Cerebral polyopia

Cerebral diplopia or polyopia describes seeing two or more images arranged in ordered rows and columns after fixation on a stimulus.^[1] The polyopic images occur monocular bilaterally (one eye open on both sides) and binocularly (both eyes open), differentiating it from ocular diplopia or polyopia. The number of duplicated images ranges from one to hundreds. Some patients report difficulty in distinguishing the replicated images from the real images, while others report that the false images differ in size, intensity, or color.^[1] Cerebral polyopia is sometimes confused with palinopsia (visual trailing), although in cerebral polyopia, the duplicated images are of a stationary object. Movement of the original object causes all of the duplicated images to move, or the polyopic images disappear during motion.^[2] In palinoptic polyopia, movement causes each polyopic image to leave an image in its wake, creating hundreds of persistent images (entomopia).^[2][3]

Infarctions, tumors, multiple sclerosis, trauma, encephalitis, migraines, and seizures have been reported to cause cerebral polyopia.^[1][4] Cerebral polyopia has been reported in a extrastriate visual cortex lesions, which is important for detecting motion, orientation, direction, and motion.^[1] Cerebral polyopia often occurs in homoynous field deficits,^[5] suggesting deafferentation hyperexcitability could be a possible mechanism, similar to visual release hallucinations (Charles Bonnet syndrome).

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