Listen, bats in fact are not blind. That saying ''You're blind as a bat'' is not true. Bats have really good eyesight.

No, fruit bats are not blind.

most bats r blind blad. so blad bats are bling ennit bats r blind but blad som ain't ennit blind bats need to get ta Specksavers ennit blad cause if ya don't get there blad de bats will be blind ennit.

from GaNgStErBlAd ;P

When people saw bats fly into walls and/or narrowly miss them. People figured bats were blind and they were right. So whenever someone bumped into a wall, they said they were as blind as bats.

Yes! they have to because all bats are blind :)