Study of visual acutiy during the ocular pursuit of moving test objects. II. Effects of direction of movement, relative movement, and illumination.

It was demonstrated that the manner in which visual acuity deteriorates as the angular velocity of the test object increases is similar regardless of whether the motion is produced by moving the target vertically, horizontally, or by rotating the observer in a horizontal plane. It was shown also that the semiempirical equation Y=a+bx3 describes satisfactorily these three types of movement. It was pointed out that individuals having a low acuity threshold in the vertical plane of movement will be likely also to have a low threshold in the horizontal plane. It was shown that although 5 to 10 footcandles may be sufficient illumination when the test object is stationary, visual acuity is substantially benefitted by increases up to 125 footcandles when the observer is rotated. This corroborates earlier findings reported by Ludvigh.