Diabetic Retinopathy — Stages, Laser Treatment, Anti-VEGF & Screening Guide — Symptoms, Causes & Treatment | MyMedicPlus

Diabetic retinopathy (DR) is a progressive microvascular complication of both Type 1 and Type 2 diabetes mellitus, caused by chronic hyperglycaemia damaging the small blood vessels of the retina. It is the leading cause of preventable blindness in working-age adults globally, affecting approximately 35% of the 537 million people with diabetes worldwide. DR exists on a spectrum of severity — from mild non-proliferative DR (NPDR, characterised by microaneurysms) through moderate and severe NPDR to proliferative DR (PDR, the most advanced stage — with fragile new blood vessel growth on the retina and vitreous, at risk of haemorrhage and tractional retinal detachment). Diabetic macular oedema (DMO) — swelling of the central retina (macula) — can occur at any stage and is the most common cause of vision loss in DR. Both preventable by good glycaemic control and detectable at pre-visual-loss stages by annual screening — making DR a model condition for secondary prevention.

Chronic hyperglycaemia is the fundamental cause, initiating a cascade of retinal microvascular damage: polyol pathway overactivity (sorbitol accumulation), advanced glycation end-products (AGEs), protein kinase C activation, and increased oxidative stress all damage pericytes (the supporting cells of retinal capillaries), leading to capillary wall weakness, microaneurysm formation, basement membrane thickening, and eventually capillary closure (ischaemia). Ischaemia drives upregulation of vascular endothelial growth factor (VEGF) — the key mediator of pathological neovascularisation in PDR and increased permeability in DMO. Risk factors: duration of diabetes (the strongest predictor — DR prevalence rises from under 5% after 5 years to over 80% after 20 years of Type 1 DM); poor glycaemic control (HbA1c above 8% doubles the risk of DR progression); hypertension (independent risk factor — UKPDS showed BP control reduces DR risk by 35%); dyslipidaemia (elevated LDL and triglycerides worsen DMO); nephropathy (microalbuminuria and CKD correlate with DR severity); pregnancy (rapid worsening of DR can occur in pre-existing diabetes during pregnancy); and smoking.

Critical point: diabetic retinopathy causes no symptoms in its early stages — by the time symptoms develop, significant damage has already occurred. This is why annual screening is essential. Early DR: completely asymptomatic. Moderate-severe NPDR: may remain asymptomatic or cause mild blurred vision (DMO). Diabetic macular oedema: gradual blurring and distortion of central vision, difficulty reading, faded colour perception, straight lines appearing wavy (metamorphopsia). Proliferative DR: sudden, dramatic visual loss from vitreous haemorrhage ('floaters', black spots, or total visual obscuration); or progressive visual field loss from tractional retinal detachment. Advanced PDR: secondary glaucoma (neovascular glaucoma — new vessels on the iris/angle occlude aqueous drainage), severe pain, and blindness. Fundoscopic signs: microaneurysms (earliest sign — small red dots); haemorrhages (dot and blot NPDR, flame-shaped in hypertension); hard exudates (lipid deposits at the macula in DMO); cotton-wool spots (nerve fibre layer infarcts in severe NPDR); venous beading; and neovascularisation (NVD — new vessels at the disc, or NVE — elsewhere on the retina).

Annual diabetic eye screening: digital fundus photography of both eyes (mydriatic or non-mydriatic) after dilating drops — national programmes detect pre-symptomatic DR across the diabetic population. In the UK, the NHS Diabetic Eye Screening Programme covers all people with diabetes over 12 years. Grading systems: Early Treatment Diabetic Retinopathy Study (ETDRS) scale: no DR, mild NPDR, moderate NPDR, severe NPDR (the 4-2-1 rule: 4 quadrants of haemorrhages, 2 quadrants of venous beading, 1 quadrant of IRMA), and PDR. Slit-lamp biomicroscopy: detailed retinal examination by an ophthalmologist — essential for DMO assessment. Optical coherence tomography (OCT): the gold standard for detecting and monitoring DMO — measures macular thickness, identifies centre-involving DMO (CI-DMO) requiring treatment, and monitors treatment response to anti-VEGF injections. Fluorescein angiography (FFA): intravenous dye imaging showing capillary non-perfusion (ischaemia), leakage from microaneurysms in DMO, and neovascularisation extent. OCT-angiography: non-invasive vasculature mapping. HbA1c, blood pressure, and lipids — systemic assessment at time of diagnosis.

