My primary interest is sailing ship models, and I was lucky enough to be born with a priceless asset for that sort of work: nearsightedness. Without my glasses I have trouble recognizing my wife from across a room, but until recently I was able to do all my modeling work without magnification. (At the maritime museum where I used to work, people teased me a little because I took my glasses off whenever I got near a model.) I just turned 55, though, and during the past few years I've been finding it difficult (without glasses) to focus both eyes at the same, relatively close distance. I have two pairs of glasses - bifocal and single-vision. I ordinarily use the bifocals, but I find them clumsy for model building.
I've never been able to get along with magnifying visors, for two reasons. First, they destroy my depth perception. That's especially problematic in detail painting. With an Optivisor my eyes tell me the brush is considerably farther away from the part I'm painting than it actually is. (I had an interesting conversation about this once with a professional ship modeler at Mystic Seaport Maritime Museum. I noticed he was using an optivisor, and asked him how he managed without losing his depth perception. He laughed and explained that he'd been born blind in one eye. So he was accustomed to judging distances without binocular vision.)
My other problem with visors is that my eyes, like those of most human beings, are different from each other. Since both lenses in a visor have the same amount of correction, the best they can do is to let me focus one eye on the model. I guess I could wear the single-vision glasses under the visor, but that gets awkward.
The best solution I've found is a simple and reasonably cheap one. At the Woodcraft woodworking supply company I found, for $15.50, a pair of magnifying lenses that are made like flip-up sunglasses. They clip onto my single-vision glasses, and flip up out of the way when I don't need them. The first time I used them on a model project I was hooked. The single-vision glasses let both eyes focus at the same distance, and the magnifiers magnify the entire field of view (rather than just the bottom, like bifocals do).
Here's the link: http://www.woodcraft.com/family.aspx?familyid=4511
By the way, if you click on that link you'll find it worthwhile to browse around the Woodcraft site. The company sells all sorts of stuff that's useful for model building.
Youth, talent, hard work, and enthusiasm are no match for old age and treachery.