Diabetic Retinopathy: Stages, Screening and Treatment Options

Diabetic retinopathy is damage to the small blood vessels of the retina caused by diabetes. The retina is the thin, light-sensitive layer at the back of the eye, and it depends on a dense network of tiny vessels for oxygen and nutrients. Over years, high blood sugar weakens and blocks these vessels. They may leak, close off or trigger the growth of fragile new vessels, all of which can threaten vision. Diabetic eye disease is one of the leading causes of vision loss in working-age adults worldwide, according to the World Health Organization and the International Diabetes Federation.

The crucial fact is that diabetic retinopathy usually causes no symptoms until it is advanced. Yet with regular screening, good control of blood sugar, blood pressure and cholesterol, and timely treatment, most severe vision loss from diabetes can be prevented. This guide explains how the disease progresses, what diabetic macular oedema is, how often you should be screened and what treatments are available.

How diabetes damages the retina

Persistently high blood glucose damages the inner lining of small vessels and the cells that support them. The vessel walls weaken and form tiny bulges called microaneurysms, which can leak blood and fluid. Some capillaries close completely, starving parts of the retina of oxygen. The oxygen-starved retina releases signals, especially a protein called vascular endothelial growth factor (VEGF), that stimulate new vessels to grow. These new vessels are fragile and grow in the wrong places, where they can bleed and form scar tissue. To understand where the retina fits in the eye, see our guide to eye anatomy.

Stages of diabetic retinopathy

Eye doctors grade retinopathy by severity. The exact names vary between countries and screening programmes, but the progression is similar everywhere.

Diabetic macular oedema can occur at any stage alongside the changes above.

Diabetic macular oedema

The macula is the central part of the retina that provides sharp reading and detail vision. When leaking vessels allow fluid to collect in or under it, the macula swells. This condition, called diabetic macular oedema (DMO, or DME in American spelling), is the most common reason people with diabetes lose vision. Symptoms include blurred or distorted central vision, colours appearing washed out and difficulty reading, though mild oedema may cause no symptoms at all. It is detected with optical coherence tomography (OCT), a quick, painless scan that shows the retinal layers in cross-section.

Symptoms

In the early stages there are none. When symptoms occur, they may include:

• Blurred or fluctuating vision.
• Dark spots, strings or cobweb-like floaters, which can indicate bleeding into the vitreous gel.
• Sudden loss of vision, partial or complete, in one eye.
• Difficulty seeing at night or poor colour perception.
• Distortion of straight lines.

Risk factors

• Duration of diabetes: the longer you have had diabetes, the higher the risk. After many years, most people with type 1 diabetes and a large proportion of those with type 2 show some retinopathy.
• Blood glucose control: higher HbA1c levels are strongly linked with onset and progression.
• High blood pressure: accelerates vessel damage. See high blood pressure and your eyes.
• High cholesterol and blood lipids: linked with hard exudates and macular oedema.
• Kidney disease, which often accompanies retinopathy.
• Pregnancy: retinopathy can progress faster during pregnancy in women with pre-existing diabetes.
• Smoking, which damages blood vessels throughout the body.

Screening: how often and what happens

Because early retinopathy is silent, regular screening is the most powerful tool to prevent sight loss. Many countries run national diabetic eye screening programmes. The usual approach is retinal photography: drops widen your pupils and a camera takes detailed pictures of the back of each eye. Some programmes add OCT scans. The appointment is painless, but your vision will be blurry and light-sensitive for a few hours, so you should not drive afterwards.

Some programmes extend the interval to two years for people at low risk with no retinopathy on two consecutive screens. Keep every appointment, even when your vision seems perfect. For general guidance on check-ups, see how often you should have an eye exam and our page on eye examinations.

Treatment options

Treatment aims to stop leakage, shrink abnormal vessels and prevent complications. It works best before vision is badly affected, which is why screening matters. Your ophthalmologist will choose treatment based on the type and stage of disease.

Anti-VEGF injections

Medicines that block VEGF are now the first-line treatment for macular oedema that affects central vision. They are injected into the eye after numbing drops, in a short clinic procedure. Treatment usually starts with injections every four weeks or so, then the interval is extended according to response. Major trials showed that many patients gain vision with this approach. Anti-VEGF can also be used to control proliferative retinopathy, although it needs reliable long-term follow-up because the effect wears off. In some cases, steroid implants are used for macular oedema, especially when anti-VEGF has not worked well.

Laser treatment

• Panretinal photocoagulation (PRP): hundreds to thousands of small laser burns are applied to the peripheral retina. This reduces the oxygen demand of the retina and the VEGF signal, causing abnormal vessels to regress. It has been a cornerstone treatment for proliferative retinopathy for decades and greatly reduces the risk of severe vision loss. Side effects can include reduced night vision and some loss of peripheral vision.
• Focal or grid laser: targeted laser for some forms of macular oedema, now used less often since injections became available, but still useful in selected cases.

Vitrectomy surgery

When there is a dense vitreous haemorrhage that does not clear, or scar tissue pulling on the retina (tractional retinal detachment), surgery may be needed. In a vitrectomy, the surgeon removes the vitreous gel along with blood and scar tissue, and may apply laser during the operation. Recovery takes weeks, and the outcome depends on how much the retina had been damaged beforehand. Learn more about retinal detachment.

Controlling glucose, blood pressure and lipids

Landmark studies, including the Diabetes Control and Complications Trial (DCCT) in type 1 diabetes and the UK Prospective Diabetes Study (UKPDS) in type 2 diabetes, showed that better blood glucose control and blood pressure control substantially reduce the risk of developing and worsening retinopathy. The benefit of earlier good control can last for many years.

• Blood glucose: work with your diabetes team on a personal HbA1c target. Very rapid improvement in very high levels can sometimes cause a temporary worsening of retinopathy, so people with significant retinopathy should have their eyes monitored when treatment is intensified.
• Blood pressure: keep it within the target your doctor sets.
• Lipids: treating high cholesterol is important for heart health; some evidence suggests certain lipid-lowering medicines may slow retinopathy.
• Lifestyle: stop smoking, stay active and follow a balanced diet. Our guide on nutrition for eye health offers practical tips.

Living with diabetic retinopathy

A diagnosis of retinopathy is a warning, not a verdict. Many people with mild disease never progress to sight-threatening stages, especially when risk factors are managed well. If you need treatment, regular attendance is essential; missed injection appointments are a common reason for losing vision gains. Eye exercises do not treat retinopathy and should never replace screening or medical treatment. If vision is reduced, low-vision services and aids can help you continue reading, working and living independently.

When to see a doctor

Attend your diabetic eye screening every time you are invited, and see an eye care professional if you notice gradual blurring, difficulty reading or new distortion. If you are pregnant and have diabetes, let your diabetes team know early so that extra eye checks can be arranged.