Respectfully disagree for two reasons. 43mm is a so-called "normal" focal length because of its relationship to the diagonal of 35mm film. It has nothing to do with the field of human vision.
I'd say, shooting from the hip, that the human eye is like a 17mm lens [Edit: after asking Google, "what's the angle of view of a 17mm lens?" I would change this to 10mm or thereabouts] with a zoom feature for whatever has your attention. That is to say, the human eye as a lens system produces an image that your optic nerve can pick up, but it's your mind that decides what's important. So when you're reading, just the macula is involved, which is the central 2-3mm of cells in you optic nerve - kind of like a 100mm macro lens -- everything on the periphery drops away. However, when you are looking at a landscape and something moving at the periphery of your vision "captures" your attention it is waaaay out there in focal length terms. Something much more akin to the edges of a 17mm lens.
I approach this thinking about what your eyes evolved for: finding food (detail) and avoiding predators (wide). Those whose eyes weren't up to those two challenges had lives that were nasty, brutish, and short.
[Edit pace Hobbes' Leviathan, all lives were nasty brutish and short in the dim and distant past, at least up to a point. But nasti-er, more brutish and short-er for those whose eyes functioned like a 43 mm lens, which is what you'd get in the late stages of glaucoma.]
