CN II Pathology
Prechiasmatic lesions which include fractures of sphenoid bone (transecting the optic nerve), retinal tumors, or masses compressing the optic nerve result in unilateral blindness and unilaterally unreactive pupil (although the pupil would react with light shown in the contralateral eye). Bitemporal hemianopsia (tunnel vision) can be caused by pituitary adenoma, craniopharyngioma or saccular Berry aneurysm at optic chiasm. Postchiasmatic lesions are associated with homonymous hemianopsia or quadrantanopsia depending on location of the lesion.