ABSTRACT

The optic tracts sweep laterally from the optic chiasm, passing around the ventral portion of the midbrain and encircling the hypothalamus posteriorly. Each optic tract contains crossed nasal retinal fibres that originate in the contralateral nasal hemiretina and uncrossed temporal retinal fibres that originate in the ipsilateral temporal hemiretina. Optic tract defects result from lesions of the optic tract that are similar to those causing damage to the optic chiasm. Meningiomas that involve the optic tract may arise from the tuberculum sellae or lesser wing of sphenoid and are slow growing. A lesion of the optic tract may damage the ipsilateral cerebral peduncle and give rise to mild contralateral pyramidal signs. Partial lesions of the optic tract will cause partial contralateral homonymous visual field defects but the incomplete pairing of the retinal nerve fibres of the two eyes results in incongruity. Pituitary tumours may compress the optic tract first at an antero-infero level, resulting in homonymous defects.