expression
sitting up all night; staying up all night
Idiomatic phrase describing staying awake through the night, often with a sense of effort or vigilance. Used adverbially with verbs like 働く, 看病する, or 勉強する.
試験前は夜の目も寝ずに勉強した。
Before the exam, I studied all night without sleeping.
看護師は夜の目も寝ずに患者の世話をした。
The nurse stayed up all night caring for the patient.
寝ずの番 refers specifically to staying awake to keep watch, whereas 夜の目も寝ず is broader and can apply to any all-night activity.
A fixed expression combining 夜 (night), 目 (eye), も (even), and 寝ず (negative continuative of 寝る, 'to sleep'), literally 'without even the eyes sleeping at night'. The exact origin is uncertain, but it is a traditional idiomatic phrase.