Retina Rounds in Unit 1: Pearls, Macular Numbers and Occlusions
Last updated: October 2026
Teaching points from retina rounds in Unit 1 (Prof. Garg's fundology sessions), tidied up and checked against current practice. Where practice has changed since the rounds, the update is noted.
Pearls from the rounds
| Pearl | Explanation and current note |
|---|---|
| Heredofamilial macular dystrophy, not "degeneration" | Bilateral, symmetrical, in young patients: dull foveal reflex with mottled pigment and a silvery sheen. Look for family history and order OCT, autofluorescence and ERG |
| Young patient with a vascular occlusion | Always look for vitreous cells: inflammation (vasculitis, Behçet, sarcoid, TB) must be excluded before calling it a simple occlusion |
| Shafer sign (tobacco dust) is less reliable in some eyes | Pigment in the anterior vitreous strongly suggests a retinal break, but can also follow uveitis, trauma, intraocular surgery or vitreous haemorrhage |
| Cylinder and high spheres | Above about 4 D of sphere, small cylinders add little to blur; a 1 D cylinder still matters and should be corrected |
| High risk of RD before cataract surgery | Treat symptomatic breaks and high-risk lattice (fellow-eye RD, high myopia, Stickler) with laser before surgery |
| PRP and macular oedema | PRP can worsen DME. Old rule: focal laser before PRP. Current practice: treat centre-involving DME with anti-VEGF first; anti-VEGF also controls PDR (Protocol S), with PRP as needed |
| Neovascularisation of the angle | NVA can occur without visible NVI, especially after CRVO, so do undilated gonioscopy in every ischaemic occlusion |
| Signs of a long-standing RD | Pigmented demarcation lines, intraretinal macrocysts, retinal thinning and subretinal bands |
Macular anatomy numbers
| Structure | Size | Notes |
|---|---|---|
| Macula (area centralis) | About 5.5 mm diameter | Histologically: more than one layer of ganglion cells; clinically: xanthophyll |
| Fovea | About 1.5 mm diameter | Centre lies about 4 mm temporal and 0.8 mm inferior to the disc centre |
| Foveola | About 0.35 mm diameter | Only cones, no ganglion cells |
| Foveal avascular zone | About 0.4–0.5 mm diameter | Larger in diabetic maculopathy |
Vascular occlusion numbers
| Condition | Key facts |
|---|---|
| CRAO | Emboli are found in about 20%; the rest are thrombotic, vasculitic or traumatic. Exclude giant cell arteritis in everyone over 50. Iris neovascularisation in about 15–20%. Refer via the stroke pathway |
| BRAO | About 90% embolic; also inflammatory causes (toxoplasmosis, acute retinal necrosis). NVI is very rare |
| Boxcarring | Segmentation of the blood column in arteries and veins distal to an arterial block |
| BRVO | Risk factors: hypertension, cardiovascular disease, raised BMI, glaucoma. Fellow eye affected in about 10%. Ischaemic if more than 5 disc areas of non-perfusion; neovascularisation in about 40% of ischaemic BRVO, and about 60% of those bleed |
| CRVO | Risk factors: hypertension, diabetes, glaucoma. Ischaemic if 10 or more disc areas of non-perfusion (CVOS), with poor vision, RAPD and extensive haemorrhage |
| Endophthalmitis after intravitreal triamcinolone | Reported up to about 1.4%, including sterile pseudo-endophthalmitis; about 0.6% when those are excluded (older series) |
Related: Retina hub, Retinal artery occlusion, Retinal layers and OCT made easy.
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