I've tried several of the "visor" gadgets, without much luck. There seem to be two problems.
One - as somebody mentioned earlier, they create problems with regard to depth perception. I have particular trouble painting with a visor: I can't sense how far away from the model the brush is. (Some years ago I had an interesting conversation with the ship model restoration specialist at Mystic Seaport Maritime Museum. He used an Optivisor all the time. When I asked him how he dealt with the depth perception problem, he laughed and said, "I don't have a depth perception problem. I'm blind in one eye.")
Two - like most other 53-year-old human beings, I have two eyes that have deteriorated at different rates. So two identical lenses don't work for them.
A while back I happened to discover, at a Woodcraft store (also available online: <www.woodcraft.com>) a set of magnifying lenses that are made like clip-on sunglasses. They clip to the nosepiece of my regular eyeglasses and, when flipped down, add a magnification factor of +2. What a revelation! For me, at least, they work great - and cost about $15.00.
Youth, talent, hard work, and enthusiasm are no match for old age and treachery.