Wernicke's signA physical sign demonstrating damage to the nerve pathways subserving vision. This commonly causes loss of half the field of vision in each eye. When a narrow beam of light is projected on to the blind half of one retina, the pupils do not constrict. Light shone on the normal half, however, causes the pupils to constrict.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005