Diabetic retinopathy is the real medical term for diabetic eye disease and is the most common cause of blindness in people of working age with 94 million people affected worldwide – but what causes it?
Although diabetes is a serious cause of eye disease, less than 5% of patients with diabetes suffer from severe visual loss due to their diabetes. Diabetic retinopathy is found in 77.3% of those with type-1 diabetes, and 25.1% of those with type-2 diabetes.
After 15 years of type-1 diabetes, 98% will have some form of diabetic eye disease. In type-2 diabetes, this applies to 78%.
What causes Diabetic retinopathy?
In diabetes, hyperglycaemia (high blood glucose levels) causes increased retinal inflammation, such that the small blood vessels of the retina (back of the eye) become dilated and leak tissue fluid into the back of the eye. New blood vessels start to grow which ordinarily should not be there. Blood vessels may become blocked with tiny blood clots, disrupting the retinal blood supply.
Increased oxidative stress (the metabolic processes that produce oxygen) results in larger numbers of dangerous molecules called reactive oxygen species (ROS) in the retina. These can also damage DNA.
Advanced glycation end products (AEGs) – large molecules formed from fat, sugar and protein becoming stuck together found in the bloodstream – further exacerbate local inflammation, causing damage to the extracellular matrix (connective tissue).
Eventually, fibrosis (scar tissue) is formed in the eye increasing the risk of serious complications such as retinal detachment.
What are the symptoms of Diabetic eye disease?
- Blurred vision
- Double vision
- Pain in the eye
- Vision is dim – as if you were always wearing sunglasses
- Poor colour vision
- Having dark areas of vision or visual loss
- Seeing flashes of light
Other risk factors to consider
Other risk factors for diabetic eye disease are:
- High blood pressure
- Protein in the urine
- Raised cholesterol
What does it look like?
When the pupils are dilated and the retina is examined, the typical findings are –
- Venous changes – capillaries may be looping, beaded, or dilated
- Arterial changes – small arteries may appear narrowed, or as ‘silver wiring’
- New vessels may grow on or near the optic disc
- Cotton wool spots – soft exudates
- Hard exudates – yellow patches
- Retinal haemorrhages – superficial, flame-shaped, or dot and blot
- Microaneurysms – tiny outpouchings in the arteries or veins of the retina
Diabetic eye disease may be classed as mild, moderate or severe. It is also either proliferative or non-proliferative. In advanced disease, there may be macular oedema (swelling).
Diabetic eye disease increases the risk of cataracts and glaucoma.
When is diabetic eye screening recommended?
In type-1 diabetes, diabetic eye screening is recommended 5 years after diagnosis, and once a year after this, for life. In type-2 diabetes patients should be screened at diagnosis and once a year after this, for life.
During pregnancy, women with type-1 and type-2 diabetes should have an eye examination within 3 months of becoming pregnant, probably again during the pregnancy, and for follow-up after giving birth. If women have gestational diabetes (diabetes that develops in pregnancy) they don’t normally need an eye examination as diabetes disappears when the pregnancy has ended.
Early diagnosis, proper treatment and follow-up are mandatory. If diabetes is not well controlled, this is likely to worsen the prognosis of diabetic eye disease. Optimal management of diabetes is crucial to preserve good eyesight. It’s vital to try and obtain an HbA1C level (a marker of how much glucose is stuck to your haemoglobin) of less than 7%.
How long does it take diabetic eye disease to develop?
Eye specialists state that diabetic eye disease takes 5 to 15 years to develop. In those with type-2 diabetes, their diabetes may have gone undetected for a long time before it was diagnosed, and therefore the patient should have an eye check at the time the diagnosis of diabetes is made. However, type-1 diabetes is diagnosed soon after a sudden onset, and so the patient can wait 5 years before needing to have an eye check.
Diabetic patients need to understand that working hard to get the best blood glucose control will reap benefits for their eyes and their vision in the long term.
How to prevent diabetic retinopathy
- Manage your diabetes effectively
- For type-2 diabetes your premeal blood glucose should be between 4-7 mmol/L. 90 minutes after a meal it should still be less than 8.5 mmol/L.
- Keep your blood pressure under control
- Take any blood pressure medication you have been prescribed perfectly – don’t skip doses. Consider purchasing a blood pressure machine and take regular readings at home to show your GP. Patients with diabetes should not have a blood pressure of over 140/80 mm Hg.
- Lower your cholesterol
- Take any cholesterol-lowering medication as prescribed. Eat a diet low in saturated fat. Your cholesterol should be no more than 4 mmol/L.
- Other lifestyle factors
- These are also very important. You need to eat a healthy, well-balanced diet, to ensure you get an adequate intake of vitamins and minerals, all vital for the health of your eyes. Take regular exercise – at least 150 minutes of moderate-intensity exercise per week.
- Don’t smoke
- Don’t drink more than the recommended 14 units of alcohol per week
- Although most studies do not show a direct link between alcohol and diabetic retinopathy, excess alcohol is associated with a reduction in visual acuity.
- Make sure you always attend your clinic appointments
- And follow the advice you are given carefully. Even if you think there is nothing wrong with your vision, you should still make sure you attend your diabetic eye screening appointment.
- If you notice any changes to your vision, go for help straight away
- Don’t leave it.
For more information
- Diabetes UK – Diabetes and eye problems (diabetic retinopathy)
- NHS –Prevention – Diabetic retinopathy
This piece was written and provided by Dr Deborah Lee, Dr Fox Online Pharmacy.