Diabetes and eyes: diabetic retinopathy, from the first signs to treatment

You can have diabetic retinopathy and still read the newspaper, drive and recognise faces without difficulty. That is its most insidious side: in the early stages there are no symptoms, and the damage to the tiny blood vessels of the retina can advance silently until the most serious stages⁴.

Yet it is one of the most common complications of diabetes. A European systematic review, which pooled 35 studies of people with diabetes followed in primary care, estimated that 25.7% have some form of retinopathy¹. Worldwide, according to a meta-analysis of 59 population studies, about 103 million people had diabetic retinopathy in 2020, and the figure could reach 160 million by 2045².

In this article

1. What diabetic retinopathy is
2. How common it is, in Europe and worldwide
3. Diabetic retinopathy: the symptoms, when there are any
4. Why check-ups matter even when you see well
5. Blood sugar and blood pressure: what the studies have shown
6. Treatment when sight is at risk
7. Frequently asked questions
8. Sources

What diabetic retinopathy is

The retina, the thin layer of tissue at the back of the eye that turns light into signals for the brain, is nourished by a dense network of minuscule vessels. High blood sugar, over the years, damages them; and reviews point out that the nerve cells of the retina suffer too, not just the vessels³.

In the early, non-proliferative stage, the changes can be seen when the back of the eye is examined but usually cause no trouble. The forms that threaten sight are two: proliferative retinopathy, in which new, abnormal vessels grow, and macular oedema, in which fluid builds up in the macula, the small central area of the retina that is used for reading and recognising faces³.

The risk grows with the years of diabetes, with high blood sugar and with high blood pressure³. In the European review, retinopathy affected 54.4% of people with type 1 diabetes and 25.0% of those with type 2¹.

How common it is, in Europe and worldwide

The worldwide meta-analysis of 2021 estimated that about 22% of people with diabetes have retinopathy and 6% have a form that threatens sight: 28.5 million people in 2020, a figure that could approach 45 million in 2045².

In Europe, macular oedema was present in 3.7% of people with diabetes, and every year almost 5 in 100 people with type 2 diabetes developed a retinopathy they had not had before. The authors estimate that the number of people with an eye disease linked to diabetes will rise from 6.4 to 8.6 million by 2050, and that about 30% will need close monitoring or treatment¹.

Diabetic retinopathy: the symptoms, when there are any

Progression is often symptom-free until the advanced stages⁴. When problems do arrive, the most typical are blurred vision and images that look darker or distorted, sometimes differently in the two eyes; macular oedema, moreover, can appear at any stage of the disease⁵. Feeling well, then, is not enough: the stages at which there is most room to act can only be seen by looking at the retina.

Why check-ups matter even when you see well

The main tool is screening: photographs of the back of the eye, repeated over time, which make it possible to recognise the signs of the disease before they affect sight. Reviews name it, together with control of blood sugar and blood pressure, as one of the foundations for preventing blindness from diabetes³. Some programmes are also evaluating artificial intelligence to read photographs of the retina.

How often? The traditional answer is once a year, but not everyone needs the same rhythm.

Blood sugar and blood pressure: what the studies have shown

On blood sugar, the best-known evidence comes from a landmark study. The Diabetes Control and Complications Trial followed 1,441 people with type 1 diabetes for 6.5 years on average, randomly assigned to intensive treatment, aimed at keeping blood sugar close to normal values, or to the conventional treatment of the time. In people without retinopathy, intensive treatment reduced the risk of developing it by 76%; in those who already had a mild form, it slowed progression by 54%. These are reductions in relative risk, that is, in proportion to the starting risk. The price was a risk of severe hypoglycaemia two to three times higher⁶.

Blood pressure matters too. In the British study UKPDS 38, 1,148 people with type 2 diabetes and high blood pressure were followed for a median of 8.4 years: those assigned to tighter control had an average of 144/82 mmHg, against 154/87 in the other group. After nine years, with tighter control the risk of retinopathy worsening by two steps on the severity scale was 34% lower, and the risk of losing three lines on the eye chart was 47% lower, in relative terms⁷.

A 2023 Cochrane review, which pooled 29 randomised trials, offers a more nuanced picture. Lowering blood pressure more intensively reduced the appearance of retinopathy over five years by about 18%, in relative terms, with moderate-certainty evidence; it did not, however, clearly slow retinopathy that was already present, and the benefit mainly concerned people with type 2 diabetes and high blood pressure⁸. We also discuss the link between blood pressure and the retina in the article on hypertensive retinopathy.

Treatment when sight is at risk

Laser prevents severe loss of vision in eyes with proliferative retinopathy; injections into the eye of anti-VEGF drugs, which block a vessel growth factor, are indicated for macular oedema that is reducing vision³.

A 2023 Cochrane review compared anti-VEGF drugs with one another for macular oedema in 23 trials with 3,513 people. At two years no clear differences in vision emerged between the active substances compared; at one year some showed a small advantage, which may however be of no practical importance. Thirteen of the 23 trials were funded by industry¹⁰. How these injections work is explained in our article on macular degeneration. Which treatment to choose, and when, is decided with the ophthalmologist.

Frequently asked questions

Does diabetic retinopathy cause symptoms at the start?

Usually not: it often progresses without symptoms until the advanced stages⁴. When they do appear, the most typical are blurred vision and dark or distorted images⁵.

How often should you have your retina checked with diabetes?

It depends on each person’s risk and on how screening is organised where you live. In a large English trial, intervals of 6, 12 or 24 months set according to risk worked as well as annual screening, with fewer appointments⁹. The interval is decided by whoever follows you.

If blood sugar is under control, is the retina safe?

The risk is greatly reduced, but it does not disappear: in the DCCT trial, intensive treatment reduced it by 76%⁶. The years of diabetes and blood pressure also count^3,7, so check-ups remain necessary.

Can diabetic retinopathy be cured?

For the stages that threaten sight there is laser, in the proliferative form, and anti-VEGF injections, in macular oedema with reduced vision^3,10. Their aim is above all to preserve sight: that is why recognising the disease early matters.

Diabetic retinopathy is a disease that can be seen before it is felt, provided someone looks at the retina. The studies of the past thirty years say that keeping blood sugar and blood pressure under control reduces the risk^6,7, that check-ups can be calibrated to each person’s risk⁹ and that, when needed, treatments exist^3,10.