Retina, vitreous, and choroid
Retina questions are the largest single source of marks and are usually descriptions rather than images: sudden painless visual loss, a diabetic with new haemorrhage, or an abnormal disc. Learn the vascular and degenerative patterns and the treatment thresholds.
Diabetic retinopathy
Non-proliferative grading follows the ETDRS scale: microaneurysms, haemorrhages, hard exudates, cotton wool spots, venous beading and intraretinal microvascular abnormalities. Severe non-proliferative disease follows the 4-2-1 rule. Proliferative disease shows neovascularisation at the disc or elsewhere, with vitreous haemorrhage and tractional detachment. Diabetic macular oedema is the commonest cause of vision loss and is treated with anti-VEGF, with focal laser for non-central disease; proliferative disease is treated with panretinal photocoagulation or anti-VEGF.
Vascular and degenerative disease
Retinal vein occlusion gives sector haemorrhages and macular oedema; check blood pressure and glucose. Central retinal artery occlusion shows a pale retina with a cherry-red spot and is a stroke equivalent requiring carotid and cardiac assessment. Age-related macular degeneration is dry with drusen and geographic atrophy, or wet with a choroidal neovascular membrane treated with anti-VEGF.
Detachment and the vitreous
Rhegmatogenous detachment follows a tear, with photopsia, floaters and a field defect; look for pigment in the anterior vitreous, lattice degeneration, and treat tears with laser or cryotherapy. Tractional detachment in diabetes shows a taut retina without a tear; exudative detachment shows shifting fluid. Macular hole and epiretinal membrane are vitreomacular interface diseases treated by vitrectomy.
Worked example
A 60-year-old has a sudden curtain across the vision, floaters, and a horseshoe tear with subretinal fluid. Reasoning: this is rhegmatogenous detachment from a symptomatic tear. The presence of a tear rather than a taut retina separates it from tractional detachment, the fellow eye needs a peripheral examination, and surgery is required rather than observation.
Traps
Treating central retinal artery occlusion as an eye problem only; missing a tear in the fellow eye; confusing dry and wet AMD management; failing to document screening intervals in diabetes.