The effect of moving and static trans-scleral illumination of visual afterimages

The inside of the eye was illuminated by shining a small light through the upper eyelid and the sclera. After viewing a bright light flash, Ss closed their eyes and reported the duration of the afterimage under the following conditions: the light on and moving across the S’s eyelid (moving trans-scleral illumination), the light on but stationary (static trans-scleral illumination), and two corresponding control conditions in which the light was turned off (darkness). Results indicate that when the trans-scleral light is moving, afterimages are seen clearly for periods of approximately the same duration as those seen in complete darkness. However, when the trans-scleral illumination is stationary, the duration of the afterimages is significantly reduced. These results are compatible with other afterimage data that suggest that changes within the field after initial stimulation are needed to prolong afterimages.