Diabetic Retinopathy: Causes, Screening and Treatment

Diabetic Retinopathy: Causes, Screening and Treatment

Diabetic retinopathy (DR) is a diabetes-related eye disease in which damaged retinal blood vessels can cause vision loss. Screening matters because early disease may have no noticeable symptoms.

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): A specialist grades the extent and severity of retinal haemorrhages, venous beading and intraretinal microvascular abnormalities (IRMA). The 4-2-1 classification includes lesion-severity criteria; simply counting affected quadrants is insufficient. Severe disease requires prompt specialist assessment and monitoring.

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) involves the central macula. Management depends on visual acuity and retinal findings: some people with good vision can be monitored, while visual impairment may warrant 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 longer someone has diabetes, the greater their risk of diabetic retinopathy. Individual risk also depends on systemic control and other factors.

Glycaemic control (HbA1c) — in the DCCT, people with type 1 diabetes were followed for an average of 6.5 years. Compared with the conventional-treatment group, intensive treatment reduced the relative risk of developing retinopathy by 76% in participants without retinopathy at baseline, and progression by 54% in those with early retinopathy. Average HbA1c was about 7% versus 9%. These are trial-group results, not a fixed benefit for each percentage-point reduction in an individual patient. Intensive treatment also increased hypoglycaemia risk; targets should be agreed with the diabetes team.

Blood pressure control — hypertension contributes to risk. Agree an individual blood-pressure goal with the diabetes care team.

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 with pre-existing diabetes: arrange retinal assessment after the first antenatal appointment unless a recent assessment makes it unnecessary under the clinical pathway. Repeat assessment is needed during pregnancy even if the first assessment shows no retinopathy; additional monitoring depends on the findings. NICE recommends another assessment at 28 weeks and an additional assessment at 16–20 weeks when 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

Systemic care remains important alongside eye treatment:

• Agree individual blood-glucose and blood-pressure goals with the diabetes team.
• Review kidney disease, cholesterol and cardiovascular risk.
• Seek smoking-cessation support if needed.
• Discuss whether any additional medicine is appropriate; do not start or change diabetes or lipid treatment based on this article.

Anti-VEGF Injections for Diabetic Macular Oedema

Intravitreal anti-VEGF injections are an important option for centre-involving DMO with visual impairment. Observation or other treatments may be appropriate depending on vision, retinal findings and follow-up reliability:

Drug	Frequency	Evidence
Ranibizumab (Lucentis)	Specialist-directed regimen	One of the anti-VEGF medicines studied in DRCR.net Protocol T
Aflibercept (Eylea)	Specialist-directed regimen	One of the anti-VEGF medicines studied in DRCR.net Protocol T
Bevacizumab (Avastin)	Specialist-directed regimen	Studied in DRCR.net Protocol T; ocular use and local regulatory status must be checked
Faricimab (Vabysmo)	Individualised intervals after loading, determined by the retinal specialist and applicable product information	YOSEMITE and RHINE studied diabetic macular oedema: visual-acuity outcomes were non-inferior to aflibercept under the trial regimens, including an individualised extended-interval arm

Anti-VEGF treatment can improve vision and reduce retinal swelling. Repeat treatment and monitoring may be needed; recurrence is possible, so changes or pauses should be agreed with the retinal specialist.

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. In the historical Diabetic Retinopathy Study (DRS), laser-treated study eyes had about a 50% relative reduction in severe vision loss compared with control eyes. The trial endpoint was visual acuity below 5/200 at two visits four months apart. This result applies to the trial population and treatment context; it is not an individual guarantee or a 50-percentage-point absolute reduction.

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: NICE recommends considering vitrectomy when haemorrhage in proliferative diabetic retinopathy has not cleared within 3 months. This is not a rule to delay assessment or indicated surgery: macula-involving or macula-threatening retinal detachment requires surgical consideration independently of that interval. The retinal specialist determines timing from the findings and individual circumstances.
• 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:

Before arranging retinal care in China, ask the receiving team to confirm:

• Which retinal imaging and screening tests are needed.
• The exact injection medicine, local authorisation, treatment plan and monitoring schedule.
• Whether laser or vitreoretinal surgery is indicated and how follow-up will work.
• How eye care will be coordinated with diabetes and kidney care.
• An itemised hospital quote and the separately agreed scope of PriumCare coordination.

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

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Source for this targeted correction

• FDA clinical review of faricimab, BLA 761235. This US regulatory review supports the trial description; it does not establish Chinese approval, availability or an individual treatment schedule.

• NEI diabetic retinopathy information.

• NICE NG242 recommendations.

• DRCR.net Protocol T primary trial.

• NIDDK summary of DCCT/EDIC.

• NEI teaching review of the Diabetic Retinopathy Study, slide 25.

Editorial source correction: 25 October 2026. This targeted check addressed the flagged treatment, surveillance, product and availability claims, and removed unsupported numerical or comparative promises. It is not a clinical review of the whole article. No named medical reviewer is claimed. Original publication date is retained.

Targeted pregnancy monitoring and surgical-timing clarification

Editorial source check: 26 October 2026. This update clarifies only retinal assessment during pregnancy with pre-existing diabetes and the limits of the non-clearing haemorrhage timing statement. It is not a whole-article medical review and adds no named clinical reviewer. The original publication date is retained.

• NICE NG3: retinal assessment during pregnancy, recommendation 1.3.25
• NICE NG242: vitrectomy recommendations 1.5.7–1.5.9