Vision threatening diabetic eye disease

In this video Dr Consuela Moorman, consultant ophthalmologist with the Oxford University Hospital Trust, UK, considers the diabetes related changes in the eye which can lead to vision loss. She also introduces the International clinical disease severity scale for Diabetic Retinopathy and Diabetic Macular Oedema, which provides guidance to eye health professionals on when to intervene with treatment to reduce the risk of vision loss.

Managing eye complications needs the attention and understanding of both the person with diabetes and the eye health professional. As you watch the video and read the infographic below, consider the key educational message/s that need to be given to people with diabetes about their eyes and diabetes.

Infographic: How diabetes affects the eye

You can download and use this simplified diagram to explain how diabetes affects the eye to people with diabetes who are at risk of visual loss.

(Click to expand) or (Download as PDF)

• MICROANEURYSM– small deep red dots in the retina (not haemorrhages) but as “out-pouches” from damaged or weakened capillary walls. They may or may not be leaking
• HARD EXUDATE– distinct yellow white deposits of lipids that have leaked from damaged retinal capillaries. They can be seen as small deposits, larger plagues or in distinct circinate pattern around the macular
• HAEMORRHAGES– intraretinal bleeding may be ‘dot’, ‘blot’ or ‘flame’ shaped depending on their depth within the retina
• COTTON WOOL SPOTS– greyish white fluffy patches of discolouration in the nerve fiber layer, linked with focal hypoxia and swelling of nerve fibres
• MACULAR OEDEMA – swelling at the macular caused by leakage and build of fluid into the retina, affecting vision
• VEGF – Vascular Endothelial Growth Factor. Stimulates the growth of new blood vessels
• NEOVASCULARISATION– abnormal and fragile new blood vessel growth on the retinal surface, which can bleed easily, affecting vision.

Diabetes leads to high blood sugars (hyperglycaemia) in the body. Hyperglycaemia triggers a wide range of biochemical changes within the body’s cells that can lead to:

• Swelling and shrinking due to changes in water content within cells (osmotic changes)
• Cell damage or even cell death due to imbalances between production of free radicals and antioxidants to limit damage (oxidative changes or oxidative stress)
• An inflammatory response

All these wide ranging biochemical changes due to hyperglycaemia can lead to structural and functional changes throughout the body, including the eye.

In the anterior segment (front) of the eye, osmotic and inflammatory changes can cause corneal epithelial damage, changes in refraction and early development of cataracts.

In the posterior segment (back) of the eye, microvascular changes can lead to:

• Increased leakage from damaged capillaries. The capillary cell wall can be weakened, which leads to development of microaneurysms, or increased leakage of lipids causing hard exudate deposits, break open and cause dot and blot haemorrhages. At the macula the leakage can be extensive causing swelling (macular oedema), directly affecting vision.

• Blockage of the capillaries can be due to a number of factors such as thickening of the basement membrane in the wall of the capillary, increased “stickiness” of platelets, changes in red blood cells. Blockages to the flow of blood in the retina leads to a loss of oxygen (hypoxia), affecting the function of the nerve fiber layers and photoreceptors. We observe these areas of hypoxia in the retina as cotton wool spots. Tissues that are low in oxygen trigger the release of vasucular endothelial growth factors (VEGF) which in turn cause new (but abnormal) vessels to grow (neovascularisation) on the surface of the retina. These can break and leak easily causing a range of complications from haemorrhages, retinal detachments and visual loss.