Linux is a lot more friendly to people with reduced visibilty than Window$. It used to be that there were peripherals that didn't have Linux drivers, and things you just couldn't do, this is no longer the case. The only major difference is that Linux has far fewer games than Window$. It might be worth making the change just for the accessibility options. The most Windows-like distribution is Ubuntu, making the transition for what you are used to, to a new OS, easy. If you are a power user, you might prefer Mint. Only slightly less intuitive, but a bit faster.
All that being said, a bigger screen is the best option unless you travel a lot and therefore use a laptop (I have both). My eyesight is not that bad (slightly not-good-enough for driving) without correction, and I find a 22" screen to be fine. I need 2-dioptre reading glasses to read a mobile phone, but the desktop screen is both far enough away that I don't need reading glasses to read it, and close enough I don't need to wear my lenses.
I also have a projector and 4m x 3m screen for watching films. 1 kW 5.1 Dolby/dts sound system to go with it. I think that should be a big enough screen for anyone!
