Diabetic Retinopathy

Diabetic retinopathy is a chronic, progressive microvascular complication of diabetes mellitus that damages the small blood vessels of the retina. It is one of the leading causes of preventable blindness in working-age adults, and its severity broadly parallels the duration and control of diabetes. The disease is classified along a continuum from non-proliferative changes to sight-threatening proliferative retinopathy and diabetic macular oedema.

Definition

Diabetic retinopathy is a microvascular complication of diabetes characterised by progressive damage to the retinal vasculature, ranging from microaneurysms and haemorrhages in the non-proliferative stage to retinal neovascularisation in the proliferative stage, and frequently accompanied by diabetic macular oedema.

Scope

This entry covers the pathophysiology, classification, epidemiology, and clinical significance of diabetic retinopathy as a topic within retinal and vitreous disease. It addresses the microvascular mechanisms, the non-proliferative and proliferative stages, and diabetic macular oedema as the principal cause of central vision loss in the condition. It is a reference entry and does not provide treatment protocols.

Core questions

• How does chronic hyperglycaemia damage the retinal microvasculature?
• What distinguishes non-proliferative from proliferative diabetic retinopathy?
• Why does diabetic macular oedema cause central vision loss independent of retinopathy stage?
• Which systemic factors most strongly influence the onset and progression of retinopathy?

Key concepts

• Microaneurysms and retinal haemorrhages
• Non-proliferative diabetic retinopathy
• Proliferative diabetic retinopathy
• Retinal neovascularisation
• Diabetic macular oedema
• Blood-retinal barrier breakdown
• Retinal ischaemia and capillary non-perfusion
• Vascular endothelial growth factor

Mechanisms

Chronic hyperglycaemia injures the retinal microvasculature through interacting pathways, including increased polyol and hexosamine flux, accumulation of advanced glycation end products, activation of protein kinase C, and oxidative and inflammatory stress. These changes cause loss of pericytes and endothelial cells, thickening of the basement membrane, and breakdown of the blood-retinal barrier, producing microaneurysms, haemorrhages, and increased vascular permeability with leakage into the macula (diabetic macular oedema). Progressive capillary closure leads to retinal ischaemia, which upregulates vascular endothelial growth factor and other angiogenic mediators; this drives pathological neovascularisation on the retina and optic disc that characterises the proliferative stage and can cause vitreous haemorrhage and tractional detachment (antonetti-2012; cheung-2010).

Clinical relevance

Diabetic retinopathy is a major cause of vision impairment in adults with diabetes, and understanding its staging underpins the rationale for systematic retinal screening in diabetes care. Because much retinopathy is asymptomatic until advanced, the condition illustrates why surveillance and risk-factor awareness matter at a population level. This entry is descriptive and educational and does not constitute screening intervals or treatment advice for any individual.

Epidemiology

A pooled analysis of population-based studies estimated that about one in three people with diabetes have some diabetic retinopathy and roughly one in ten have vision-threatening retinopathy, with longer diabetes duration, higher glycated haemoglobin, and higher blood pressure as the strongest associated risk factors. As global diabetes prevalence rises, the absolute burden of diabetic retinopathy is increasing (yau-2012; cheung-2010).

Evidence & guidelines

The modern understanding of diabetic retinopathy rests on landmark interventional and observational research summarised in major reviews, including the role of glycaemic and blood-pressure control in slowing progression and the central place of vascular endothelial growth factor in the proliferative and oedematous disease. Specific clinical guidance is set by professional bodies; this entry summarises the evidence framework rather than reproducing protocols (antonetti-2012; cheung-2010; yau-2012).

History

Diabetic retinopathy was recognised clinically in the nineteenth century after the ophthalmoscope made the fundus visible, but its management was transformed in the later twentieth century by panretinal photocoagulation, which reduced severe visual loss in proliferative disease, and by the development of vitrectomy for its complications. In the twenty-first century, the identification of vascular endothelial growth factor as a driver of neovascularisation and macular oedema underpinned anti-angiogenic pharmacotherapy, reshaping treatment of the condition (antonetti-2012; cheung-2010).

Seminal works

• antonetti-2012
• cheung-2010
• yau-2012

Frequently asked questions

What is the difference between non-proliferative and proliferative diabetic retinopathy?

Non-proliferative diabetic retinopathy involves microvascular changes within the retina such as microaneurysms and haemorrhages, whereas proliferative diabetic retinopathy is defined by the growth of new, abnormal blood vessels in response to retinal ischaemia, which can bleed and lead to tractional retinal detachment.

Can someone have good vision and still have diabetic retinopathy?

Yes. Early and even moderately advanced retinopathy is often asymptomatic, which is why retinal examination is used to detect disease before vision is affected; sight loss frequently relates to macular oedema or proliferative complications.