab striae; surgical — goniotomy or trabeculotomy.
• Investigations: applanation (Goldmann — gold standard; corrected for central corneal thickness), non-contact air-puff, Schiotz indentation (obsolete but still examined); gonioscopy (Shaffer/Spaeth grading); automated perimetry; OCT RNFL and disc photography; pachymetry; diurnal variation.
• Treatment ladder: prostaglandin analogue (latanoprost — once daily, most effective, iris pigmentation and lash growth) → beta-blocker (timolol — avoid in asthma, bradycardia, heart block) → alpha-2 agonist (brimonidine) → topical/oral carbonic anhydrase inhibitor (dorzolamide, acetazolamide — paraesthesia, stones, acidosis) → pilocarpine; laser SLT/ALT for open angle, iridotomy for closed; surgery trabeculectomy with mitomycin-C, glaucoma drainage devices (Ahmed), minimally invasive options. Target IOP is a 25–30% reduction (more in advanced disease), set individually.
• Glaucoma blindness is irreversible — hence opportunistic screening of anyone over 40, all first-degree relatives of patients and every diabetic.

Cornea, conjunctiva, uvea and the red eye

• Infective keratitis: bacterial (Staph, Pseudomonas — rapidly melting), fungal (Fusarium, Aspergillus — very common in rural India after vegetative trauma: dry raised slough, feathery margins, satellites; treated with natamycin 5% or voriconazole), viral (herpes simplex dendritic ulcer — treat with acyclovir ointment, never steroid alone), Acanthamoeba (contact lens, ring infiltrate). Corneal scraping for smear (Gram, KOH) and culture before starting therapy.
• Sequelae: nebular/macular/leucomatous opacity, adherent leucoma, descemetocele, perforation, anterior staphyloma. Keratoplasty — penetrating, DALK, DSEK/DMEK; corneas come from the Eye Bank under the Transplantation of Human Organs and Tissues Act, 1994 (amended 2011); hospital cornea retrieval programmes and voluntary pledging drive supply, and India's donation still falls far short of need.
• Conjunctivitis: bacterial (mucopurulent, sticky lids), viral/adenoviral (watery, follicles, preauricular node, epidemic "Madras eye" — highly contagious, hygiene and supportive care), ophthalmia neonatorum (gonococcal day 2–4 — emergency; chlamydial day 5–14), allergic (itching, ropy discharge) and vernal keratoconjunctivitis (cobblestones, Horner-Trantas dots, common in Indian boys).
• Trachoma: Chlamydia trachomatis A/B/Ba/C — the WHO SAFE strategy (Surgery for trichiasis, Antibiotic azithromycin, Facial cleanliness, Environmental improvement) and FISTO grading. India was validated by WHO in 2024 as having eliminated trachoma as a public health problem; surveillance for trichiasis continues.
• Dry eye (aqueous-deficient and evaporative/MGD): Schirmer, TBUT, ocular surface staining; lubricants, lid hygiene, punctal plugs, cyclosporine.
• Pterygium (triangular fibrovascular growth, interpalpebral, UV-related, nasal commonest) — excision with conjunctival autograft to cut recurrence.
• Uveitis: anterior (pain, photophobia, circumcorneal congestion, ciliary flush, aqueous cells and flare, keratic precipitates, small irregular pupil, posterior synechiae) — mydriatic/cycloplegic + topical steroid plus cause-directed therapy; posterior (floaters, dimness; toxoplasmosis, tuberculosis — important in India, CMV in HIV); panuveitis. Screen for TB (Mantoux, chest X-ray), sarcoid, HLA-B27 spondyloarthropathy, Behçet, VKH, sympathetic ophthalmitis.
• The red eye — the examiner's favourite differential: see the table in the formulas section. Anything with pain, photophobia, reduced vision, corneal haze or a sluggish pupil is referred the same day; a painless red eye with normal vision is usually conjunctival.

