Visual Hallucinations

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Simple Visual Hallucinations

  • Perception of simple ‘positive’ visual phenomena, without corresponding real objects, including:
    • White or coloured flashes/sparks
    • Zig-zag patterns
    • “Visual snow” = pixelated vision; affects both eyes, entire image / visual field
  • Causes
    • Posterior vitreous detachment or retinal detachment
    • Compressive optic neuropathy
    • Migraine aura
    • Occipital lobe tumour, epilepsy, infarct, or arterio-venous malformation
    • Idiopathic, e.g., “visual snow”

Complex Visual Hallucinations

  • Perception of complex ‘positive’ visual phenomena, without corresponding real objects, including:
    • Seeing animals, objects, or people that are not present
  • Causes
    • Dementia
    • Drugs, medications
    • Occipital tumor
    • Complex focal epilepsy/occipital lobe epilepsy
    • Bilateral blindness -> Charles Bonnet Syndrome = Occipital brain syndrome (in conscious, non-psychiatrically ill individuals -> assure patients they are not going insane)


  • EyeWiki Different Types of Visual Hallucination
  • The Wills Eye Manual: Office and Emergency Room Diagnosis and Treatment of Eye Disease; Kalla Gervasio MD, Travis Peck MD et al; Lippincott Williams&Wilkins; 8th Edition (2021)
  • Kanski‚Äôs Clinical Ophthalmology: A Systematic Approach; John E Salmon MD; Elsevier; 9th Edition (2019)