Katie,
 
I have met one completely blind ferret and have been caring for a
nearly-blind rescue, and neither seemed to notice their "impediment" or did
it slow them down much.
 
The completely blind one could get around a room just fine *and* use it's
litter box.  She wrestled, played tag, and even climbed tall objects.  No
problem.
 
The rescue I am caring for has cataracts and degerative retinal disease, so
in other words, he can barely see and is getting worse.  Near as I can tell,
he is about 4 years old and can see in a narrow field about a half inch in
front of his nose.  He walks slowly and methodically, and always "just
misses" running into things.  If he gets to excited and "trots" or runs, he
inveitably slams into somthing (not that it ever seems to bother him).  He
has little side vision, because it he is between two objects and gets
startled, he bangs his head when trying to glance at the sound.
 
This little guy has *no* fear of heights, and does wrestle with the
youngin's (though if he leaps to tackle one, he misses half the time...he
seems to base his leaps on the last known direction of the ferret he wants
to get, but since when do ferrets move in a straight line?).
 
Anywayz, point being that I have yet to see a disability, be it blindness,
missing limbs, paralysis, age, or anything else keep a ferret in otherwise
good health from having a fun, full life.
[Posted in FML issue 1566]