What Is Hemianopia (Hemianopsia)?

4. Causes of bi-temporal or heteronymous hemianopia

A chiasmal lesion pressing on the nasal fibers from each eye will more likely result in a bi-temporal hemianopia. Bi-temporal hemianopia suggests, for example, a compression of the optic chiasm produced by a pituitary gland tumor developing along the midline. This type of tumor is often slow-growing. Since the pituitary gland is responsible for regulation of the body's hormones, the visual field defect will be associated with symptoms of hormonal imbalance. The disease process may impair hormone secretion. And possibly lead to a lack of one or several hormones produced by the gland. Alternatively, the tumor can itself produce hormones in excess, leading to high levels of hormones producing a specific clinical syndrome.