Right click the desktop and select Personalize. From there click on the Color and Appearance section. there you will see at the bottom Advanced Appearance Settings. Click that.
This will bring up this window:
There you can go through each of the options in the Items drop down menu and ajust the size manually for the best appearance on the recommended resolution of the monitor.
So you could still use the monitor recommended resolution but customize the theme itself to show larger text and everything so that the person with poor eyesight can still see everything with ease while not using a low resolution.