HI Sandie :)
Its not always easy with dogs, is it?!
I always feel any training aid which can, lets face it, be extremely scarey for a dog, should always be used as a last resort and preferably with experienced help. The thing is, as i'm sure you know, dog reactions can vary so much.
A friend tested the MasterPLus when her Japanese Spitz was several yards away, and the dog was terrified and wouldn't come backin the room all day. Another friend used it several times on her Flatcoat Retriever and he was only slightly phased (sp?) by it. The reactions vary so much, even within a breed.
ESS are bred to be mentally strong, and may for that reason, like the Flattie, cope well and be capable of learning from the experience. If a dog is very scared, the adrenalin will pump and it will not actually be capable of learning.
Most trainers use them in very controlled situations with set up "stooges" whether dogs or people. Many will also, for safety, start off on a long lead in case the dog is so scared it runs off. However there have also been a lot of people who have used them, as on the board here, with success, and both their lives and their dogs lives have been made all the better for theuse of the MasterPllus.
I haven't had cause to use the Aboistop, but as far as i know, it is not very good for lots of dogs together who may bark, as it can be set off by a dog other than the one wearing it, and that is definitely not fair

Regarding the dog with a sight problem, I personally would be in touch with a sympathetic trainer or behaviourist to assess the situation as a whole.
Best wishes
Lindsay