Retina, neuro-ophthalmology, squint and trauma

• Diabetic retinopathy: the leading cause of blindness in working-age adults. Non-proliferative (microaneurysms, dot-blot haemorrhages, hard exudates, cotton-wool spots, venous beading, IRMA) graded by the 4-2-1 rule → proliferative (new vessels on disc/elsewhere, vitreous haemorrhage, tractional detachment). Diabetic macular oedema is the commonest cause of vision loss. Treatment: glycaemic/BP/lipid control, intravitreal anti-VEGF (ranibizumab, bevacizumab off-label, aflibercept) for DMO and PDR, focal laser, pan-retinal photocoagulation for proliferative disease, vitrectomy for non-clearing haemorrhage. Screening: dilated fundus or fundus photography at diagnosis in type 2, five years after onset in type 1, then yearly; and in every trimester of pregnancy. Mass screening in India now uses non-mydriatic fundus cameras with tele-reporting and AI triage.
• Hypertensive retinopathy: Keith-Wagener-Barker I–IV (attenuation → AV nipping → haemorrhages/exudates, macular star → papilloedema).
• Vascular occlusions: central retinal artery occlusion — sudden painless total loss, pale oedematous retina with cherry-red spot, boxcarring; an emergency (ocular massage, lower IOP, paracentesis) with poor prognosis; retinal survival is measured in roughly 90 minutes. CRVO — flame haemorrhages in all quadrants, tortuous veins, macular oedema; anti-VEGF ± laser, watch for neovascular glaucoma.
• Retinal detachment: rhegmatogenous (break + liquefied vitreous; floaters, photopsia, curtain, field defect, relative afferent pupillary defect, low IOP), tractional (PDR) and exudative (tumour, Coats, eclampsia). Repair — barrage laser for breaks, scleral buckle, pneumatic retinopexy, vitrectomy with gas/silicone tamponade.
• Age-related macular degeneration: dry (drusen, geographic atrophy; AREDS-type supplements) and wet (choroidal neovascularisation; intravitreal anti-VEGF). Retinitis pigmentosa — night blindness, ring scotoma, waxy disc, bone-spicule pigment, attenuated vessels, extinguished ERG.
• Retinopathy of prematurity: screen every baby <34 weeks or <2,000 g (and sicker larger babies) by 30 days of life / 3–4 weeks after birth; treated with laser or anti-VEGF. India's programme guidance makes ROP screening part of newborn care in SNCUs — a major avoidable childhood blindness.
• Childhood blindness and vitamin A: xerophthalmia sequence XN (night blindness) → X1A conjunctival xerosis → X1B Bitot spot → X2 corneal xerosis → X3A/X3B keratomalacia → XS scar → XF fundus. Treated and prevented with vitamin A 200,000 IU (100,000 IU under 1 year, 50,000 IU under 6 months) on days 0, 1 and 14; the national schedule gives 9 doses to 9 months–5 years. Retinoblastoma — leukocoria, strabismus, cat's eye reflex, RB1 gene, calcification on ultrasound/CT; never biopsy.
• Optic nerve: papilloedema (bilateral, blurred margins, enlarged blind spot, normal acuity till late), optic neuritis (young, pain on movement, RAPD, reduced colour vision, central scotoma), optic atrophy; RAPD means asymmetric optic nerve/retinal disease, not cataract.
• Squint and amblyopia: pseudosquint (epicanthus, telecanthus), concomitant (esotropia — accommodative, infantile; exotropia) and paralytic (incomitant, diplopia, abnormal head posture, nerve palsy). Tests — Hirschberg, cover-uncover and alternate cover, prism bar, Maddox rod/wing, synoptophore, forced duction. Amblyopia (reduced vision without organic cause — strabismic, anisometropic, deprivation) must be treated before about 8 years: full refractive correction, then occlusion or atropine penalisation of the better eye; surgery for residual deviation.
• Ocular trauma: closed globe (corneal abrasion, hyphaema, traumatic iritis, Berlin oedema, angle recession) and open globe (laceration, intraocular foreign body — never pad an open globe, shield it, give tetanus prophylaxis and systemic antibiotics, image with CT, refer the same day). Chemical burn: immediate copious irrigation for 15–30 minutes before anything else — alkali is worse than acid. Siderosis (iron) and chalcosis (copper) from retained foreign bodies; sympathetic ophthalmitis in the fellow eye after penetrating injury.
• Community eye care — NPCBVI (National Programme for Control of Blindness and Visual Impairment, launched 1976 as NPCB, renamed 2017): free cataract surgery through government and NGO/private partners with per-case grant-in-aid, school eye screening with free spectacles, Vision Centres at PHC level, District Blindness Control Societies, eye banks, diabetic retinopathy and ROP screening, and a national register. Delivery is tiered — Vision Centre (PHC, optometrist, refraction) → Service Centre (CHC) → District Hospital → Regional Institute of Ophthalmology. The old *Vision 2020: Right to Sight* goals have been carried into the current programme and the WHO *World Report on Vision* integrated people-centred eye care approach; exact grant rates change by year and should be read off the current NPCBVI guidelines rather than quoted from memory.

