be (as) blind as a bat

1. To be unable to see at all. After neglecting his vision for years, my grandfather became blind as a bat, unable to even see shadows. A: "Wasn't Emily blind as a bat after some sort of accident?" B: "Yeah, so she could leave town to search for a cure—typical soap opera story. They had to write her out somehow." Doc, I'll do anything—surgery, drugs, you name it! Anything to stop this before I'm blind as a bat.

2. To have poor vision. I've worn glasses for 20 years, so I'm as blind as a bat now. That's not a cat, it's a trashcan! Geez, you really are blind as a bat! Because I'm blind as a bat, I always knew there was a good chance my daughter would need glasses too.

3. To be oblivious to something. Are you blind as a bat? Those two have been flirting all afternoon! You must be as blind as a bat if you don't see the problem with this plan. Come on, I'm not blind as a bat. I know you two have been scheming behind my back this whole time.