Abstract
Continuous target-tracking tasks allow experimenters to collect perceptual data quickly and efficiently, thereby reducing the amount of time needed for an observer to complete a particular task. This has the potential to be particularly helpful in clinical settings, where the time clinicians have with patients for assessment and/or research can be extremely limited. To explore the potential clinical utility of continuous target-tracking tasks, we designed three tasks aimed specifically at assessing the severity of optic neuritis (ON), a condition caused by inflammation of the optic nerve. Adult-onset ON, a common initial sign of multiple sclerosis (MS), is typically unilateral, and symptoms can include decreased visual acuity and impaired perception of motion, color, and depth. We designed (1) a basic tracking task meant to assess visual acuity and motion perception; (2) an isoluminant tracking task meant to additionally assess color perception; and (3) a task meant to test whether observers experience the Pulfrich phenomenon, an indication of impaired depth perception. As an initial step in determining whether these tasks could help evaluate symptom severity, we had healthy control subjects complete these tasks with varying amounts of monocular visual impairment, which we simulated by reducing the level of light reaching an eye via a polarizing filter, the strength of which depends on its relative angle. Results showed that our manipulation could induce the Pulfrich phenomenon and that the strength of the effect depended on the strength of the filter. We found additional relationships between filter strength and the spatiotemporal accuracy of tracking performance (e.g., the lag of the peak cross-correlation between the stimulus and response velocities), suggesting that continuous target-tracking has the potential to be a useful clinical tool. Data from clinical populations will be needed to confirm that possibility and to determine how tracking performance relates to established clinical metrics.