blind as a bat

Adjective

not-comparable

(simile) Nearly totally blind, having a very poor sense of vision

Japanese Meaning

極端に視力が悪い、ほぼ全く目が見えない状態 / 視力が非常に低い、ほとんど見えない

My grandfather is blind as a bat without his glasses.

祖父は眼鏡がないとほとんど目が見えません。

Sense（1）

(simile) Nearly totally blind, having a very poor sense of vision