The College of Optometrists

in diabetics how does the hemorrhages, exudates and cotton wool spots occur, what is actually happening in the reina? Im reading what the text books are saying but just want it in simple language, sorry and thanks

There's a good explanation in Kanski.

Basically in diabetics the blood vessels become fragile and leak both plasma and blood resulting in exudates and haemorrhages respectively. Cotton wool spots represent areas of ischemia in the retinal nerve fibre layer.

via microvascular occlusion (basement membrane thickens, platelets aggregate and RBC's change shape) leading to IRMA and neovasc. Capillary dilation results also due to these changes leading to exudates and haemorrhage. Kanski is good but that is the basis of what i am learning. Difficult to know how much detail they want !

For PQEs, at this stage of proceedings, jonesal2 is correct.

However, regarding cotton wool spots, as Steve Johns pointed out in a posting a few weeks ago (4/5/05), the idea that these are always caused by ischaemic infarcts to the retinal nerve fibre layer, though generally accepted by clinicians, has recently been questioned.

Just to add to jonesal2, the reason why the blood vessels become fragile is due to the loss of pericytes which cover the vessels and control the size of the blood column. I have heard an eminent speaker on the subject say that if you see one haemorrhage then every pericyte is dead in the retina.