Key points

• Total eye power — about +60 D; cornea contributes ~43 D, lens ~17 D; axial length ~24 mm.
• Myopia / hypermetropia — image before / behind the retina; concave (−) / convex (+) lens corrects.
• Astigmatism — meridional focus difference; cylindrical or toric correction; irregular needs RGP lenses.
• Presbyopia — loss of accommodation with age; near add +1.00 D at 40 rising to about +3.00 D by 60.
• Snellen fraction — test distance / distance a normal eye reads that line; 6/60 is the top letter at 6 m.
• Blindness in India (programme) — presenting acuity worse than 3/60 in the better eye since the 2017 revision (earlier <6/60).
• RPwD Act 2016 — blindness ≤3/60 best-corrected or field ≤10°; low vision 6/18–3/60 or field 10–40°.
• Commonest cause of blindness in India — cataract, followed by uncorrected refractive error; both avoidable.
• Cataract surgery of choice — phacoemulsification with foldable IOL; SICS where cataracts are hard or volume and cost dominate.
• Endophthalmitis — pain with falling vision 2–7 days after surgery, hypopyon; vitreous tap plus intravitreal vancomycin and ceftazidime.
• Normal IOP — 10–21 mmHg; Goldmann applanation is the gold standard, corrected for corneal thickness.
• POAG — painless, bilateral, cupping (C:D >0.6, ISNT violated) with Bjerrum scotoma and nasal step; prostaglandin analogue first line.
• Acute angle closure — painful red eye, haloes, hazy cornea, vertically oval fixed pupil, IOP 40–70; iridotomy to both eyes.
• Fungal keratitis — dry slough, feathery margins, satellite lesions after vegetative trauma; natamycin 5%; no steroid.
• Trachoma — SAFE strategy; India validated by WHO as having eliminated it as a public health problem in 2024.
• Diabetic retinopathy — 4-2-1 rule marks severe NPDR; anti-VEGF for macular oedema, PRP for proliferative disease.
• Vitamin A — 200,000 IU on days 0, 1, 14 for xerophthalmia; Bitot spot is X1B; keratomalacia blinds within days.
• Amblyopia — treatable only in the plastic period (up to about 8 years) with correction plus occlusion/penalisation.
• Chemical injury — irrigate first, for 15–30 minutes, before recording vision; alkali penetrates deeper than acid.

Formulas and examples

Example 1 — acuity, logMAR and the Snellen fraction. A patient reads the 18 m line at 6 m with the right eye and only the 60 m line with the left.

• RE = 6/18 → decimal 0.333 → logMAR = log₁₀(18/6) = log₁₀3 = 0.48.
• LE = 6/60 → decimal 0.1 → logMAR = log₁₀(10) = 1.0.
• Better eye presenting acuity 6/18 → moderate visual impairment is excluded (6/18 is the boundary; worse than 6/18 is needed), so the patient is neither blind (needs worse than 3/60) nor low vision under RPwD. With pinhole the RE improves to 6/6 → the loss is refractive, not organic.

Example 2 — retinoscopy to spectacle prescription. Streak retinoscopy at 1 m gives, for the right eye, +3.00 D along 180° and +1.00 D along 90°.

• Subtract the working distance 1/1 m = 1.00 D from both: +2.00 D at 180°, 0.00 D at 90°.
• Write as sphere + minus cylinder: more plus meridian as sphere = +2.00 DS, cylinder = 0.00 − (+2.00) = −2.00 D with its axis along the meridian of greatest plus power, 180°, because a minus cylinder has no power along its own axis, i.e. +2.00 / −2.00 × 180.
• Spherical equivalent = +2.00 + ½(−2.00) = +1.00 D. Being a 6-year-old, the refraction is repeated under cycloplegia before prescribing.

