[Sighted and blind in one person: a case report and conclusions on the psychoneurobiology of vision].

We present a patient with dissociative identity disorder (DID) who after 15 years of diagnosed cortical blindness gradually regained sight during psychotherapeutic treatment. At first only a few personality states regained vision, whereas others remained blind. This was confirmed by electrophysiological measurement, in which visual evoked potentials (VEP) were absent in the blind personality states but normal and stable in the seeing states. The switch between these states could happen momentarily. As a neural basis of such psychogenic blindness, we assume a top-down modulation of activity in the primary visual pathway, possibly at the level of the thalamus or the primary visual cortex. Therefore VEPs do not allow distinction of psychogenic blindness from organic disruption of the visual pathway. In summary, psychogenic blindness seems to suppress visual information at an early neural stage.