This! Alternatively bike pogies. I have very bad circulation in my hands so these are a must for me. I often wear medium thick gloves AND use the bike pogies and my hands are OK, not great, but OK. The main thing the pogies do is keep the wind off of your hands.

Also, you may want to think about ski goggles. Eyelashes tend to freeze together at those temperatures. I've had my eyes freeze shut multiple times. That's not fun to deal with.

I've ridden in -40. It's not fun. Disk brakes aren't required when things get that cold/snowy. You won't be going fast enough to need them. (Going fast hurts cause of the wind.) Get an old mountain bike, get studded tires, I recommend nokian. (You can get $45 ones from REI, which will last you many, many seasons.) Don't bother trying to make your own, they don't work nearly as well. Commercially made tires give you at least 90% of the grip on glare (black) ice that you'd have with normal tires on dry asphalt. Get TWO, not one, TWO!!!! You may think "oh I can get away with one." NO, NO YOU CAN'T. I thought the same thing when I first started winter riding. Then I WATCHED my girlfriend wipe out hard, then I wiped out hard. (And I'm a freaking good rider.) Do yourself a favor and prevent an injury. Spend another 45 bucks and buy TWO tires.

If possible, when getting your old mountain bike, try to find one that can support WIDE tires. This isn't a necessity, my bike can only fit 1.95s. But, the wider the tire the better for going over small amounts of snow. (Alternatively, go skinny. Skinny tires cut straight through the snow and find the ice underneath.) Go to one extreme or the other, don't sit in the middle.

If you plan on riding on the road, then ride ON the road. Ride in the right tire track. Don't bother trying to ride in the gutter. It's even more dangerous. (Voice of experience.)

Think about LIGHTs. Days are very short in the winter and you'll often be riding in the dark. I recommend at least a 350 lumen front light (more is better) and a pretty decent rear light. One that you get behind and say "Damn, that's bright" and you have to avoid looking at it. The brighter the better. Also, buy a backup rear light. You don't want to lose a rear light due to you forgetting to charge it.

Is your bike being stored inside? It'd better be or plan to come out to a frozen bike every morning. Even if it's covered, it's likely that the derailleur will freeze in place and the cogs will become filled with snow/ice. Since you have vision problems, I'd think that they university would make an exception for allowing you to store your bike somewhere inside. Ask!

I enjoy riding in the winter. It certainly wakes you up. (And people give you crazy looks. AND you get the entire bike rack to yourself.) But you definitely need to be prepared. I actually ride longer than I have to in the winter. If I ride straight to work I never warm up and arrive freezing. If I take the longer way I'm nice and toasty by the time I get there.