I have some experience working as an editor for an author who needed voice-activated software. There are things an editor can do which are very simple for them but will make your tasks much easier.
Excellent suggestions, Ross, and probably the best advice offered yet.
I agree that you should prepare for eventually losing what little eyesight you have remaining. If it never happens, then you lose nothing, but if it does, you won't be left fumbling in the dark and despairing (which often happens when people lose their eyesight at an advanced age—they often NEVER recover—depending on others to take care of them).
If you have access to social services for visual impairments, they'll likely also have access to local or national access groups, so you can converse online with others in similar straits, so you can get firsthand knowledge about which techniques work and which don't (and also, which Social Service personal are worth a damn, and which AREN'T)!