The total expanse of space (both central and peripheral), where an object is visible at a given instant during stable gaze fixation in one direction. A typical vision field should measure 90 degrees temporally to central fixation, 60 degrees inferiorly, and 50 degrees superiorly and nasally. Diseases that can affect the visual field include stroke, hypertension, glaucoma, multiple sclerosis, overactive thyroid gland, and diabetes.