Charles Bonnet Syndrome and Other Hallucinatory Phenomena.

Descriptions of hallucinatory phenomena have figured prominently since the beginning of recorded history. Jean Etienne Esquirol (1772-1840) is usually credited for having introduced the term in 1817, differentiating between hallucinations and illusions. Both are wrong perceptions, but in illusions, an external stimulus is always present whereas hallucinations are perceptions that occur in the absence of corresponding sensory stimuli.