Example 3 — presbyopic near add. A 48-year-old emmetrope has a near point of 50 cm and needs to read at 33 cm; amplitude of accommodation measured as 2.00 D.

• Power needed for 33 cm = 1/0.33 = 3.00 D.
• Usable accommodation = half the amplitude = 1.00 D (the rest is reserve).
• Near add = 3.00 − 1.00 = +2.00 D → prescription: distance plano, add +2.00 D — a little more than the +1.50 D the age-based table suggests at 48, because this patient's amplitude of accommodation is below average for the age.

Example 4 — IOL power by SRK II. A cataractous eye: keratometry K₁ 43.50 D, K₂ 44.50 D, axial length 23.2 mm, A-constant 118.4 (for an in-the-bag posterior-chamber IOL).

• Mean K = (43.50 + 44.50)/2 = 44.00 D.
• P = 118.4 − 0.9 × 44.00 − 2.5 × 23.2 = 118.4 − 39.6 − 58.0 = 20.8 D → implant the nearest available power, about +21.0 D, aiming for slight myopia (−0.25 to −0.50 D) if the patient wants useful near vision. Modern practice would cross-check with SRK/T or Barrett, since SRK II loses accuracy below 22 mm and above 24.5 mm.

Example 5 — outflow facility from the Goldmann equation. Aqueous formation 2.4 µL/min, uveoscleral outflow 0.4 µL/min, IOP 30 mmHg, episcleral venous pressure 10 mmHg.

• Trabecular flow = 2.4 − 0.4 = 2.0 µL/min; C = 2.0 / (30 − 10) = 0.10 µL/min/mmHg — well below the normal ~0.25, i.e. obstructed trabecular outflow.
• If a prostaglandin analogue doubles uveoscleral outflow to 0.8 µL/min with C unchanged, the new IOP = 10 + (2.4 − 0.8)/0.10 = 10 + 16 = 26 mmHg, a 13% fall — explaining why a single drug often cannot reach a 30% target and combinations are needed.

The red eye — differential diagnosis

Visual field defects and the lesion

Where it is used

• Government service: district hospital and CHC ophthalmology, NPCBVI district programme management (cataract targets, camps, school screening, Vision Centres), disability certification boards under the RPwD Act 2016, and medical fitness/colour-vision certification for railways, defence and transport licensing.
• High-volume eye care and NGOs: Aravind Eye Hospitals (Madurai), LV Prasad Eye Institute (Hyderabad), Sankara Nethralaya (Chennai), Dr Shroff's, Sitapur Eye Hospital, Lions and Rotary camps — SICS/phaco surgeons, optometrists, counsellors, eye-bank technicians and community eye-health managers.
• Primary and school health: teacher-led vision screening, refraction and free spectacles under NPCBVI and Rashtriya Bal Swasthya Karyakram, Anganwadi vitamin A rounds, ROP screening in SNCUs.
• Chronic disease clinics: annual dilated fundus or fundus-camera screening of every diabetic (NP-NCD clinics), tele-ophthalmology and AI-assisted retinopathy grading hubs.
• Industry: IOL and viscoelastic manufacture (Aurolab, Appasamy, Biotech Vision Care), ophthalmic equipment and diagnostics, spectacle lens retail (Lenskart, Titan Eyeplus), pharmaceutical ophthalmology (Sun, Cipla, Entod, FDC) and clinical research in anti-VEGF and myopia control.
• Academia and PG training: MS/DNB ophthalmology, optometry (B.Optom) teaching, fellowships in cornea, retina, glaucoma, paediatric ophthalmology and community ophthalmology.

