Binocular counterrolling in humans during dynamic rotation.

Seven subjects 18 to 66 years old underwent 360 degrees rotation at a constant velocity of 3 degrees/sec, in 27 trials beginning randomly right ear down or left ear down. A camera on the rotating chair photographed both eyes every 10 degrees. Dual projectors measured counterrolling, the image from one projector being aligned and rotated until it was superimposed on the image from the other. Right and left eyes were measured independently. The group reached maximum counterrolling at about 70 degrees and 270 degrees in rotations to the right, with values of about -6 degrees and 4 degrees respectively. Rotations to the left reached maximum at 50 degrees and 270 degrees with about 4.5 degrees and -5.25 degrees respectively. Individual subjects showed ranges of counterrolling varying from 4.03 degrees to 17.44 degrees, mean 11.30 degrees. More counterrolling was observed when subjects were tilted to right than to left. The downward eye counterrolled more than the upward. Amount of counterrolling was inversely correlated with age.