Master Ophthalmology
for PLAB 1

What the PLAB 1 Tests in Ophthalmology

PLAB 1 tests your ability to manage common ophthalmic presentations in a UK emergency or GP setting. You must differentiate sight-threatening emergencies (e.g., acute angle closure glaucoma, central retinal artery occlusion, giant cell arteritis) from benign conditions (e.g., conjunctivitis, stye, dry eye). Questions focus on immediate triage, appropriate first-line investigations (e.g., slit-lamp, fluorescein staining, intraocular pressure measurement), and correct initial management (e.g., topical antibiotics, acetazolamide, urgent referral). You are expected to know red flags (e.g., sudden vision loss, painful red eye, relative afferent pupillary defect), key drug classes and their contraindications (e.g., topical beta-blockers in asthma), and when to use systemic steroids or antiviral therapy. Basic interpretation of fundoscopy findings (e.g., papilloedema, diabetic retinopathy) and knowledge of driving standards (DVLA rules) are also tested.

High-Yield Concepts

• Acute Angle Closure Glaucoma: Presents with severe eye pain, headache, nausea/vomiting, blurred vision, halos around lights, fixed mid-dilated pupil, cloudy cornea, and raised IOP (>40 mmHg). First-line: immediate referral to ophthalmology; give acetazolamide 500 mg IV or PO, topical pilocarpine 2% (if IOP <40 mmHg), and topical beta-blocker (e.g., timolol 0.5%). Avoid anticholinergics and mydriatics.
• Giant Cell Arteritis (Temporal Arteritis): Suspect in patients >50 years with new-onset headache, scalp tenderness, jaw claudication, and sudden vision loss (often anterior ischaemic optic neuropathy). ESR is typically >50 mm/hr, CRP elevated. Immediate high-dose prednisolone (60–100 mg PO or IV) to prevent contralateral blindness; urgent temporal artery biopsy within 1 week.
• Central Retinal Artery Occlusion (CRAO): Sudden, painless, profound vision loss (light perception or worse) with relative afferent pupillary defect (RAPD). Fundoscopy shows retinal whitening (ischaemic oedema) and cherry-red spot at fovea. Emergency: refer immediately for possible thrombolysis (within 6 hours) or ocular massage, anterior chamber paracentesis, and acetazolamide to lower IOP. Exclude giant cell arteritis.
• Orbital Cellulitis vs Preseptal Cellulitis: Preseptal: eyelid oedema/erythema, no proptosis, no pain on eye movement, normal vision. Orbital: proptosis, restricted extraocular movements, pain on movement, reduced vision, RAPD. Orbital cellulitis is an emergency: IV antibiotics (e.g., co-amoxiclav or ceftriaxone + metronidazole) and urgent CT orbits; may require surgical drainage.
• Diabetic Retinopathy Screening: Annual digital retinal photography for all diabetics ≥12 years. Refer to ophthalmology if: any pre-proliferative changes (cotton wool spots, venous beading), proliferative retinopathy (new vessels, vitreous haemorrhage), or clinically significant macular oedema (hard exudates within 500 μm of fovea). Laser photocoagulation or anti-VEGF (ranibizumab) for macular oedema.
• Herpes Simplex Keratitis: Presents with unilateral red eye, photophobia, tearing, and dendritic ulcer on fluorescein staining (branched pattern with terminal bulbs). First-line: topical aciclovir 3% ointment 5 times daily for 10–14 days. Do NOT use topical steroids (can worsen infection and cause corneal perforation).
• Retinal Detachment: Symptoms: sudden onset of floaters, flashing lights (photopsia), and a curtain-like shadow over vision. Signs: RAPD, low IOP, visible retinal tear on fundoscopy. Urgent same-day referral to ophthalmology; treatment: pneumatic retinopexy, scleral buckle, or vitrectomy. Advise patient to avoid eye rubbing and heavy lifting.
• Driving Standards (DVLA) – Vision: Group 1 (car/motorcycle): visual acuity ≥6/12 (Snellen) with both eyes open (or better eye ≥6/12, worse eye ≥6/60), and horizontal visual field ≥120° (no significant defect within 20° of fixation). Group 2 (lorry/bus): stricter: acuity ≥6/7.5 in better eye, ≥6/60 in worse, field ≥160°. Must report any visual impairment affecting driving.

Common Traps in Ophthalmology Questions

• Confusing acute angle closure glaucoma with conjunctivitis: the latter has no severe pain, no fixed pupil, and normal IOP.
• Using topical steroids for a red eye without fluorescein staining: can worsen herpes simplex keratitis or fungal infection.
• Assuming all sudden vision loss is retinal detachment: think of CRAO, optic neuritis, or vitreous haemorrhage (especially in diabetics).
• Forgetting to check for RAPD in any unilateral vision loss: its presence indicates optic nerve or retinal disease, not media opacity.
• Treating giant cell arteritis only after biopsy result: start steroids immediately if clinical suspicion is high; delay risks blindness.
• Missing orbital cellulitis because you only see eyelid swelling: always check for proptosis, pain on eye movement, and vision changes.

How to Revise Ophthalmology for the PLAB 1

Prioritise the painful red eye and sudden vision loss algorithms. For each condition, memorise the classic triad of symptoms, the key physical exam finding (e.g., cherry-red spot, dendritic ulcer, fixed dilated pupil), and the single most critical first step (e.g., acetazolamide, IV steroids, urgent referral). Questions often present a clinical vignette with a time-critical decision; practise distinguishing between emergency (e.g., CRAO, giant cell arteritis, orbital cellulitis) and non-emergency (e.g., simple conjunctivitis, dry eye). Also review DVLA vision standards and diabetic retinopathy referral criteria. Use flashcards for drug doses and contraindications (e.g., topical beta-blockers in asthma, steroids in herpes).

Practise it: MedLumen has 50 Ophthalmology questions for the PLAB 1, each with a full explanation and references.