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Closed-eye hallucinations and closed-eye visualizations (CEV) are hallucinations that occur when one's eyes are closed or when one is in a darkened room. They should not be confused with phosphenes, perceived light and shapes when pressure is applied to the eye's retina, or some other non-visual external cause stimulates the eye.
Visual snow syndrome (VSS) is an uncommon neurological condition in which the primary symptom is that affected individuals see persistent flickering white, black, transparent, or colored dots across the whole visual field.
The flicker fusion threshold, also known as critical flicker frequency or flicker fusion rate, is the frequency at which a flickering light appears steady to the average human observer. It is a concept studied in vision science , more specifically in the psychophysics of visual perception .
Many variations occur, but scintillating scotoma usually begins as a spot of flickering light near or in the center of the visual field, which prevents vision within the scotoma area. It typically affects both eyes, as it is not a problem specific to one eye. [5] [6] The affected area flickers but is not dark. It then gradually expands outward ...
The retina lines the inside of the eye. It is light-sensitive and communicates visual messages to the brain. If the retina detaches, it moves and shifts from its normal position. This can cause photopsia, but can also cause permanent vision loss. Medical attention is needed to prevent vision loss.
The visual effect is described as the loss of vision as the brain cuts off the unchanging signal from the eyes. The result is "seeing black", [citation needed] an apparent sense of blindness. A flickering ganzfeld causes geometrical patterns and colors to appear, and this is the working principle for mind machines and the dream machine.
Tscherning referred to this as the sixth image (the fifth image is formed by reflections from the anterior surfaces of the lens and cornea to form an image too far in front of the retina to be visible) and noted it was much fainter and best seen with a relaxed emmetropic eye. To see it, one must be in a dark room, with one eye closed; one must ...
As users adjust to the experience, they see increasingly complex animated yantra-like patterns of color behind their closed eyelids (similar effects may be seen when travelling as a passenger in a car or bus; close your eyes as the vehicle passes through the flickering shadows cast by regularly spaced roadside trees, streetlights or tunnel ...