The term neurological visual impairment (NVI) covers both CVI and total cortical blindness.
The major causes of CVI are as follows: asphyxia, hypoxia (a lack of sufficient oxygen in the body's blood cells), or ischemia (not enough blood supply to the brain), all of which may occur during the birth process; developmental brain defects; head injury; hydrocephalus (when the cerebrospinal fluid does not circulate properly around the brain, and collects in the head, putting pressure on the brain); a stroke involving the occipital lobe; and infections of the central nervous system, such as meningitis and encephalitis.
A diagnosis is usually made when visual performance is poor but it is not possible to explain this from an eye examination.
Before CVI was widely known among professionals, some would conclude that the patient was faking their problems or had for some reason engaged in self-deception.
However, there are now testing techniques that do not depend on the patient's words and actions, such as fMRI scanning, or the use of electrodes to detect responses to stimuli in both the retina and the brain.