Assessment of retinal image displacement during head movement using an afterimage method.

An afterimage method has been used to measure retinal image displacement during binocular fixation with active head rotation about a vertical axis. The results confirm previously published reports that fixation accuracy in the horizontal direction deteriorates as a result of a head rotation. However, both retinal image displacements and fixation disparities were found to remain much smaller (by a factor of 3 and 8 respectively) than the values previously reported in the literature for similar head rotations (peak-to-peak amplitude: 20 degrees, frequency: 0.66 Hz). Moreover, our results show that fixation accuracy fell not only in the horizontal direction, but also in the vertical direction by about the same factor. It is concluded that eye-movement compensation of active head rotation may be much better than previously reported in the literature, and good enough to prevent deterioration of vision.