To have poor eyesight; to be nearsighted or generally have weak vision.
彼は昔から目が悪くて、授業ではいつも眼鏡をかけている。
He's had poor eyesight since childhood and always wears glasses in class.
運転免許の更新で視力検査をしたら、目が悪いと言われた。
At the license renewal vision test they told me I have poor eyesight.
最近スマホを見すぎて目が悪くなった気がする。
Lately I've been looking at my phone too much and feel like my eyesight has worsened.