CLOSEDEYE HALLUCINATION

   Also known as closed-eye visual hallucination and closed-eye visualization. All three terms are used to denote a type of *visual hallucination experienced exclusively when the eyes are closed or when there is perfect darkness around. Some examples of phenomena classified as closed-eye hallucinations are * Eigengrau (i.e. a type of *visual noise), the *fiery rings of Purkinje, * hypnagogic and * hypnopompic hallucinations of a visual type, (some types of) * hallucinogen-induced * geometric hallucinations, and visual hallucinations occurring in the context of * sensory deprivation.Although Eigengrau and the fiery rings of Purkinje are classified more appropriately as *physiological illusions or * entoptic phenomena, they are commonly included in the group of closed-eye hallucinations as well. As to the pathophysiology of closed-eye hallucinations, a certain analogy has been suggested with the * Charles Bonnet syndrome, which is characterized by the occurrence of visual hallucinations in individuals with visual impairment. However, this analogy is debatable, if only because visual hallucinations occurring in the context of Charles Bonnet syndrome tend to come and go, whereas closed-eye hallucinations are often described as arising immediately upon eye closure, and lasting continuously until the eyes are opened. And yet in both cases the hallucinations at hand would seem to constitute * release phenomena. The notion of closed-eye hallucination should not be confused with the notions of * dream and * nightmare, or with the notion of * crepuscular hallucosis, which is reserved for hallucinatory states typically arising in halflight. Neither should it be confused with the * monocular hallucination, which can be stopped rather than provoked by the closing of an eye.

   References

   Eissa, A., Baker, R.A., Knight, J.L. (2005). Closed-eye visual hallucinations after coronary artery bypass grafting. Journal of Cardio-thoracic and Vascular Anesthesia, 19, 217-219.