Diabetic Retinopathy

Diabetic retinopathy is a medical condition characterised by damage to the retina due to long-term poor control of diabetes mellitus. It is a leading cause of blindness in developed countries, particularly among individuals aged 20 to 64. The longer a person has diabetes, the higher their risk of developing this condition.

Nearly all patients with type 1 diabetes and over 60% of those with type 2 diabetes experience some form of diabetic retinopathy over time.

Signs and Symptoms

In its early stages, diabetic retinopathy is often asymptomatic and can only be detected through a retinal exam. Over time, the condition progresses and can cause symptoms such as dark floating spots, flashes of light, and vision loss. Initial damage includes microaneurysms, cotton wool spots, haemorrhages, and lipid deposits in the retina. Advanced stages are marked by the growth of new blood vessels, which are prone to bleeding. Macular oedema, a common complication, can cause blurred vision and severe vision loss if it affects the macula's centre.

Diagnosis and Classification

Diabetic retinopathy is diagnosed through retinal exams using ophthalmoscopy. The American Academy of Ophthalmology classifies the condition into five categories based on severity: no apparent retinopathy, mild, moderate, and severe nonproliferative diabetic retinopathy (NPDR), and proliferative diabetic retinopathy. Macular oedema is separately categorised and assessed using optical coherence tomography and fluorescein angiography.

Screening

Due to its asymptomatic nature, regular eye exams are essential for early detection. The American Diabetes Association (ADA) and the International Council of Ophthalmology (ICO) recommend comprehensive eye exams for individuals with diabetes. These exams should include a visual acuity test and retinal examination via ophthalmoscopy or retinal photography.

Causes and Risk Factors

Diabetic retinopathy is caused by prolonged high blood glucose levels, which damage the small blood vessels of the retina. Major risk factors include the duration of diabetes, poor blood sugar control, and high blood pressure. Additional risk factors include kidney disease, abnormal blood lipids, high body mass index, and smoking. Genetic predispositions also play a role in developing this condition.

Pathogenesis

The pathogenesis of diabetic retinopathy involves damage to the small blood vessels and neurons of the retina. Initial changes include narrowing of the retinal arteries, neuronal dysfunction, and blood-retinal barrier breakdown. This leads to capillary degeneration, ischaemia, and microaneurysms. Advanced stages involve loss of capillary cells, increased vessel permeability, and the formation of new, fragile blood vessels, resulting in bleeding and scarring.

Management

Management includes anti-VEGF injections, steroid injections, panretinal laser photocoagulation, and vitrectomy. These treatments aim to slow or stop vision loss but do not cure diabetic retinopathy. Improving control of blood sugar, blood pressure, and blood cholesterol is essential to reduce disease progression.

Mild or Moderate NPDR

For mild to moderate NPDR, frequent retinal exams are recommended. Anti-VEGF drugs or steroids can reduce progression in approximately half of the cases, although long-term vision improvement remains uncertain.

Diabetic Macular Oedema

For patients with macular oedema, anti-VEGF injections are most beneficial, particularly those affecting the macula's centre. Laser photocoagulation is used for those unresponsive to injections.

Laser Photocoagulation

Laser photocoagulation treats macular oedema and controls neovascularisation in proliferative retinopathy. Panretinal photocoagulation is used for advanced stages, involving multiple laser burns to reduce oxygen demand and prevent ischaemia.

Surgery

Vitrectomy is indicated for severe cases with significant vitreous haemorrhage. It involves removing the vitreous gel and replacing it with a saline solution, often combined with other treatments.

Epidemiology

Approximately 35% of people with diabetes have some form of diabetic retinopathy, with 10% experiencing vision loss. It is more common in type 1 diabetes, affecting 80% of patients 15 years post-diagnosis. The global burden has increased significantly, particularly in low- and middle-income countries.

Research

Several large multicenter clinical trials have evaluated treatment protocols for diabetic retinopathy. Novel approaches such as light treatment, C-peptide therapy, and stem cell therapy are under investigation, although results have been mixed or inconclusive.

Fundoscopic Image Analyses

Fundoscopic images are very important for diagnosing diabetic retinopathy. Computer-aided diagnosis methods are being developed to automate the analysis of these images, improving detection accuracy and efficiency.

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Self-assessment MCQs (single best answer)

What is diabetic retinopathy primarily caused by?

Which age group is most commonly affected by diabetic retinopathy in developed countries?

Which diagnostic method is primarily used to detect diabetic retinopathy?

What percentage of patients with type 2 diabetes will experience some form of diabetic retinopathy over time?

Which treatment is most beneficial for patients with macular oedema affecting the centre of the macula?

What is the primary goal of panretinal laser photocoagulation in managing diabetic retinopathy?

Which stage of diabetic retinopathy is characterised by the growth of new blood vessels?

What does the American Academy of Ophthalmology classify as the initial stage of diabetic retinopathy?

Which risk factor is NOT directly associated with diabetic retinopathy?

What is the purpose of vitrectomy in the management of severe diabetic retinopathy?