[Historical approach to late visual hallucinations, from Charles Bonnet to Lewy body disease]

Charles Bonnet syndrome (CBS) was defined in 1936 by the Geneva neurologist Georges de Morsier (1894-1982) as "visual hallucinations occurring in elderly individuals while other brain functions remain intact," while emphasizing that "ocular lesions, which are common in the elderly, cannot be held responsible for these hallucinations." As will be shown, this definition evolved considerably over the course of the 20th century, and CBS is now generally understood as referring to "visual hallucinations associated with ocular disease." The history of this surprising nosological shift is examined through the original texts of Georges de Morsier, Jean Lhermitte, Henry Hécaen, Julian de Ajuriaguerra, Henri Ey, and others. This historical review of late-onset visual hallucinations (LVH)-that is, hallucinations occurring exclusively in elderly individuals (as opposed to those seen in psychotic disorders or delirium, which may occur at any age)-also provides an opportunity to discuss Lewy body dementia (LBD), a condition that remained poorly recognized until the late 20th century and in which hallucinations constitute a core clinical feature. The potential links between CBS and LBD are then explored.