The main reason for the symptoms of pituitary tumor affecting vision is that the pituitary tumor is very close to the optic nerve, and when it grows to a certain extent, it can compress the optic nerve and cause corresponding visual dysfunction. The typical manifestation may be bilateral temporal hemianopsia, and the typical visual field defect is firstly the involvement of the superior temporal quadrant, and then the involvement of the inferior temporal, inferior nasal and superior nasal quadrants. Visual impairment is usually caused by advanced optic nerve atrophy, but some patients may also have visual field defects even when the optic nerve is not compressed, which is mainly due to blood stealing from the blood vessels shared by the optic nerve and the pituitary tumor, which interferes with the normal blood supply of the optic nerve.