On the effective number of tracked trajectories in amblyopic human vision.

We estimated the effective number of trajectories that amblyopic observers could track with their amblyopic eyes and their non-amblyopic eyes using stimuli and methods described in S. P. Tripathy, S. Narasimhan, and B. T. Barrett (2007). The stimuli consisted of dots moving along straight-line trajectories. In Experiment 1, one of the T trajectories (the target) deviated clockwise or counterclockwise by +/-19 degrees , +/-38 degrees , or +/-76 degrees , halfway through the trajectory. In Experiment 2, D of the T trajectories deviated, all in the same direction and with the same magnitude of direction change. In both experiments, we varied T and the angle of deviation. In Experiment 2, we also varied D. Amblyopic observers reported the direction of deviation of the target trajectories and, for each eye, the effective number of tracked trajectories was estimated. This number increased systematically with increasing magnitude of deviation of the targets. On average, the effective numbers of tracked trajectories were approximately 15% smaller for the amblyopic eyes for each of the three magnitudes of deviation. A comparison with data previously published for normal eyes failed to reveal any deficit in the effective number of trajectories tracked by the non-amblyopic eyes of amblyopic observers for the current task.