Interview questions

• Q: How do you record vision when the patient cannot see the top line of the Snellen chart at 6 m? A: Walk the patient closer and record the distance (3/60, 1/60), then counting fingers, hand movements, perception and projection of light, and finally no perception of light.
• Q: What is India's current definition of blindness for the national programme? A: Presenting visual acuity worse than 3/60 in the better eye, adopted in 2017 in place of the earlier worse-than-6/60 criterion, so that data match the WHO definition.
• Q: Why is pinhole acuity important? A: Improvement with a pinhole indicates a refractive or media cause that correction can fix; no improvement points to organic macular or optic nerve disease.
• Q: SICS or phacoemulsification for a rural cataract camp? A: SICS — sutureless, no phaco machine or expensive consumables, handles hard brunescent cataracts quickly and gives comparable best-corrected outcomes, though phaco recovers faster and gives better early uncorrected vision.
• Q: A patient has pain and falling vision three days after cataract surgery. What do you do? A: Treat it as acute endophthalmitis — examine for hypopyon and vitritis, take a vitreous tap for culture and give intravitreal vancomycin plus ceftazidime, with immediate vitrectomy if vision is down to perception of light only (Endophthalmitis Vitrectomy Study), tap-and-inject at hand movements or better.
• Q: Why is glaucoma called a silent thief of sight? A: Open-angle glaucoma destroys peripheral retinal nerve fibres painlessly and the fellow eye fills the defect, so patients present only when the field is tubular and the loss is irreversible.
• Q: Which drop would you avoid in an asthmatic glaucoma patient, and what would you use instead? A: Avoid timolol and other beta-blockers; use a prostaglandin analogue such as latanoprost, or dorzolamide/brimonidine.
• Q: Why must the fellow eye be lasered after an acute angle-closure attack? A: It has the same anatomically narrow angle and a high risk of an attack, so prophylactic peripheral iridotomy is standard.
• Q: A farmer has a corneal ulcer with feathery margins and satellite lesions after injury with a paddy stalk. Diagnosis and first step? A: Fungal keratitis — scrape for KOH mount and culture and start topical natamycin 5%; steroids are contraindicated.
• Q: How do you screen a newly diagnosed type 2 diabetic for retinopathy? A: Dilated fundus examination or fundus photography at diagnosis and then annually, more often with any retinopathy, and in every trimester of pregnancy.
• Q: What is the first thing you do for an alkali splash in the eye? A: Irrigate immediately and copiously with water or saline for 15–30 minutes, before recording vision or history, and check that the pH has returned to normal.
• Q: Why must a squinting child be refracted under cycloplegia? A: Active accommodation in children masks hypermetropia; cycloplegia reveals the full error, and correcting it alone may abolish an accommodative esotropia.
• Q: What does a relative afferent pupillary defect tell you in a patient with sudden painless vision loss? A: Asymmetric optic nerve or extensive retinal disease — for example optic neuritis, CRAO or a large detachment; a cataract, however dense, does not cause an RAPD.

Common mistakes

• Writing the Snellen fraction upside down (60/6) or quoting "6/6 vision" as proof that the eye is normal — acuity tests only the fovea, not fields, colour or the disc.
• Quoting the old "worse than 6/60" definition of blindness for India without noting the 2017 revision to worse than 3/60, and mixing the programme definition with the RPwD Act's best-corrected criteria.
• Forgetting to subtract the working distance in retinoscopy, or prescribing a child's refraction without cycloplegia.
• Giving a topical steroid for a red eye with a corneal lesion — it converts a dendritic or fungal ulcer into a perforation; steroids are also the commonest cause of drug-induced glaucoma.
• Dilating an eye with a shallow anterior chamber without gonioscopy, or dilating before the pupillary reactions and RAPD are recorded.
• Calling a painless, non-congested loss of vision "conjunctivitis" — and conversely padding an open globe injury instead of shielding it.
• Prescribing the full amplitude of accommodation as the near add instead of half, and ignoring vertex distance in high powers.
• Assuming a cataract explains an RAPD or a field defect, so missing coexisting glaucoma, diabetic maculopathy or an optic neuropathy before surgery.
• Quoting NPCBVI grant-in-aid rates, cataract surgical rates or survey prevalences from memory — they are revised periodically and should be read off the current guidelines or survey report.

Related topics

Otorhinolaryngology (ENT) essentials · National health programmes in India · Non-communicable diseases: epidemiology and prevention · Public health nutrition: ICDS, POSHAN Abhiyaan and mid-day meals · Communicable disease epidemiology and outbreak investigation · Epidemiology: principles, measures and study designs