Yes, you can get diopters for the camera, just take one out and slip another one in.
Of course, being possible and available are different things. I know the focussing screens that are interchangeable also work in the current digital models (I've got an EC-Civ from a 1Dmk4 in my EOS 3 at the moment).
But for diopters, I don't know if what fits the EOS 3 will fit the current digitals (and hence be readily available), or if you'll have to go scouring fleabay etc. If noone answers this within a few hours I'll check my user manual when I get home from work.
Then of course you'd have to take your glasses off to use the camera.
Also, make sure you clear the calibration from the last user (if you got it second-hand like I did), just adding points to a massive dataset that already exists isn't going to help much.