Overview
Diabetes mellitus can cause both macrovascular (e.g., myocardial infarction, peripheral vascular disease, stroke) and microvascular (e.g., nephropathy, neuropathy, retinopathy) complications. Diabetic retinopathy is the most common microvascular complication of diabetes and is one of the most common causes of blindness in working-aged adults globally. The risk of retinopathy varies depending on several factors including type of disease (type 1 vs type 2), duration of disease, glycaemic control, smoking, hypertension and pregnancy1,2.
Screening
The NHS Diabetic Eye Screening Programme invites all people over the age of 12 for annual digital photographic screening of the retina. There are several different grading systems for diabetic retinopathy, however the traditional ‘background, pre-proliferative and proliferative’ is a useful grading tool for daily clinical practice and has been adopted by the UK National Screening Committee:
Grading | Characteristics | Management |
Retinopathy | ||
None (R0) | Annual screening | |
Background (R1) | Microaneurysms, retinal haemorrhages, venous loop, exudate | Annual screening |
Pre-proliferative (R2) | Venous beading, venous reduplication, IRMA, blot haemorrhages | Refer to Eye Services |
Proliferative – active (R3a) | Neovascularization, pre-retinal or vitreous haemorrhages, pre-retinal fibrosis | Refer to Eye Services urgently |
Proliferative – stable post-treatment (R3s) | Peripheral retinal laser AND stable retina from fundus photogrpahy | Annual screening |
Maculopathy | ||
None (M0) | None | Annual screening |
Maculopathy (M1) | Exudate / retinal thickening / microaneurysms / haemorrhage within 1 disc diameter of centre of fovea | Refer to Eye Services |
Ungradeable | Refer to Eye Services |
Timing of referral to an ophthalmologist is guided by the risk of visual loss. Here are some guidelines as to how urgently to refer:
Immediate referral:
- Rubeosis iridis / neovascular glaucoma
- Vitreous haemorrhage
- Retinal detachment
Urgent referral (<2 weeks):
- Proliferative retinopathy
Routine referral (<13 weeks):
- Pre-proliferative retinopathy
- Maculopathy
- Cataracts
Annual screening:
- Background retinopathy – inform the diabetes care team
- No retinopathy – after 2 consecutive negative annual screens, can be screened two-yearly
Signs
Hyperglycaemia leads to pericyte damage causing endothelial cell injury and subsequent capillary occlusion and ischaemia. Ischaemia leads to overproduction of vascular endothelial growth factor (VEGF) and new vessel formation which can easily bleed. This process leads to some common signs of diabetic retinopathy seen on the retina:
- Microaneurysms
- Small red dots, outpouchings of the capillary wall
- Hemorrhage
- Retinal venule haemorrhage: appears as “dot” and “blot” haemorrhages; retinal arteriole haemorrhage: appears as “flame shaped”
- Exudate
- Yellow waxy lesions, these are leakage of proteins from the capillaries
- Cotton wool spots
- Fluffy white patches of infarcted retina
- Intraretinal microvascular abnormalities (IRMAs)
- Fine intraretinal arteriovenous shunts


Image 1: Rakhlin, Alexander. (2018). Diabetic Retinopathy detection through integration of Deep Learning classification framework. 10.1101/225508.
In advanced diabetic eye disease, damage may lead to tractional retinal detachment, persistent vitreous haemorrhage and neovascular glaucoma.
Diagnosis
Whist diabetic retinopathy is often asymptomatic, patients may report a reduction in visual acuity, distortion and vitreous floaters. When taking a history, include past ocular and medical history and ensure to ask questions on diabetes control including current medication and recent HbA1c and blood pressure control.
When examining, look carefully for the presence of abnormal blood vessels on the iris (rubeosis), cataract, vitreous cells and perform a detailed dilated fundus examination checking for microaneurysms, haemorrhage, hard exudates, cotton wool spots and signs of macular oedema.
Optical Coherence Tomography (OCT) is a useful tool to assess for the presence of intraretinal or subretinal fluid. Fluorescein angiography (FA) and optical coherence tomography-angiography (OCT-A) may also be used to detect vascular abnormalities and ischaemia
Management
Management of diabetic retinopathy is guided by the severity. In the early stages (i.e., background to pre-proliferative), screening, observation, lifestyle changes (e.g. smoking cessation) and management of existing disease such as tight glycaemic, blood pressure and cholesterol control are important.
For later stages (i.e., proliferative to diabetic macular oedema) management may involve laser photocoagulation, anti-VEGF injections (e.g. Ranibizumab and Aflibercept) and intravitreal steroid implants (e.g. Ozurdex) to prevent further vision loss.
References
1 UK Prospective Diabetes Study ( UKPDS) Group. Relationship between the severity of retinopathy and progression to photocoagulation in patients with Type 2 diabetes mellitus in the UKPDS (UKPDS 52). Diabet Med 2001; 18: 178–184
2 Nathan DM, Genuth S, Lachin J, et al..; Diabetes Control and Complications Trial Research Group . The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus. N Engl J Med 1993;329:977–986
Written by Dr Sandra Halim IMT2 (MBBS BSc PhD – PhD: Characteristics of Non-Responders in Diabetic Retinopathy) & reviewed by Dr David McMaster ST1 Ophthalmology
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