I made the mistake of dropping a rat into a tub with a snake and walking away once. The snake was bitten through the eye ball, and on the cheek. The animal made a full recovery due to some steroid cream I got from my vet. You can barely tell he was ever bitten. His eye also seems to work, at least the pupil moves when I'm holding him. When it happened though it was bad. His eye was solid blue, and his face looked like it had been rubbed raw by sandpaper.

When you feed live prey you are taking a risk. The snake isn't always going to wrap it correctly and sometimes this will result in a bite. 9 times out of 10 the bite isn't very bad, but there are those times when your snake may need a vet visit. I would just be precautious and as other people stated, watch your animal until the rat/mouse stops moving. keep something long and metal in your hand in case you need it.

Other than that.. good luck.