Has Sclerotherapy ever caused Blindness? Or Vision Problems?

I have developed blue prominent temple veins, I know they can be treated with Sclerotherapy and I have read all about the concerns about Blindness and Vision Problems. My Questions: 1) Is this true and is it reported in the medical literature? 2) Can Sclerotherapy back flow to an artery? For this to happen the veins would have to be connected directly to the arteries? 3) Are the blue temple veins connect to the eyes? Do they flow into or drain from the eyes? Thank You.