Firstly I would take her into the garden on a lead so that you can prevent her bumping into things, also could you carry her to the field? Imagine if you were blind and try and guide her the way you would need to be guided. Sound will be so much more important to her, so keep talking all the time to let her know where you are. She needs to feel secure and things need to be kept in the same place (like chairs etc). Her water bowl needs to be offered to her on a regular basis to make sure she knows where it is.
I have a book on natural health for Dogs and Cats by Richard H. Pitcairn.
Under Cataracts it says to use a homeopathic remedy SILICEA 6X (6X is the strength of the tablet) give 1 or 2 tablets 4 times a day for several weeks.
He also says to use high doses of vitamin E.
Do not touch homeopathic tablets, tip them into the lid of the bottle and then into the dogs mouth, they are only tiny so there should not be a problem. Homeopathic remedies NEVER have any side effects, so are completely safe. They can be bought from most health food shops and are for humans and animals.
Hope this may be of some help, if you do not want to have your dog operated on I would definately try the homeopathic, you have nothing to loose (they cost about 5 pounds). Some results can be very quick, you do not have to give the tablets for ever, usually about a month, then again if the cataracts start to return.
Good luck (remember you are now her guide, take care of her).