The word "blear" is often used in relation to visual perception, but it can also extend to describe situations, sounds, or atmospheres that are unclear or lacking in sharpness. Its use to describe tired eyes—often associated with illness or lack of sleep—has permeated both everyday language and literary expressions.
The term "blear-eyed" remains a strong idiomatic expression to describe someone who has been awake for too long or is physically drained. "Blear" is not a word often used in casual conversation but is more prevalent in literary or descriptive writing, particularly when trying to evoke an atmosphere of exhaustion or blurriness, either literal or figurative.