Final answer:
The student's question is correctly answered by 'c. both a and b', as the optic nerve's proximity to the pituitary gland can lead to vision problems like bilateral hemianopia when a tumor compresses the optic chiasm.
Step-by-step explanation:
The correct response to the student's question is c. both a and b. Due to the close proximity of the optic nerve to the pituitary gland, it is not unusual for patients with pituitary tumors to present with vision issues. The pituitary gland is located in the sella turcica of the sphenoid bone, just beneath the optic chiasm, where the optic nerves intersect. A pituitary tumor can cause a unique clinical presentation known as bilateral hemianopia, which is the loss of lateral peripheral vision. In this condition, a patient's central vision remains intact, but they lose the ability to see objects to their right and left, due to the compression of the optic chiasm by the tumor. The axons crossing in the chiasm carry information from the peripheral visual field; when pressed upon, they can disrupt signal transmission and result in visual field deficits.