(as) blind as a bat
US /əz blaɪnd əz ə bæt/
UK /əz blaɪnd əz ə bæt/
1.
having very poor eyesight; unable to see well
:
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Without my glasses, I'm as blind as a bat.
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My grandmother is 90 years old and as blind as a bat, but she still loves to listen to audiobooks.