Prevention through systemic control is the most effective treatment. Glycaemic control: achieving HbA1c below 48 mmol/mol (6.5%) reduces DR onset and progression (DCCT trial — intensive control reduced DR risk by 76% in Type 1 DM; UKPDS — 25% risk reduction in Type 2). Blood pressure control: target below 130/80 mmHg — ACE inhibitors and ARBs have additional renoprotective and possibly direct retinal protective effects. Lipid-lowering (fenofibrate): FIELD and ACCORD trials showed fenofibrate reduces DR progression (anti-VEGF-independent mechanism, possibly anti-inflammatory). Diabetic Macular Oedema (CI-DMO): anti-VEGF intravitreal injections are first-line — ranibizumab (Lucentis), aflibercept (Eylea), bevacizumab (Avastin — off-label), and faricimab (Vabysmo — bispecific anti-VEGF/anti-Ang2, reduces injection frequency to every 16 weeks in some patients); monthly injections initially with treat-and-extend or PRN protocols; dexamethasone implant (Ozurdex) for resistant DMO or pseudophakic eyes. Proliferative DR: pan-retinal photocoagulation (PRP) — laser to peripheral ischaemic retina destroys oxygen-demanding tissue, reducing VEGF drive to neovascularisation; still first-line for severe PDR. Anti-VEGF (ranibizumab/aflibercept) as alternative to PRP — DRCR Protocol S: non-inferior to PRP at 2 years, with better visual outcomes; avoids visual field loss. Vitrectomy: for non-clearing vitreous haemorrhage, tractional retinal detachment, and severe fibrovascular proliferation.

Vitreous haemorrhage from rupture of fragile proliferative neovascular vessels causes sudden dense visual loss — floaters progressing to total visual obscuration; often requires vitrectomy and may take months to clear spontaneously. Tractional retinal detachment from fibrovascular membranes in proliferative DR causes progressive or sudden visual field loss; macula-off tractional detachment requires urgent vitrectomy and carries a poor visual prognosis. Neovascular glaucoma (rubeosis iridis — iris neovascularisation occluding the drainage angle) causes severe pain, intraocular pressure frequently exceeding 50 mmHg, and rapid visual deterioration — extremely difficult to treat and frequently results in blindness despite aggressive management. Diabetic macular oedema (DMO) is the most common cause of vision loss in diabetes — untreated centre-involving DMO progresses to legal blindness (Snellen 6/60 or worse) in approximately 25% within 3 years. Persistent visual impairment from DR causes depression, anxiety, loss of driving ability, and occupational disability.

The DCCT and UKPDS trials definitively showed that tight glycaemic control (HbA1c below 7%) prevents or delays DR — this is the most important preventive measure. Attendance at annual diabetic eye screening is the single most important action a person with diabetes can take to protect their vision. All people with diabetes aged 12 and over should attend every year, even if they have no eye problems. Blood pressure management to below 130/80 mmHg using ACEi/ARBs as first-line agents in diabetes with proteinuria further reduces DR risk. Smoking cessation: reduces cardiovascular and microvascular complications across all diabetes types. Pre-pregnancy planning: women with pre-existing diabetes should have DR assessed before conception and receive enhanced screening throughout pregnancy — DR can worsen significantly in pregnancy, even with good control. Self-management education including recognition that DR is asymptomatic until advanced: patients must understand why screening attendance is essential even when vision feels normal.

Attend emergency ophthalmology immediately if you notice sudden visual loss, a large number of new floaters, a dark curtain or shadow appearing across vision, or any sudden change in vision — these symptoms can indicate vitreous haemorrhage or tractional retinal detachment, both requiring urgent assessment and possibly emergency vitrectomy. All people with diabetes should attend annual diabetic eye screening without fail — do not wait for symptoms, as significant DR causes no symptoms until late stages. Seek urgent ophthalmology review if you are pregnant with pre-existing diabetes (first trimester DR assessment is essential) or if a previous screening result showed moderate-severe NPDR or DMO requiring follow-up at shorter intervals. Any new visual symptoms in a person with diabetes — blurring, distortion, difficulty reading — should prompt review by an optometrist or GP for urgent ophthalmology referral.