Diabetic retinopathy: how high blood sugar levels affect the retina

Diabetic retinopathy is an eye condition in which progressive damage occurs to the retina of people with diabetes.

Mr Bhaskar Gupta, highly qualified consultant ophthalmologist who specialises in diabetic retinopathy, provides an expert insight into the condition, explaining stages, signs and treatment.

What is diabetic retinopathy?

Diabetic retinopathy is a condition which affects the retina. In simple terms, diabetes is a systemic condition that can cause the leaking of blood vessels all over the body. The retina, on the other hand, is similar to a photographic film at the back of the eye which helps to process signals and send them to the brain. When we see signs of damage to these photographic films from a systemic condition called diabetes, this is called diabetic retinopathy.

What are the four stages of this condition?

The stages of diabetic retinopathy can sometimes be very confusing in literature. People use different terminologies: ETDRS used mainly for academic and research purposes, modified ETDRS for clinical purposes, Diabetic Screening Services etc. However, one way to look at diabetic retinopathy is by dividing the condition into four simple stages.

The first stage is mild, where there are some early changes of diabetes in the retina, like small leaking blood vessels. Most patients at this stage are completely asymptomatic and often, these leaking blood vessels will be accidentally picked up when you go for a routine optician check.

The next stage is more moderate: it could still be asymptomatic, but you will see more lot more haemorrhages in the retina, tortuous or dilated blood vessels in more than one quadrant of the retina. These changes can occur in combination or isolation to each other.

The third stage is severe, where you see a combination of at least two signs seen in the moderate stage. This is a pre-stage to a severe or a proliferative disease, which is the fourth stage of diabetic retinopathy.

In the proliferative stage, there is a spread of new blood vessels into the retina, which are produced as a response to the shutdown of the natural capillaries from diabetes. These shutdown capillaries release a special chemical, called a vascular endothelial growth factor (VEGF), that causes the sprouting of new blood vessels. As these are new blood vessels, they do not have the same architecture as the blood vessels that you are born with, they do not have the same strength and they tend to bleed easily into the eye and into the retina, causing severe and significant loss of eyesight.

Apart from retinopathy, another change identified in diabetes is maculopathy. Macula is the specialised area in the centre of the retina that helps us to see clearly both in distance and near, gives colours and contrasts vision. The rest of the retina provides peripheral field of vision. When there is a leakage of fluid in the macula, you may be aware of blurriness or distortion. This can cause symptoms.

Blurring of vision in patients with diabetic retinopathy is either from maculopathy or retinopathy. Maculopathy can occur independent to any stages of retinopathy.

What are the signs and symptoms that people should look out for? Are they apparent in the early stages?

Diabetes is quite often asymptomatic, especially Type 2 diabetes that is seen in the later half of life. As a result, most people are diabetic five to seven years before they have an official diagnosis of diabetes.

On another note, eye symptoms are accidentally picked up by your optician when you go for a routine check. Sometimes, people will be aware that they are struggling with the clarity of their vision or their lack of focus. Usually, one eye will be more affected, but because we use both eyes, one eye will compensate for the other. Unless you accidentally cover one eye to notice that it is affected, you will not be aware of the symptoms.

Some of the changes of diabetic retinopathy, especially mild and moderate, are reversible in the early stages. The key aspect to diabetes and its management in relation to the eye is to have a good, well-controlled diabetes so that your sugar levels (mainly the HBA1BC, which is the reflection of three months errors of diabetes control) are close to four or five. However, this also depends on the scales being used.

Equally important are other risk factors, which are blood pressure and cholesterol. Together, they can cause significant sight loss – but these are modifiable risk factors. What is not modifiable in diabetes and in diabetic retinopathy, is the duration of diabetes. However, if we are proactive, we keep a good diabetic control and we keep a very good control of blood pressure and cholesterol, we can significantly delay the progression and the severity of diabetic retinopathy.

What is the aim of treatment for diabetic retinopathy?

The treatment for diabetic retinopathy has evolved significantly in the last 15 years with the advent of anti-VEGF injections (anti-vascular endothelial growth factor injections) in addition to new lasers, which could stabilise the retina and the damage to the retina from diabetic retinopathy. Most people now can continue to drive after laser treatment and sometimes, in combination with anti-VEGF injections.

Very importantly, once you are diagnosed with diabetes, your GP will refer you to a diabetic eye screen programme, which is run nationally. It is advisable that you attend these regularly. Initially, the screening is every 12 months unless you see signs of diabetic retinopathy. Once there are signs which could affect vision, you will then be referred to secondary care for further observation and management, if needed.

How should people manage diabetic retinopathy alongside their treatment?

The two main treatment modalities for managing diabetic retinopathy are anti-VEGF injections and lasers. There is no one treatment for all; frequently, a combination of treatments is needed to keep the vision stable. We also now have newer anti-VEGF injections approved and licensed which require less frequent injections and can give you good, long-term stable vision.

Mr Bhaskar Gupta is a highly qualified consultant ophthalmologist who specialises specifically in diabetic retinopathy, offering both laser treatments and anti-VEGF injections. If you have diabetic retinopathy and wish to consider your options, don’t hesitate to visit Mr Gupta’s Top Doctors profile today.