Diabetic retinopathy
Chronic hyperglycaemia damages retinal capillaries, driving a progression from microvascular leakage to ischaemia to pathological new vessel growth, which is why screening and staging by the underlying vascular damage, not symptoms, determines when to treat.
In a nutshell
Chronic hyperglycaemia damages retinal capillary walls and pericytes, causing leakage (microaneurysms, haemorrhages, exudates) and eventually ischaemia. Ischaemic retina releases VEGF, driving fragile new vessel growth that bleeds or detaches the retina. The entire staging system tracks this single escalating mechanism.
Classic presentation
A patient with longstanding diabetes, asymptomatic and picked up on routine screening with microaneurysms and exudates, or presenting with gradual central blurring from macular oedema or sudden visual loss from vitreous haemorrhage.
Key points
- Early retinopathy is asymptomatic: screening, not symptoms, is how it is caught, because peripheral capillary damage does not affect vision until late.
- Ischaemia drives VEGF release, and VEGF drives neovascularisation: this single link explains why anti-VEGF and pan-retinal photocoagulation are the two mainstay treatments.
- Macular oedema and proliferative disease are two separate routes to visual loss and can occur independently at any retinopathy stage.
- Pan-retinal photocoagulation deliberately sacrifices ischaemic peripheral retina, and some peripheral field, to reduce VEGF drive and protect central vision.
- Glycaemic, blood pressure and lipid control slow the primary capillary damage that underlies every later complication.
First-line investigation
Digital retinal photography as part of routine diabetic eye screening: it detects asymptomatic microvascular changes before they threaten vision.
First-line management
Optimise glycaemic control, blood pressure and lipids to slow capillary damage, with anti-VEGF for macular oedema or pan-retinal photocoagulation for proliferative disease as needed.
Exam traps
- A patient with normal central vision can still have sight-threatening proliferative retinopathy: visual acuity does not reliably reflect retinopathy stage.
- Sudden painless visual loss in a diabetic patient is vitreous haemorrhage until proven otherwise, not a stroke or simple blurred vision.
- Very rapid, aggressive glycaemic correction in longstanding poor control can transiently worsen retinopathy, so the trajectory of change matters clinically, not just the target.
Educational content pending clinical review. Not medical advice.