Cerebral injury from stroke or other trauma may cause visual imperception also called visual neglect, hemispatial agnosia, visual/spatial neglect, and hemi-imperception. It is a passive unconscious decreased awareness of part of the field of view or other stimuli to one side of the body. It usually occurs with a visual field defect, but may occur without loss of field.
A person without visual imperception, but with a visual field loss would still be aware of the area of loss and be more likely to make compensations. A person with both visual field loss and visual imperception would unconsciously neglect the area of the field loss and thus be less likely to compensate for the defect.
Damage to the right side of the brain may cause both visual field loss and visual imperception to the left side. Right brain injury neglect is usually more severe than left brain injury neglect. The most common site for visual imperception is the parietal lobe, but damage to frontal lobe and even the deeper structure (thalamus and basal ganglia) may cause visual imperception.
The treatment of visual imperception is still limited. It begins with teaching the patient to be aware of the neglected side often through occupational therapy. If the patient has a visual field defect, visual field awareness prism may be beneficial, followed by intense occupational therapy.
