Key Facts

Diabetic retinopathy is a microvascular complication of diabetes. Prevention through glycaemic and blood pressure control, early detection through screening, and timely treatment are the pillars of management.

Epidemiology

• ~4.9 million people with diabetes in the UK; ~1.4 million have some retinopathy
• Leading cause of blindness in 16-64 year olds
• Risk factors: duration of diabetes (most important), poor glycaemic control, hypertension, dyslipidaemia, pregnancy, nephropathy

Aetiology

• Chronic hyperglycaemia → microvascular damage to retinal capillaries
• Duration of diabetes is the strongest risk factor
• HbA1c is the most important modifiable factor (DCCT/UKPDS trials)

Pathophysiology

• Hyperglycaemia → polyol pathway activation, AGE formation, PKC activation → pericyte loss → endothelial dysfunction → capillary closure → retinal ischaemia
• Ischaemia → VEGF production → neovascularisation (proliferative)
• Increased capillary permeability → macular oedema (fluid and lipid leakage)
• New vessels are fragile → vitreous haemorrhage; fibrosis → tractional retinal detachment

Background Retinopathy (R1)

• Usually asymptomatic
• Microaneurysms (earliest sign; red dots)
• Dot and blot haemorrhages
• Hard exudates (lipid deposits — yellow waxy deposits)

Pre-proliferative (R2)

• Cotton wool spots (retinal nerve fibre layer infarcts)
• Venous beading and looping
• IRMA (intraretinal microvascular abnormalities)
• Deep dark blot haemorrhages
• Indicates worsening ischaemia

Proliferative (R3)

• New vessels on disc (NVD) or elsewhere (NVE)
• Pre-retinal or vitreous haemorrhage (sudden visual loss)
• Tractional retinal detachment (if fibrovascular proliferation)
• Rubeosis iridis (new vessels on iris) → neovascular glaucoma

Diabetic Maculopathy (M1)

• Reduced central visual acuity
• Hard exudates within 1 disc diameter of fovea
• Clinically significant macular oedema (CSMO)

Red Flags

• Sudden visual loss (vitreous haemorrhage, retinal detachment)
• New vessels on examination
• Rubeosis (new iris vessels — neovascular glaucoma imminent)
• Macular involvement (central visual threat)

Bedside

• Visual acuity (Snellen)
• Dilated fundoscopy (slit lamp biomicroscopy)
• NHS DESP screening photograph

Bloods

• HbA1c (glycaemic control)
• BP measurement (target <140/80)
• Lipid profile
• U&Es (nephropathy associated with worse retinopathy)

Imaging

• OCT: gold standard for macular oedema assessment (fluid, thickness)
• Fundus fluorescein angiography (FFA): identifies ischaemia, leakage, neovascularisation
• Wide-field retinal imaging: captures peripheral retina

Special Tests

• Grading of retinopathy (NSC classification: R0-R3, M0-M1)
• 7-field stereo photography (research gold standard)

Non-pharmacological

• Glycaemic control: HbA1c <53 mmol/mol (7%); DCCT: 76% reduction in retinopathy progression with intensive control
• Blood pressure control: target <140/80 (UKPDS: 34% reduction with tight BP control)
• Lipid management: statins as per cardiovascular risk
• Annual screening: NHS DESP; more frequent if higher-grade retinopathy
• Smoking cessation

Pharmacological

• Diabetic macular oedema (centre-involving):
  • Anti-VEGF intravitreal injections: aflibercept 2mg or ranibizumab 0.5mg (NICE TA274/TA346)
  • Loading: 3-6 monthly injections then PRN/treat and extend
• Non-centre-involving macular oedema: macular laser photocoagulation
• Intravitreal steroid implant (dexamethasone — Ozurdex; fluocinolone — Iluvien): for persistent DMO, especially pseudophakic patients

Surgical/Interventional

• Pan-retinal photocoagulation (PRP): for proliferative retinopathy
  • Burns peripheral retina → reduces ischaemic drive → regression of new vessels
  • Side effects: reduced peripheral vision, reduced night vision
• Macular laser: focal/grid laser for non-centre-involving DMO
• Vitrectomy: for non-clearing vitreous haemorrhage, tractional retinal detachment involving macula, epiretinal membrane

Referral Criteria

• R1 (background): annual screening
• R2 (pre-proliferative): ophthalmology referral within 13 weeks
• R3 (proliferative): urgent ophthalmology referral within 2 weeks
• M1 (maculopathy): ophthalmology referral within 13 weeks
• Sudden visual loss: emergency ophthalmology referral

• Background retinopathy: not sight-threatening; requires monitoring and risk factor optimisation
• Proliferative retinopathy: sight-threatening without treatment; PRP prevents severe visual loss in >95% (DRS trial)
• Diabetic macular oedema: anti-VEGF improves visual acuity (DRCR.net Protocol T: aflibercept superior for worse baseline VA)
• Tight glycaemic control: DCCT showed 76% reduction in retinopathy development; UKPDS confirmed in type 2
• Screening: NHS DESP has significantly reduced diabetes-related blindness in the UK

NHS Diabetic Eye Screening Classification

Key Trials