Blind drunk is a stage of drunkenness in which one is incapable of recognizing the persons and objects around onself. The blind drunk stage is a later stage of drunkenness that usually precedes the stage of passing out.
People often arrive at the passing out stage without experiencing the blind drunk stage at all.
Controlled scientific tests might, conceivably, show this to be related to fatigue - a fatigued person would succumb to alchohol and pass out before arriving at the blind drunk stage. On the other hand, such tests might also draw a connection between alcohol tolerance and the ability to become incoherent and visually impaired without first becoming unconscious. Consequently, blind drunkeness might be a state reserved for those who are well-rested, or it might be a state related to alcohol tolerance.