Diabetic Retinopathy

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:

GradingCharacteristicsManagement
Retinopathy
None (R0) Annual screening
Background (R1)Microaneurysms, retinal haemorrhages, venous loop, exudateAnnual screening
Pre-proliferative (R2)Venous beading, venous reduplication, IRMA, blot haemorrhagesRefer to Eye Services
Proliferative – active (R3a)Neovascularization, pre-retinal or vitreous haemorrhages, pre-retinal fibrosisRefer to Eye Services urgently
Proliferative – stable post-treatment (R3s)Peripheral retinal laser AND stable retina from fundus photogrpahyAnnual screening
Maculopathy
None (M0)NoneAnnual screening
Maculopathy (M1)Exudate / retinal thickening / microaneurysms / haemorrhage within 1 disc diameter of centre of foveaRefer 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 13

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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