Diabetic Retinopathy: How Diabetes Affects Your Eyes (and How to Protect Them)

Diabetic retinopathy is the leading cause of blindness in adults — largely preventable. Learn the stages, symptoms, and how to protect your vision.

Diabetic retinopathy is damage to the blood vessels of the retina caused by persistently high blood sugar. It is the leading cause of blindness in working-age adults worldwide. Early stages have no symptoms — vision loss only occurs once the disease is advanced. The most effective protections are blood sugar control, blood pressure management, not smoking, and annual dilated eye examinations. Early detection allows treatment that prevents vision loss in most cases.

At a Glance

• Affects approximately 1 in 3 people with diabetes who have had the condition for more than 20 years.
• Early stages (background retinopathy) cause no symptoms — vision seems normal.
• Advanced stages cause blurred vision, floaters, or sudden vision loss.
• The leading cause of new blindness in adults of working age in developed countries.
• Annual dilated eye examination detects it before vision loss occurs.
• Blood sugar control is the single most effective prevention.

What Is the Retina and Why Does Diabetes Affect It?

The retina is the light-sensitive tissue lining the back of the eye — it converts light into signals sent to the brain via the optic nerve. It has an extremely dense network of tiny blood vessels. High blood sugar damages these vessels over time: they leak fluid, swell, grow abnormally, or close off — disrupting the retina's blood supply and impairing vision.

Stages of Diabetic Retinopathy

• Non-proliferative diabetic retinopathy (NPDR) — early stage: tiny bulges (microaneurysms) appear in vessel walls; some vessels leak fluid or bleed; hard exudates (fatty deposits) may appear.
• Moderate to severe NPDR: more vessels are blocked and the retina signals the need for new blood vessel growth.
• Proliferative diabetic retinopathy (PDR) — advanced stage: new fragile blood vessels grow on the retina and into the vitreous (the gel inside the eye); these vessels bleed easily, causing floaters or vision loss; scar tissue can form and pull the retina, causing detachment.
• Diabetic macular oedema (DMO): fluid leaks into the macula (the central retina responsible for sharp vision) at any stage; DMO is the most common cause of vision loss in diabetic retinopathy.

Symptoms of Diabetic Retinopathy

Early-stage diabetic retinopathy produces no symptoms at all — damage is already occurring long before you notice anything. This is precisely why regular screening is essential for every person with diabetes, not just those experiencing vision changes.

• Blurred or fluctuating vision.
• Floaters (spots, strings, or cobwebs drifting across vision).
• Dark or empty areas in vision.
• Difficulty with colour perception.
• Sudden vision loss (from vitreous haemorrhage or retinal detachment).
• Early stages produce no symptoms at all — damage is already occurring before you notice anything.

Risk Factors for Diabetic Retinopathy

• Duration of diabetes — the longer you have had diabetes, the greater the risk.
• High blood sugar (high A1C) — the most modifiable risk factor.
• High blood pressure — hypertension damages retinal vessels independently.
• High cholesterol — contributes to exudate formation in the retina.
• Smoking — reduces blood flow and accelerates vascular damage.
• Pregnancy — can worsen retinopathy.
• Kidney disease — shares vascular risk factors and often occurs alongside retinopathy.

Eye Screening: Why Annual Examinations Are Essential

Because early retinopathy causes no symptoms, the only way to detect it before vision loss occurs is through regular dilated eye examination. A camera photographs the retina and an optometrist or ophthalmologist examines the images for early changes.

• People with diabetes should have a dilated retinal photograph at diagnosis and annually thereafter.
• Digital retinal cameras can detect changes too subtle to notice clinically — this is why an ordinary vision test is NOT sufficient.
• If changes are found, the frequency of examinations increases.
• In the UK, NHS Diabetic Eye Screening is offered annually to all people with diabetes aged 12+.

How to Prevent and Slow Diabetic Retinopathy

No single measure eliminates retinopathy risk entirely, but the combination of rigorous blood sugar management, blood pressure control, and lifestyle changes dramatically reduces both the likelihood of developing retinopathy and the speed of its progression.

• Blood sugar control: keeping A1C under 7% reduces the risk of retinopathy developing and slows its progression — the DCCT trial showed intensive control reduced retinopathy risk by 76% in type 1 diabetes.
• Blood pressure control: target under 130/80 mmHg — the UKPDS showed tight blood pressure control reduced retinopathy progression by 34%.
• Stop smoking: smoking constricts retinal blood vessels and accelerates damage.
• Cholesterol management: statins and a heart-healthy diet reduce exudate formation.
• Regular eye screening: early detection means earlier treatment.
• Maintain a healthy weight and exercise regularly: both reduce blood pressure and improve blood sugar control.

Treatment for Diabetic Retinopathy

• Laser photocoagulation: laser seals leaking blood vessels and destroys areas of abnormal vessel growth — the gold-standard treatment for proliferative retinopathy for decades.
• Anti-VEGF injections (e.g. ranibizumab, bevacizumab, aflibercept): injected into the eye to block the signal that drives abnormal vessel growth.
• The preferred treatment for diabetic macular oedema — highly effective at preserving central vision.
• Vitrectomy: surgical removal of vitreous gel when there is significant haemorrhage or traction retinal detachment.
• Early treatment can prevent vision loss in up to 90% of cases when detected before advanced disease.

Frequently Asked Questions

Can diabetic retinopathy be reversed?

Early non-proliferative retinopathy may partially stabilise or even improve with sustained blood sugar control. However, once advanced retinopathy (proliferative stage) or significant macular oedema has developed, the changes cannot be fully reversed — the goal shifts to halting progression and preserving remaining vision. This is why early detection through regular screening is so important; damage caught early gives the best chance of treatment before irreversible loss occurs.

Does retinopathy always lead to blindness?

No. Most people with diabetic retinopathy do not go blind. Blindness typically results from advanced untreated retinopathy or from late-presenting macular oedema. With regular eye screening, early treatment significantly reduces this risk. Studies show that timely laser or anti-VEGF treatment prevents severe vision loss in the vast majority of patients when retinopathy is caught before the advanced stage.

Can I notice retinopathy without an eye test?

Not in the early stages. Mild to moderate non-proliferative retinopathy causes no change in vision — you cannot feel or see that damage is occurring. This is why annual retinal photography is essential; it detects changes years before they affect your sight. Symptoms (floaters, blurred vision, dark patches) only appear in more advanced stages when treatment is harder and outcomes are less predictable.

Sources

• American Diabetes Association (ADA) — diabetes.org
• NHS — nhs.uk
• National Eye Institute (NEI) — nei.nih.gov
• Mayo Clinic — mayoclinic.org

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