Closed-eye hallucination refers to the perception of patterns or images while one's eyes are shut. This phenomenon can be experienced during meditation, hypnosis, or as a result of sleep deprivation. Closed-eye hallucinations have various synonyms including phosphenes, closed-eye visuals, hypnagogic imagery, retinal phosphenes, and entoptic phenomena. Phosphenes refer to the sensation of seeing light without any external stimulation. Hypnagogic imagery is hallucinations experienced while falling asleep. Retinal phosphenes are caused by pressure on the eye, and entoptic phenomena are visual sensations produced by the eye itself. All of these terms are used to describe the different types of closed-eye hallucinations experienced by individuals.