Ok, time for some reality;
You guys know a lot more about pixels, noise and EV/ISO's (but I'm learning right here so thanks).
I am an eye surgeon who deals with this all the time so I will try to address most issues
The first sign of presbyopia is the loss of clarity when going from NEAR to FAR. Thus as someone noted earlier, they must look away from the finder and re-focus at distance to get "clear". While the effect is near universal, many don't do enough true near work (18" or less) to notice this earliest sign, but it is very reproducible in folks in their early forties. As folks approach their mid forties the near itself begins to be effected. This is normally attributed to the lens (not the cornea) stiffening, but it's just not that simple. If you actually remove lenses of folks that age you quickly realize that they are of differing rigidity depending upon the specimen. A more attractive model suggests simple crowding of the structures not allowing the muscles to pull as strongly (the lens grows throughout life). Anyone who lifts weights knows that a fully extended muscle can exert more power than a partially contracted one, has to do with molecular binding sites exposed, but unless you really want to get granular we'll stop there.
Note to all myopes; yes I know you take off your glasses to see up close, but these comments refer to everyone when corrected for distance whether by nature or man.
The effect is progressive as we age. Since the image in the optical viewfinder is actually a projection onto a mirror it is indeed a distance image, but unless you are old the correction necessary for near will only blur the image slightly. And has been noted things such as contrast sensitivity and secondary aberrations blur as well. An EVF is as looking at a TV and thus could be near, but I would suspect that manufacturers use correction to make it appear as a distance one, though I am not sure
As far as surgery, if you never wore glasses but it hit you in your 40-50 range it can be easily corrected with lasik. These are among my very happiest patients. As noted lens implant surgery can work well too but I do not recommend it for photographers since it will render you in focus at one point. Multifocal lenses are available but the decrement in distance is not tolerated by critical viewers in most cases. No one can make old eyes see as a young man however, time and gravity are cruel forces. We can make you better, but as yet cannot improve on Nature.
