Retinal nerve fibers enter the disc in three distinct manners. Other scotomas are produced, but these are the only ones we will be dealing with in this lab. This is the type of defect seen in glaucoma. A defect in this bundle results in a wedge-shaped temporal scotoma arising from the blind spot and does not necessarily respect the temporal horizontal meridian. Nerve fiber bundle defects originate from the blind spot and does not necessarily respect the temporal horizontal meridian.
Temporal fibers remain uncrossed and pass directly through to the ipsilateral optic tract.
Thus, a sagittal chiasmal lesion will cause a bitemporal hemianopia. The reason is that the chiasm rests upon the sella turcica and hypophyseal tumors or pituitary hypertrophy can translate pressure upward against the sagittal axis of the chiasm. And this is where the nasal fibers are located. Nasal defects have been correlated with sever artherosclerosis of the intracranial portion of the internal carotid artery. Recall from gross anatomy that the internal carotid passes very close to the lateral side of the chiasm.