A partial or total vision loss due to visual cortex abnormality or brain lesions. Other areas of the optical channel are not involved, and the eyes are healthy. However, the flow of visual information to the brain (visual cortex) is hampered. The condition can be congenital or acquired, and occasionally transient. The acquired disease is most often caused by loss of blood flow to the visual cortex from either ischemic stroke or cardiac surgery. The congenital disorder is most frequently a result of meningitis, encephalitis and perinatal ischemic stroke.