I'm going to add just a bit to the last post. While there is lots of software out there that allows magnification, and it works beautifully, when it comes to significant macular degeneration the amount of magnification needed is very high. On any conventional monitor, including the largest ones designed as "real monitors," this means that only a small piece of the actual full-screen real estate is presented when magnification is on and you have to pan and scan in order to access things.
I can say from long experience, and even as a sighted person, that it is just so disorienting not to be able to take in the whole desktop (or whole program window) or something that is a very large swath of same at one time. This is why I have started going to whatever the appropriate size of HDTV that's needed to achieve "you can see the entire desktop" as the monitor of choice. Scanning with one's eyes, even if you have to get up very close to that screen and literally walk to get from side to side (and I've had clients that have to do this) is still more natural than trying to pan and scan on a small monitor with massive magnification in place. It's even often possible to avoid magnification entirely, as just presenting what would be on a 15" diagonal laptop screen or 20-something inch monitor blown up to large HDTV scale is enough.
If magnification is still needed, and it may be, the user needs to know how to toggle it on and off. Even if they can't read a Word document when it's off, there is often a need/desire to get a sense of how the thing would look on the printed page, which you don't get when you've got a lot of magnification going on. I'm working with someone now who has macular degeneration, but it's not really advanced (yet), who can still use a 20+ inch monitor but when using word is using the "page width" document view so that maximum magnification with retention of the entirety of a line across the screen is still there. But when she wants to get a sense of what the document would look like when printed, we go back to single page 100% zoom. She can't read it then, but she can tell how it lays out in paragraphs, etc., were it to be sent to the printer.
Regardless of how the magnification needed is achieved, knowing how to turn it on and off at will is an essential skill. Particularly if you're talking about a workplace with sighted coworkers, who are driven insane (and justly so) by huge magnification when you ask them to take a quick look at something.