The past century of advances in visual neurobiology
and perceptual science have all but passed visual hal-
lucinations by. Much of our assessment and management
owes more to 18th century Natural Philosophy than 21st
century Neuroscience. Part of the problem has been that
the experiences are traditionally considered rare, of poor
localising value and without associated morbidity.
However, recent recognition of their true prevalence
across a range of disorders
1-4
and the fact that they typi-
cally cause distress, are stigmatising, often inappropriate-
ly medicated and can precipitate institutional care, has
awakened research interest. Although much has yet to be
learnt, the basic and clinical science findings help formu-
late a structured approach to their assessment and man-
agement. What follows is a science-led guide to how one
might approach a patient presenting with visual halluci-
nations, either occurring
de novo
without previously
recognised pathology or, more typically, in the context of
ongoing neurological, ophthalmological or psychiatric
disease