Diabetic Retinopathy: Causes, Screening and Treatment

Diabetic retinopathy (DR) is the most common microvascular complication of diabetes mellitus and the leading cause of new-onset blindness in working-age adults (20–74 years) in developed countries. It affects approximately one-third of people with diabetes — roughly 100–130 million people globally — and is responsible for approximately 4.8% of the 37 million cases of blindness worldwide.

Despite this burden, the vision loss caused by diabetic retinopathy is largely preventable: rigorous control of blood glucose and blood pressure dramatically reduces incidence and progression; regular retinal screening detects changes before vision is threatened; and modern treatments — laser, anti-VEGF injections, and vitreoretinal surgery — can prevent most diabetes-related blindness when applied at the right time.

How Diabetes Damages the Retina

The retina is one of the most metabolically active tissues in the body, with high oxygen and glucose demands. Chronic hyperglycaemia (elevated blood glucose) causes multiple pathological changes in the retinal microvasculature:

Pericyte loss — pericytes are contractile support cells wrapped around retinal capillaries that regulate blood flow and maintain the blood-retinal barrier. They are selectively vulnerable to hyperglycaemia; their loss weakens capillary walls.

Basement membrane thickening — glucose-driven biochemical changes thicken and alter the structural properties of capillary basement membranes.

Endothelial cell dysfunction and loss — the inner lining of capillaries becomes dysfunctional; the blood-retinal barrier breaks down, allowing protein and fluid leakage.

Microaneurysm formation — focal weakening of capillary walls produces small outpouchings (microaneurysms), the earliest clinically detectable sign of diabetic retinopathy.

Capillary occlusion and ischaemia — progressive capillary closure produces areas of non-perfused, ischaemic retina.

VEGF upregulation — ischaemic retina produces excess vascular endothelial growth factor (VEGF), which drives pathological new vessel formation (neovascularisation) and macular oedema.

Classification and Stages

Non-Proliferative Diabetic Retinopathy (NPDR)

In NPDR, abnormalities are confined within the retina — no new vessels have grown outside the retina or onto the optic disc. NPDR is graded by the number and severity of lesions:

Mild NPDR: A few microaneurysms only. Approximately 15% progress to proliferative DR within 5 years.

Moderate NPDR: Microaneurysms, dot and blot haemorrhages, hard exudates (lipid deposits leaking from damaged vessels), and cotton wool spots (focal areas of nerve fibre layer ischaemia appearing as white fluffy patches). Progression risk approximately 30–50% at 5 years.

Severe NPDR (Pre-proliferative): Defined by the "4-2-1 rule" — any of: haemorrhages in all 4 quadrants; venous beading in 2 or more quadrants; intraretinal microvascular abnormalities (IRMA) in 1 or more quadrants. High risk of progression to PDR: 50% within 1 year. Urgent referral required.

Proliferative Diabetic Retinopathy (PDR)

Extensive retinal ischaemia drives VEGF-induced neovascularisation — fragile new blood vessels grow on the surface of the retina or optic disc (NVD — neovascularisation of the disc; NVE — elsewhere) and into the vitreous gel.

These new vessels are fragile and prone to rupture, causing:

• Vitreous haemorrhage — sudden, severe visual blurring or complete vision loss from blood flooding the vitreous; spontaneous partial absorption over weeks to months but recurrent bleeding is common
• Tractional retinal detachment — fibrovascular proliferative membranes develop on the neovascular scaffold; as the vitreous contracts, these membranes exert traction on the retina, pulling it off the underlying RPE — a sight-threatening emergency
• Rubeosis iridis (iris neovascularisation) — new vessels on the iris, preceding neovascular glaucoma

Diabetic Macular Oedema (DMO)

Diabetic macular oedema — swelling of the macula due to leakage of fluid and protein through damaged capillary walls — can occur at any stage of diabetic retinopathy, including early NPDR, and is the most common cause of vision loss in diabetic patients.

Centre-involving DMO (CI-DMO) — fluid involves the central subfield of the macula (the fovea); associated with significant visual acuity loss. Requires treatment.

Non-centre-involving DMO — fluid outside the foveal centre; often manageable with closer monitoring initially.

DMO is diagnosed by OCT, which precisely quantifies central retinal thickness and identifies the pattern of fluid (intraretinal vs subretinal).

Risk Factors and Prevention

Duration of diabetes — the most powerful predictor. After 20 years of type 1 diabetes, nearly 100% of patients have some degree of retinopathy; after 15 years of type 2 diabetes, approximately 80%.

Glycaemic control (HbA1c) — the DCCT and UKPDS landmark trials demonstrated that tight glycaemic control dramatically reduces the risk of diabetic retinopathy:

• The DCCT showed that intensive insulin therapy reducing HbA1c from 9% to 7% reduced the development of retinopathy by 76% and progression by 54%
• Each 1% reduction in HbA1c reduces retinopathy risk by approximately 40%

Blood pressure control — hypertension independently accelerates diabetic retinopathy; target BP <130/80 mmHg

Other risk factors: duration of diabetes, lipid levels (dyslipidaemia associated with hard exudate formation and DMO), nephropathy (renal disease and retinopathy progress together), pregnancy (can accelerate retinopathy rapidly — urgent ophthalmological review required).

