Light in the right eye gives no direct and no consensual response, but light in the left eye works. This is an afferent defect of the right eye, so the right optic nerve is damaged; the efferent CN III pathways to both pupils are intact.

• With a right oculomotor lesion, light in the right eye would still constrict the left pupil (consensual reflex preserved); only the right pupil would fail to constrict.