2018 Volume 64 Issue Suppl.1 Pages 69-70
Purpose: Eye movements are important factors for dynamic visual acuity (DVA) that refers to the ability to perceive fine details of a moving object. When tracking a moving visual stimulus, we often combine smooth eye movements with catch-up saccades. The velocity of saccade eye movements (up to 500-600 deg/s) is much faster than smooth pursuit (usually less than 50 deg/s). Tracking ability using these two kinds of eye movements is thought to play a critical role in DVA and better DVA is associated with an ability of catch-up saccades. However, it is still uncertain whether eye movements and speed perception have directional asymmetry when tracking a moving object. The purpose of this study was to quantitatively clarify the effects of visual target directions on training of DVA and concomitant eye movements. Therefore, we repetitively measured the eye movements during DVA training and attempted to determine the effects of visual target directions on saccade eye movements.
Methods: DVA was evaluated by a moving visual target (Landolt ring) that was projected on the front screen (HI-10; Kowa, Japan). Eye movements were detected using a video based eye tracking system (Eye Link1000; SR research, Canada). We have performed measuring DVA in eight subjects (mean age; 18.7±1.0, age range; 18 to 21 years old) and analyzed saccades eye movements quantitatively using custom analytical software (Matlab; Mathworks Inc., USA). Subjects were seated in front of a screen and put their jaw on a chin supporter of our device to stabilize the head. The subjects were asked to follow the Landolt ring moving across in front of their visual field and judge the direction of the slit. We defined a total of forty trials as one set of training and subjects were given three sets of training every other day. Thus, each subject performed 120 trials in total. We analyzed saccade latency (msec), peak velocity (deg/sec), error (deg) and a correct response rate (%). The Landolt ring moved either from right to left or left to right with constant speed of 300 deg/s.
A total of eight measurements were performed for each subject before and after vision training. We examined whether the visual target directions influence training effect of DVA and eye movements such as saccade latency, peak velocity, error.
Results: Our results demonstrated that saccade latency and error showed significant decreases and the correct response rate increased after training for eight subjects. In contrast, saccade peak velocity showed different results among subjects. There was no tendency in velocity after training. The ability of DVA did not show a statistical difference between the left-right direction and the right-left direction before training. Training effect of latency and error also showed no difference between the directions.
Conclusion: Our study provided several lines of evidence showing that saccade eye movements, such as latency, error and peak velocity changed after vision training. And the effects of vision training on DVA and eye movements were not differ in terms of the target directions. Our results suggest that DVA and eye movements may not be biased towards the target direction.
