Just to be sure:
You lose your ability to crit when you lose an eye.
You get the ability to crit back (with +1cha and -1int) when you use Volos eye.
I guess it also works when you lost an eye because of the hag?
If you let Volo take your eye you lose the ability to crit even after he gives you the replacement eye. However if you steal the ete from him and "use" it you get a permanent +1 cha/-1 Int ability point adjustment but retain the ability to crit.
