C. Cotton wool spots – Explanation
Cotton wool spots are seen in pre-proliferative retinopathy
Diabetic retinopathy
Diabetic retinopathy is the most common cause of blindness in adults aged 35-65 years-old.
Hyperglycaemia is thought to cause increased retinal blood flow and abnormal metabolism in the
retinal vessel walls. This precipitates damage to endothelial cells and pericytes
Endothelial dysfunction leads to increased vascular permeability which causes the characteristic
exudates seen on fundoscopy. Pericyte dysfunction predisposes to the formation of
microaneurysms. Neovasculization is thought to be caused by the production of growth factors in
response to retinal ischaemia
In exams you are most likely to be asked about the characteristic features of the various
stages/types of diabetic retinopathy. Recently a new classification system has been proposed,
dividing patients into those with nonproliferative
diabetic retinopathy (NPDR) and those with proliferative retinopathy (PDR):
| Traditional classification | New classification |
Background retinopathy
|
Mild NPDR
|
Proliferative retinopathy
- retinal neovascularisation – may lead to vitrous haemorrhage
- fibrous tissue forming anterior to retinal disc
- more common in Type I DM, 50% blind in 5 years
Maculopathy
- based on location rather than severity, anything is potentially serious
- hard exudates and other ‘background’ changes on macula
- check visual acuity
- more common in Type II DM
