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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. [7] [4] Other common symptoms are palinopsia, enhanced entoptic phenomena, photophobia, and tension headaches.
An example of the scintillating grid illusion. Dark dots seem to appear and disappear at intersections. The scintillating grid illusion is an optical illusion, discovered by E. and B. Lingelbach and M. Schrauf in 1994. [2] It is often considered a variation of the Hermann grid illusion but possesses different properties. [2] [3]
Purkinje's blue arcs are associated with the activity of the nerves sending signals from where a spot of light is focussed on the retina near the fovea to the optic disk. To see it, one needs to look at the right edge of a small red light in a dark room with the right eye (left eye closed) after dark-adapting for about 30 seconds; one should ...
Phosphenes have been created by electrical stimulation of the brain, reported by neurologist Otfrid Foerster as early as 1929. Brindley and Lewin (1968) inserted a matrix of stimulating electrodes directly into the visual cortex of a 52-year-old blind female, using small pulses of electricity to create phosphenes.
A retinal tear may also allow fluid to leak behind the retina, causing it to detach. This will often leak blood into the vitreous, which is seen by the patient as a sudden appearance of numerous small black dots or ribbons moving across the field of vision. Sometimes a gray curtain may appear to partially block vision in one eye.
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Lilac chaser: if the viewer focuses on the black cross in the center, the location of the disappearing dot appears green. Motion illusion : contrasting colors create the illusion of motion. Watercolor illusion : this shape's yellow and blue border create the illusion of the object being pale yellow rather than white [ 42 ]