Diabetic Eye Disease (retinopathy)

Diabetes mellitus, more commonly known as diabetes, is a condition of elevated blood sugar levels (hyperglycaemia) which can affect various organs, including the eyes. Blood sugar is controlled by the hormone insulin, which is produced in the pancreas.

There are two main types of diabetes:

• Type 1: results from a failure to produce adequate levels of insulin, often presenting in teenage years.
• Type 2: most common type due to development of a resistance to insulin, usually affects people over the age of 45yrs.

What is Diabetic retinopathy?

Diabetic retinopathy is the term used when the raised blood sugar damages the retina (image capturing tissue at the back of the eye). It is more common in type 1 compared to type2 diabetes, but overall affects approximately 80% of people with diabetes once they have had the condition for more than 10 years. Diabetic retinopathy is the commonest cause of severe sight impairment in the UK's working population.

There are different stages of diabetic retinopathy which can be broadly summarised as follows:

Background retinopathy
This is the earliest stage whereby high sugar levels weaken and damage the retinal blood vessels. Tiny bulges (called microaneurysms) occur in the blood vessel walls which can result in fluid (exudates) or blood (blot haemorrhages) leaking onto the retinal surface. This process often occurs "silently" and the patient is unaware, with no symptoms or change in vision. No specific treatment is required but patients are encouraged to be strict with their blood sugar monitoring and control.

Pre-proliferative retinopathy
Also known now as "non-proliferative retinopathy", there are more advanced signs in the retinal circulation, with visible changes in the blood vessels suggestive of a restricted blood flow to the eye. In milder cases no treatment to the eye is required but more frequent monitoring for new blood vessel growth (retinal neovascularisation) is recommended. Lifestyle changes can be important to reverse the retinal signs eg: balanced diet, regular exercise, blood pressure and blood sugar control. In severe cases laser treatment is applied to the retina to prevent new blood vessel growth.

Proliferative retinopathy
This arises when the damaged retina releases growth chemicals which encourage new retinal blood vessels to grow (retinal neovascularisation). Although this may initially seem like a helpful solution to improve the blood supply to the retina, the new vessels are thin and fragile. They tend to bleed easily and cause scar tissue, both of which can damage vision.

Laser photocoagulation is the main treatment for this condition. For reasons not fully understood laser can stop new retinal vessels from growing. Laser is focussed light energy which can seal blood vessels and stop leakage. It is usually applied in the out-patient department and often several sessions are needed.

Another newer approach to treat proliferative retinopathy is to block the chemical messengers which are responsible for the new blood vessel growth. One of the most important is the growth hormone Vascular Endothelial Growth Factor (VEGF). Anti-VEGF drugs eg: Avastin, Lucentis, which are already established treatments for macular degeneration (see AGE RELATED MACULAR DEGENERATION section), are currently being trialled for use in diabetic eye disease.

In very advanced cases of proliferative diabetic retinopathy bleeding can occur into the jelly of the eye resulting in sudden loss of vision = vitreous haemorrhage or scar shrinkage from leaking blood vessels can cause a retinal detachment. In both circumstances specialist vitreo-retinal surgery, usually a vitrectomy, is often required. Another very serious sign of advanced diabetic eye disease is the development of new blood vessels on the iris, at the front of the eye, which results in raised eye pressure = rubeotic glaucoma.

Diabetic maculopathy
The macular is the central part of the retina and is responsible for detailed central vision eg reading, recognising faces. The term diabetic maculopathy is used when this important area is affected, usually secondary to leaking retinal blood vessels. This "waterlogging" can occur silently without there being any symptoms or often the person affected will be aware of reduced vision in the eye.

Diabetic maculopathy can occur with any of the stages of retinopathy mentioned above ie background, pre-proliferative or proliferative retinopathy. Laser photocoagulation is the traditional treatment but anti-VEGF agents and steroids eg: Ozurdex - dexamethasone intravitreal implant, are also proving to be extremely useful.

Diabetic Retinopathy Screening and Prevention

There are several ways that people with diabetes can reduce their risk of developing sight threatening retinopathy:

• Healthy eating and regular physical activity.
• Careful monitoring of blood sugar, especially when unwell.
• Ensuring that blood pressure and cholesterol levels are optimised.
• Avoid smoking.
• Regular eye checks, especially if any change in vision.

Checking for diabetic retinopathy has become very much more standardised since the introduction of the NHS Diabetic Eye Screening Programme. This aims to reduce the risk of sight loss in people with diabetes by early detection and treatment. Although a national initiative the programme is delivered locally in line with set standards and protocols.

Everyone on a general practitioners database with a diagnosis of diabetes, over the age of 12yrs, is invited to attend annually for retinal screening. Pictures are taken which are looked at by photographers who have been trained to detect the signs of diabetic eye disease.

The local screening programme in this area is the South East Sussex Diabetic Retinopathy Screening Programme which is co-ordinated from Bexhill Hospital (www.esht.nhs.uk/retinopathy-screening). Anyone with diabetes will automatically be offered an annual screening photograph, often in a mobile unit near their home. The result is usually available within 4-6 weeks and if anything significant is detected the patient will be seen by an ophthalmologist in Eastbourne, Bexhill or the Conquest Hospitals.

Websites with useful information and support include:

www.diabetes.org.uk
www.diabeticretinopathy.org.uk
www.diabeticeye.screening.nhs.uk