Pituitary tumors, called adinomas are not rare. These can lower LH/FSH thus reducing T, or increasing prolactin, which also lowers LH/FSH as a negative feedback signal on the HPTA. The adinoma can press on one or both optic nerves, which pass right by the pituitary, which can reduce peripheral vision or create other visual field disturbances [not refractive errors]. Any such changes should also be brought to the attention of an eye specialist, in case there is something going on wrong with the eye.
Some vision problems can be a symptom of hypogonadism.