What is the pathological process that causes diabetic retinopathy?

Having just read the question on why do type II diabetics get retinopathy more than type I, it caused me to remember this question. I have been unable to find a doctor who can explain exactly why high blood sugar actually causes retinopathy or microvascular damage.

I am sure there is probably a paper posted on this somewhere, but I would be grateful for an answer.

Authored By jacob matthews on Sunday 5th May 2013