A black tangent screen intended for assessing the extent of the patient's peripheral visual field by mapping the visual response to a test object moved from the periphery towards the centre of the screen. It typically consists of a series of concentric circles and a number of radii equally spaced around the circumference and is used in conjunction with a hand-held wand with a distal white spot or illuminated tip and black marking pins. The results are recorded manually on a corresponding chart. Also known as a Bjerrum screen.