Evaluating lawful relationships in saccadic eye movements with simulated vision impairment: A proof-of-concept study.

The aim of this study was to examine the degree to which known lawful relationships in saccadic eye movements hold when visual acuity is artificially degraded. If lawful relationships still hold, then violations during the vision assessment could indicate that individuals are not performing with their maximum effort in an effort to exaggerate their impairment. Twelve healthy participants performed saccades between targets of different sizes and at different separations from each other. Each participant completed the task with habitual vision and with three levels of simulated impairment. Saccade duration and fixation dispersion both increased with target separation, irrespective of the simulated visual impairment (R values of 0.78 for duration and 0.27 for dispersion). Some eye movement measures retained lawful relationships with task constraints even when visual input was degraded. Although the present study does not assess the ability of these measures to detect intentional misrepresentation, the dependency of saccade duration and fixation dispersion on target separation under simulated vision impairment identifies them as candidate variables for future work aimed at improving confidence in vision assessments. Future work should examine whether saccade duration and fixation dispersion show the same lawful relationship in actual vision impairment.