A type of visual field loss in which vision is lost in the outer (temporal) half of the visual field of both eyes. The most common cause of baytemporal hemianopia is a pituitary tumor (such as adenoma), but it can also be caused by trauma, stroke, or other lesions of the optic cross. People with baytemporal hemianopia may have difficulty seeing objects on the outside of each eye and may have trouble doing activities such as driving a car or moving around crowded places. Treatment depends on the underlying cause and may include surgical removal of the tumor, radiation therapy, or other medical interventions.