I have to say, I discovered that there was a 'raw' kind after trying the cheap kind. But as the supermarket one has worked perfectly I'll use it until its finished then look at buying the raw one as I'm sure it will benefit him in more ways than just clearing his eyes.

First I have heard of it so I did a little research. I must admit to being confused about references to "mother" and "raw", etc There does seem to be a general feeling that it is good for dogs but not those sensitive to yeast.

This is a definition of the type to buy.
The truly useful apple cider vinegar is not the clear vinegar you find in many stores. There's no health benefit from clear vinegar. The powerful benefits are found in the natural organic apple cider vinegar with a brownish tinge to it and floating stuff inside. The floating matter is called "mother" and is formed from the pectin and apple residue. This brown vinegar is the one creating all the buzz, the one with the minerals, amino acids and vitamins.

This site gives more info and advice
http://www.apple-cider-vinegar-benef.../pet-care.html

Thanks for the info Clarey.