Wang Ailing¹ (), Gao Mingjie¹, Zhu Weina², Jan Drewes¹; ¹Institute of Brain and Psychological Sciences, Sichuan Normal University, Chengdu, China, ²School of Information Science, Yunnan University, Kunming, China

Saccades, the fastest-moving eye movements, may not stop exactly at the position of the intended gaze point, but continue to oscillate for a short period. This instability is known as post-saccadic overshoot (PSO). Here we investigate whether different lateral/horizontal saccade directions (adduction [to the nose] or abduction [from the nose]) would have an effect on saccade parameters, and if so, how the directions would affect PSO and whether the aging ocular system follows the same pattern. There are three parts of the study, (i) the effect of direction on saccade movement, (ii) the effect of different directions of saccade movement on PSO, and (iii) the difference in PSO between a younger group (under 26 years) and a senior group (over 55 years). To generate saccades, we required participants to repeatedly follow a jumping target, and recorded with a video-based eye tracker. Our main findings are: (1) Adduction saccades have a significantly higher acceleration in the young participants than abduction saccades, but not in senior participants. (2) In the young participants, adduction saccades have higher acceleration compared to abduction saccades and consequently triggered higher PSO amplitude, while PSO amplitudes in senior participants did not show differences. (3) Abduction saccades peak velocity in young participants was significantly higher than adduction peak velocity, but not in senior participants. (4) Adduction deceleration is not significantly different from abduction in both young and senior participants. (5) Senior participants make fewer long-distance saccades (but more short saccades) in both directions. Our results show that saccade direction has a significant effect on the saccadic movement profile. Saccadic acceleration can help us predict PSO amplitude, yet not in aging eyes, as there is no difference in the senior participant group between adduction and abduction.

Acknowledgements: Supported by the National Natural Science Foundation of China (61263042, 61563056)