Master Ophthalmology
for MRCP Part 1

What the MRCP Part 1 Tests in Ophthalmology

MRCP Part 1 Ophthalmology tests the recognition and initial management of sight- and life-threatening conditions, including acute angle closure glaucoma, central retinal artery occlusion, giant cell arteritis, and retinal detachment. Candidates must differentiate benign from urgent presentations (e.g., subconjunctival haemorrhage vs. hyphaema), interpret fundoscopic findings (papilloedema, Roth spots, cotton wool spots, cherry red spot), and know first-line treatments (e.g., acetazolamide for acute glaucoma, intravenous methylprednisolone for optic neuritis). Drug-induced ocular side effects (e.g., ethambutol optic neuropathy, hydroxychloroquine retinopathy, topiramate-induced angle closure) and systemic disease ocular manifestations (diabetic retinopathy staging, hypertensive retinopathy grades, thyroid eye disease) are heavily tested. The emphasis is on clinical decision-making: which condition requires immediate referral, which drug to stop, and which investigation (e.g., fluorescein angiography, OCT, urgent ESR/CRP) is diagnostic.

High-Yield Concepts

• Acute Angle Closure Glaucoma: Presents with painful red eye, blurred vision, halos around lights, fixed mid-dilated pupil, and raised intraocular pressure (>40 mmHg). First-line: immediate topical pilocarpine 2%, intravenous acetazolamide 500 mg, and topical beta-blocker (timolol 0.5%). Definitive treatment: laser peripheral iridotomy. Do not dilate the pupil.
• Giant Cell Arteritis (Temporal Arteritis): Causes anterior ischaemic optic neuropathy (AION) with sudden painless vision loss, headache, scalp tenderness, jaw claudication, and elevated ESR (>50 mm/hr) and CRP. Urgent high-dose prednisolone (60-100 mg daily) and temporal artery biopsy within 1 week. Delayed treatment risks bilateral blindness.
• Diabetic Retinopathy: Referral Criteria: Refer urgently if: new vessels (proliferative), vitreous haemorrhage, or rubeosis iridis. Refer non-urgently if: pre-proliferative (cotton wool spots, venous beading, intraretinal microvascular abnormalities), or clinically significant macular oedema (hard exudates within 500 μm of fovea). Screening uses digital fundus photography.
• Central Retinal Artery Occlusion: Sudden, painless, severe vision loss with relative afferent pupillary defect (RAPD) and cherry red spot at fovea (pale retina). Immediate management: ocular massage, intravenous acetazolamide, and reduction of intraocular pressure. Screen for giant cell arteritis, carotid stenosis, and embolic source (e.g., atrial fibrillation).
• Optic Neuritis: Typically young adults (20-40 years), unilateral painful eye movement, reduced colour vision (desaturation of red), central scotoma, and RAPD. MRI brain to assess for demyelinating lesions. Treatment: high-dose intravenous methylprednisolone (1 g daily for 3 days) accelerates recovery but does not alter long-term multiple sclerosis risk.
• Hydroxychloroquine Retinopathy: Risk factors: cumulative dose >5 g/kg, duration >5 years, renal impairment, concurrent tamoxifen. Screening: baseline and annual retinal examination with spectral-domain OCT and visual fields (10-2). Bull's eye maculopathy is late; early changes are parafoveal photoreceptor loss. Stop drug if toxicity detected.
• Horner's Syndrome: Triad: ptosis, miosis, anhidrosis (ipsilateral). Distinguish preganglionic (e.g., Pancoast tumour, carotid dissection) from postganglionic (e.g., cavernous sinus lesion). Pharmacological testing: apraclonidine 0.5% reverses anisocoria in Horner's (dilates affected pupil). Urgent imaging of neck and chest if new onset.
• Retinal Detachment: Presents with sudden flashes (photopsia), floaters (often 'curtain' or 'shadow'), and progressive visual field loss. On fundoscopy: elevated retina with corrugated appearance. Urgent referral for vitreoretinal surgery (pneumatic retinopexy, scleral buckle, or vitrectomy). Risk factors: high myopia, aphakia, trauma, lattice degeneration.

Common Traps in Ophthalmology Questions

• Confusing acute angle closure glaucoma with anterior uveitis: both have red eye and photophobia, but uveitis has a small, irregular pupil and normal or low IOP, whereas glaucoma has a fixed mid-dilated pupil and very high IOP.
• Assuming all optic disc swelling is papilloedema: must distinguish true papilloedema (raised ICP) from pseudopapilloedema (drusen) using ultrasound or OCT; also consider AION, optic neuritis, and malignant hypertension.
• Forgetting that topiramate can cause acute angle closure glaucoma: patients on this drug for migraine or epilepsy presenting with red painful eye should have IOP checked immediately.
• Missing giant cell arteritis in elderly patients with transient vision loss (amaurosis fugax) or diplopia: always check ESR/CRP before attributing to carotid disease alone.
• Thinking that ethambutol optic neuropathy is reversible at any stage: early detection is critical; once vision loss is advanced, recovery is poor even after drug cessation.

How to Revise Ophthalmology for the MRCP Part 1

Prioritise memorising the ocular manifestations of systemic diseases (diabetes, hypertension, giant cell arteritis, sarcoidosis, syphilis, HIV) and the classic triad for each emergency: acute glaucoma (pain, red eye, fixed pupil), retinal artery occlusion (painless vision loss, RAPD, cherry red spot), and optic neuritis (pain on eye movement, reduced colour vision, central scotoma). Practice interpreting fundus photos and visual field defects (bitemporal hemianopia from chiasmal lesion, homonymous hemianopia from occipital stroke). Focus on drug side effects (ethambutol, hydroxychloroquine, amiodarone, tamoxifen, vigabatrin, topiramate) and which to stop. Questions often present a brief clinical scenario and ask for the most likely diagnosis, next step in management, or drug to avoid. Use flashcards for criteria (e.g., diabetic retinopathy staging, hypertensive retinopathy grades) and mnemonics for cranial nerve palsies (e.g., 'down and out' for CN III palsy).

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