Illusions, hallucinations, and visual snow

Clare L. Fraser*, Christian J. Lueck

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingChapterpeer-review

9 Citations (Scopus)


Illusions and hallucinations are commonly encountered in both daily life and clinical practice. In this chapter, we review definitions and possible underlying mechanisms of these phenomena and then review what is known about specific conditions that are associated with them, including ophthalmic causes, migraine, epilepsy, Parkinson's disease, and schizophrenia. We then discuss specific syndromes including the Charles Bonnet syndrome, visual snow syndrome, Alice in Wonderland syndrome, and peduncular hallucinosis. The scientific study of illusions and hallucinations has contributed significantly to our understanding of how eye and brain process vision and contribute to perception. Important concepts are the distinction between topologic and hodologic mechanisms underlying hallucinations and the involvement of attentional networks. This chapter examines the various ways in which pathological illusions and hallucinations might arise in relation to the phenomenology and known pathology of the various conditions associated with them.

Original languageEnglish
Title of host publicationNeurology of vision and visual disorders
EditorsJason J. S. Barton, Alexander Leff
Place of PublicationAmsterdam
Number of pages25
ISBN (Electronic)9780128213780
ISBN (Print)9780128213773
Publication statusPublished - Jan 2021
Externally publishedYes

Publication series

NameHandbook of Clinical Neurology
ISSN (Print)0072-9752
ISSN (Electronic)2212-4152


  • Alice in Wonderland syndrome
  • Charles Bonnet syndrome
  • Epilepsy
  • Hallucination
  • Illusion
  • Migraine
  • Parkinson's disease
  • Peduncular hallucinosis
  • Schizophrenia
  • Visual snow


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