How does diabetes affect the eye?
Over time, diabetes can affect the integrity of small blood vessels in various parts of the body – but especially in the eye, the kidney, and in the peripheral nervous system.
In the eye, diabetes can cause any one or more of the following:
- leakage of fluid at the macula (the part of the retina responsible for your central vision)
- deposition of proteins and lipids in the retina (known as exudates)
- loss of blood supply to the macula
- retinal haemorrhages
- retinal nerve fibre layer infarcts (“cotton wool spots”)
- growth of abnormal blood vessels
- vitreous haemorrhage
- secondary (rubeotic) glaucoma
Any of these conditions can lead to loss of vision – until recently, diabetes mellitus was the leading cause of blind registrations in the UK in adults under the age of 65 years.
All patients with diabetes need to have periodic retinal examinations, and the frequency of follow-up required will depend on the findings at initial examination.
What tests are available for diabetic retinopathy?
Colour fundus photography (see above) is helpful for documenting the state of the retina at any point in time. OCT scanning is helpful for diagnosing and monitoring macular swelling in diabetes. Fluorescein angiography (FFA) is helpful for delineating areas of loss of blood supply, assessing suitability for macular laser treatment, and looking for new abnormal blood vessels.
What treatment is available for diabetic eye disease?
New (abnormal) blood vessels growing on the retina (retinal neovascularisation) is usually treated with panretinal laser. This treatment causes regression of the abnormal vessels, reducing the chance that they will break and cause vitreous haemorrhage.
Diabetic macular oedema can be treated with any of the following three modalities:
- macular laser
- intravitreal injections of anti-VEGF
- intravitreal steroid implant
Each option has its own advantages and disadvantages and sometimes a combination of more than one treatment is chosen. This is a constantly evolving area and retinal specialists are often modifying their approach to managing this condition every several months, based on the latest data from large clinical trials.