can sympathise with your concerns but agree with previous post - the vet is there to answer your questions about this - don't hestitate to ring him/her. You get some great answers on here but on this, best speak with a real expert.I also have a blind dog and considered the same op for her - I decided against it though because one of the conditions was that she would have to stay on the lead for six months, not playing or shaking of the head if at all possible. She's a Border Coliie (going gradually blind due to cataracts, not diabetic so slightly different case to yours) and I thought that six months was a long time for out of a fourteen year olds life to be so restricted. Anyway, four years later she's still going strong and managing perfectly well although is virtually completely blind. Good luck.