Hemianoptic hallucinations

Hemianoptic hallucinations are visual hallucinations that occur when the third pair of cranial nerves is paralyzed, which is associated with impaired regulation of the rotation of the eyeballs up and down, as well as their lateral movement.

Most often, hallucinations are of a receptor nature. They are observed mainly in older people as a result of a progressive narrowing of the visual fields and is manifested by the loss of one half of the visual field of the opposite half of the visual cortex. Hallucinants are often directed towards the visual field defect. They are usually characterized by the sharpness of the hallucinated vision, brightness, color, clarity of the image, mobility of the object, shape, change in size. The hallucinated image can be distorted due to a violation of spatial and color synthesis; there are isolated hallucinatory images when the simultaneous participation of the central and peripheral parts of the visual analyzer is disrupted. Depending on the location of the defect, they are more often visible and perceived on the same half as truly visible. They appear suddenly or as associated with previous real images, are very rarely perceived as a subjective reflection of a true event, being under conscious control, patients exhibit an illusion of duality and an illusory displacement of both fields of vision, the reaction to light is the same, there is extensive damage to the central and peripheral parts of the visual system. The spatial localization of images on the retina does not change with eye movements. A feature of these hemianopsias is the stereoscopic perception of one object from both sides. The fundus of the eye is practically unchanged. The occurrence depends on the general condition of the nervous system and the degree of damage to the function of the cerebral cortex.