According to Lewis-Williams's theory, the enigmatic geometric shapes (entoptics
) evident in prehistoric rock art throughout the world indicate the first stage of altered states of consciousness as the shaman prepares to enter the spiritual or supernatural world (Lewis-Williams & Dowson 1989: 6063).
It is an entoptic
phenomenon, meaning that its source lies within the eye or visual system itself.
visualization of the retinal vasculature near fixation.
Dowson 1988 "The Signs of All Times Entoptic
Phenomena," Current Anthropology 29 (3):201-245.
Pearson might have mentioned the problems presented for his thesis by the Australian case, where entoptic
imagery abounds in rock-art, but trance and ASC-related shamanism is rarely observed in the ethnographic record.
phenomena in Upper Palaeolithic art," Current Anthropology 29 (1988): 201-245; Lewis Williams, D.
The blue field entoptic
phenomenon is produced by the different light absorption by erythrocytes and leukocytes when the retina is illuminated by blue light.
phenomenon, known as Haidinger's brush, was first described in the mid-1900s and is believed to be caused by xanthophyll pigments in the macular: lutein, zeaxanthin, and meso-zeaxanthin.
Her preposterously obsessive mark making seemed to signal an intention not merely to document the workings of the subconscious pictorially or textually, a la Surrealist dictates, but to register its entoptic
effusions in real time--a subtle shift toward a conception of drawing "as a verb." Indeed, one of the compelling things about these drawings is how they seem to be in dialogue not only with the ideas of the artists of Zurn's own generation but also with those of the generation that was just then coming of age.
Additionally, some authorities have included the presence of more basic hallucinations, such as spots, flashes of light and patterns, which are not attributable to entoptic
The healthy individual may sometimes notice physiological entoptic
phenomena, particularly peripheral flashes when viewing in very low illumination.
The two entoptic
phenomena strongly associated with the macular pigment are Haidinger's brushes and Maxwell's spot, both of which are only seen under highly specific experimental conditions.