Dominic H ffytche1. 1. Section of Old Age Psychiatry and Centre for Neuroimaging Sciences, Institute of Psychiatry, King's College London, London, UK. d.ffytche@iop.kcl.ac.uk
Abstract
PURPOSE OF REVIEW: The literature related to visual hallucinations in ophthalmological settings from 2007 to 2008 is presented as a review of recent developments and trends. RECENT FINDINGS: Acuity, contrast sensitivity, age and sex emerge as significant and consistent risk factors for visual hallucinations, together with new evidence to suggest that up to 40% of patients have long-term hallucinations. Scotoma size and specific eye pathology do not influence hallucination risk. Induced hallucinations in normal individuals provide a model for those in eye disease, revealing a shift in thalamocortical circuitry and neurophysiological links to states of drowsy wakefulness. Serotonergic therapy emerges as a potential treatment. Two ophthalmological interventions are added to the list of procedures provoking hallucinations. Historical accounts of Charles Bonnet, his syndrome and two novel visual syndromes highlight ongoing difficulties of case definition and the wider clinical context in which visual hallucinations occur. SUMMARY: Current research into visual hallucination is predominantly ophthalmology-led, with increasing recognition of the phenomena, their prevalence and prognosis within the specialty. Deafferentation remains the best available pathophysiological account, although it fails to explain the absence of hallucinations in the majority of patients with eye disease. Whether hallucinations require treatment and, if so, what that treatment should be remains unclear.
PURPOSE OF REVIEW: The literature related to visual hallucinations in ophthalmological settings from 2007 to 2008 is presented as a review of recent developments and trends. RECENT FINDINGS: Acuity, contrast sensitivity, age and sex emerge as significant and consistent risk factors for visual hallucinations, together with new evidence to suggest that up to 40% of patients have long-term hallucinations. Scotoma size and specific eye pathology do not influence hallucination risk. Induced hallucinations in normal individuals provide a model for those in eye disease, revealing a shift in thalamocortical circuitry and neurophysiological links to states of drowsy wakefulness. Serotonergic therapy emerges as a potential treatment. Two ophthalmological interventions are added to the list of procedures provoking hallucinations. Historical accounts of Charles Bonnet, his syndrome and two novel visual syndromes highlight ongoing difficulties of case definition and the wider clinical context in which visual hallucinations occur. SUMMARY: Current research into visual hallucination is predominantly ophthalmology-led, with increasing recognition of the phenomena, their prevalence and prognosis within the specialty. Deafferentation remains the best available pathophysiological account, although it fails to explain the absence of hallucinations in the majority of patients with eye disease. Whether hallucinations require treatment and, if so, what that treatment should be remains unclear.
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