26. Red Desaturation
Visual Fields. Test visual fields for each eye by asking the patient to fixate straight ahead and to report when a finger can be seen moving in each quadrant. Alternatively, ask the patient to report how many fingers are being shown in each quadrant. More precise mapping of visual fields can be done in the laboratory for patients who will be followed over time (see KCC 11.2). In comatose or uncooperative patients (discussed later in this chapter), visual fields can be tested roughly using blink-to-threat.
Visual Extinction. Test for visual extinction on double simultaneous stimulation by asking the patients how many fingers they see when fingers are presented to both sides at the same time. In visual extinction, a form of hemineglect, patients do not report seeing the fingers on the affected (usually left) side of the visual field, although they can see fingers when they are presented to that side alone.