Ocular stability in variable visual feedback conditions in the rabbit.

Summary The scarcity of eye movements in the rabbit in normal visual conditions is well known, and was confirmed by quantitative measurements. This stability is lost in darkness and replaced by irregular drift, the amplitude of which is limited by saccadic reset movements. A similar instability was observed in an optokinetic ‘open loop’ situation, created by clamping one eye (the seeing eye) and covering the other eye (moving eye). Under such conditions visual feedback is also lacking. By surrounding this preparation with a servo-driven striped drum, position-steered by the moving eye, the seeing eye was provided with information about the movements of the other eye. If the drum movement was equal to the eye movement, but opposite in direction, the moving eye was stabilized by this procedure. If the drum movement was equal to the eye movement and similar in direction, the instability was strongly enhanced (positive feedback). The difference in stability between the dark and light situations, and the open and closed loop situations, are both in agreement with earlier data on the input-output relations of the rabbit's optokinetic system.