Diabetic retinopathy

What causes diabetic retinopathy?

Diabetes affects how the body regulates blood sugar (glucose) levels. When these are too high, blood vessels throughout the body can become damaged, which can result in serious complications.

Diabetic retinopathy results from damage caused by diabetes to the blood vessels that supply oxygen to the retina – which is responsible for converting light passing through the eye into the signals sent to the brain that enable us to see.

However, exactly how and why these changes happen is not yet fully understood. The three main stages of diabetic retinopathy are:

Stage 1: Background diabetic retinopathy Background diabetic retinopathy is the earliest detectable stage, when small swellings develop in the capillaries (tiny blood vessels). These don’t normally affect vision but monitoring them closely is important.

Stage 2: Pre-proliferative diabetic retinopathy At this stage more widespread changes are seen in the retina, including severe bleeding into the retina. There is a high risk that your vision could eventually be affected.

Stage 3: Proliferative diabetic retinopathy This is an advanced stage of diabetic retinopathy, which develops when blood vessels have become severely blocked or damaged. In response, the body begins to produce new blood vessels - but these are often very weak and prone to bleeding, which can cause scarring to form. Leaked blood can also block light from reaching the retina, resulting in sight loss. Proliferative diabetic retinopathy can sometimes lead to retinal detachment, where the retina peels away from the back of the eye.

Diabetic maculopathy If these swellings worsen, blood vessels can begin to leak. Diabetic maculopathy occurs when leaking fluid has damaged the macula – a tiny collection of light-sensitive cells at the centre of the retina. The macula is crucial for central vision and seeing detail and colour, so macula-related sight loss can have a big impact. Not everybody with diabetes develops retinopathy. But it is one of the most common complications of the condition - and the longer you’ve had diabetes, the greater the chance of developing it.

Within 20 years of diagnosis, nearly everyone with diabetes will be affected to some degree. People whose diabetes is well managed are less likely to develop retinopathy than those whose blood sugar, blood pressure and cholesterol levels are poorly controlled.

Those who smoke are at higher risk. Proliferative diabetic retinopathy also tends to be more common in people with type 1 diabetes than type 2. And ethnicity can play a role: People of Afro-Caribbean and South Asian heritage are about twice as likely to develop sight-threatening diabetic retinopathy as white Europeans.

What are the signs and symptoms of diabetic retinopathy?

Vision isn’t usually affected during early stages of blood vessel damage. If the condition worsens, how it affects vision can vary from individual to individual. When diabetic retinopathy does cause symptoms, they may include: Reduced central vision.

This may be mild to begin with but can gradually worsen over time. Vision may become blurred and patchy, which might be most noticeable with tasks that involve seeing detail - like reading, watching TV and using a computer – due to damage affecting the macula.

Changes in colour perception. People may notice colours aren’t as clear and vibrant as they used to be. Floaters. An increase in floating shapes or dark spots in your field of vision can also occur. Eye pain. Diabetic retinopathy doesn’t always cause pain but any eye pain and/or redness should be assessed immediately, as it could be a sign of serious complications. Sudden severe sight loss or vision changes. Retinal detachment is a rare complication of diabetic retinopathy, but when it occurs symptoms can come on suddenly.

This may involve a dark ‘curtain’ moving across your field of vision, or a sudden dramatic increase in floaters or seeing flashing lights. Retinal detachment is a medical emergency that should be assessed urgently.

What can I do?

For anybody with diabetes, managing the condition well can help prevent problems including diabetic retinopathy from developing.

Alongside any medication when required, this involves following a healthy lifestyle with a balanced diet and regular exercise, not smoking, and monitoring blood sugar levels with the aim of keeping them stable. There’s lots of support available to help with managing diabetes - your GP can point you in the right direction.

Attending annual diabetic eye screenings is vital – the tests can detect early signs of damage before sight loss occurs. Regardless of when your last screening was however, if you notice any vision changes, it is always best to get things checked immediately. Any sudden or severe symptoms should be treated as a medical emergency.