Final answer:
Bitemporal hemianopsia affects the loss of the outer halves of the visual field in both eyes, typically due to a pituitary gland growth impacting the optic chiasm, affecting the axons that carry peripheral visual field information.
Step-by-step explanation:
Bitemporal hemianopsia is a condition affecting the eye in which there is a loss of the outer (temporal) halves of the visual field in both eyes. The optic nerves from both eyes meet at the optic chiasm where fibers are sorted. In the case of bitemporal hemianopsia, if there is a pituitary gland growth pressing against this optic chiasm, it interferes with the transmission of visual signals from the peripheral visual field, since the axons that decussate (cross over) at the chiasm carry information from the peripheral visual field contributed by the medial retinae. However, axons projecting from the lateral sides of the retina do not cross over and remain unaffected. This results in the loss of peripheral vision on both sides, causing the individual to lose sight of objects on their far right and left, while maintaining central and near-peripheral vision.