I've heard that if your vision decreases while you're already a qualified pilot and it can be corrected to 20/20, then you can continue flying in some cases, but I think that would depend on what flying you were doing. And that might also have been in the past, rather than currently. I imagine having to use NV equipment makes it more of an issue. 

Obviously any kind of injuries that require regular physical therapy, or anything that affects your respiratory system could be an issue, as would anything that affects your nervous system or skeletal system - G forces and pressure on the skeleton, reflexes and co-ordination (especially hand-eye co-ordination) and keeping your body supplied with oxygen, as well as lung capacity are all vitally important parts of piloting, I'd say. 

And that's only physical injuries. Psychological ones are probably more common, and can be much more debilitating.