Screening

Annual dilated fundus examination (or digital retinal photography) is the cornerstone of diabetic retinopathy prevention:

• Type 1 diabetes: start screening 5 years after diagnosis; then annually
• Type 2 diabetes: start at diagnosis (retinopathy may already be present); then annually
• Pregnancy: at booking visit; more frequently if retinopathy is present

Diabetic retinal screening programmes using digital fundus photography have demonstrated dramatic reductions in diabetes-related blindness in countries with organised screening (Finland, UK, Iceland).

Treatment

Systemic Risk Factor Optimisation

The most powerful interventions are systemic — not ophthalmic:

• HbA1c target ≤7% (53 mmol/mol); individual targets based on age and comorbidities
• Blood pressure control (<130/80 mmHg); ACE inhibitors or ARBs preferred in diabetic nephropathy
• Lipid management (statin therapy for cardiovascular risk reduction)
• Smoking cessation
• Fenofibrate (lipid-modifying agent) shown in FIELD and ACCORD-Eye trials to reduce need for laser in type 2 diabetes

Anti-VEGF Injections for Diabetic Macular Oedema

Intravitreal anti-VEGF injections have replaced focal/grid laser as the first-line treatment for centre-involving DMO:

Drug	Frequency	Evidence
Ranibizumab (Lucentis)	Monthly to bimonthly	RIDE/RISE trials: gains 10–12 letters vs 2–3 with sham
Aflibercept (Eylea)	Loading then 8-weekly	VIVID/VISTA: superior to macular laser; bimonthly after loading
Bevacizumab (Avastin)	Monthly	Off-label; cost-effective; used in DRCR.net Protocol T
Faricimab (Vabysmo)	Up to 16-weekly	Protocol AF: non-inferior to aflibercept; extended dosing

Anti-VEGF injections improve visual acuity, reduce retinal thickness, and reduce VEGF-driven neovascularisation. Treatment is ongoing — discontinuation leads to recurrence.

Intravitreal corticosteroids (dexamethasone implant — Ozurdex; fluocinolone acetonide — Iluvien): alternatives when anti-VEGF is insufficient or in pseudophakic (post-cataract) patients; longer-lasting effect but raise IOP and accelerate cataract.

Laser Photocoagulation

Panretinal photocoagulation (PRP) — for proliferative DR: Wide-field laser burns applied to ischaemic peripheral retina destroy VEGF-producing cells, reducing neovascular drive and causing regression of new vessels. PRP remains important for PDR, particularly when anti-VEGF is not feasible. Reduces severe vision loss risk by 50%.

Focal/grid laser — for DMO: Less used since anti-VEGF became standard; still plays a role in non-centre-involving DMO and as adjunct to anti-VEGF.

Vitreoretinal Surgery

Vitrectomy — surgical removal of the vitreous gel — is indicated for:

• Non-clearing vitreous haemorrhage (persistent dense blood blocking vision >3 months)
• Tractional retinal detachment involving or threatening the macula
• Dense premacular haemorrhage (blood beneath the internal limiting membrane)

Modern vitrectomy uses 23–25 gauge (micro-incision) instrumentation; the vitreous is removed, tractional membranes are peeled from the retinal surface, and endolaser is applied. The eye is usually filled with gas or silicone oil tamponade. Vision recovery depends on the duration and extent of macular involvement.

Diabetic Retinopathy Care in China

China's diabetic eye disease and vitreoretinal centres offer:

• Diabetic eye screening: digital fundus photography, slit-lamp biomicroscopy, and OCT; integrated with systemic diabetes review
• Anti-VEGF injection clinic: ranibizumab, aflibercept, and faricimab available; high-volume injection clinics with experienced retinal specialists
• Panretinal laser: PRP performed with modern laser platforms; same-session bilateral treatment available
• Vitreoretinal surgery: high-volume vitrectomy teams experienced in complex tractional retinal detachment repair and severe PDR; 25G micro-incision vitrectomy as standard
• Coordinated diabetic care: ophthalmic assessment integrated with endocrinology for HbA1c optimisation and nephropathy screening
• Cost: care in China is generally less expensive than UK private treatment, but the hospital prices each case individually — ask us for the written quote before you commit.
• Full English care navigation from assessment through injection therapy, laser, and surgery

Contact a ChinaMedicalTour care navigator to arrange a diabetic eye screening, macular assessment, or retinal surgery consultation.

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Medical content based on MSD Manuals and international diabetic retinopathy guidelines. Evidence reviewed 2025.

Frequently Asked Questions

Can international patients schedule comprehensive eye examinations and specialist consultations in China?

Yes. Comprehensive ophthalmic evaluations including optical coherence tomography (OCT), visual field testing, corneal topography, and fundus photography are coordinated at specialized eye hospitals.

What specialized ophthalmic treatments and laser therapies are evaluated in China?

Tertiary ophthalmology centers offer micro-incision cataract surgery, anti-VEGF intravitreal injections, retinal photocoagulation, and minimally invasive glaucoma procedures tailored to individual eye pathology.

How is post-treatment follow-up handled for traveling eye patients?

Follow-up visual checks, eye drop regimens, and detailed bilingual ophthalmic clinical notes are provided upon discharge to ensure seamless continuation with domestic eye care providers.