One Eye on the Prize: The Impact of monocular vision on aiming responses

The ability to move one's hand quickly and accurately towards a target is an essential skill that underpins many activities of daily living, such as writing or threading a needle. In-lab research has previously demonstrated that the time taken to complete an aiming task is proportional to task difficulty; however, the strength of this relationship appears to reduce as the quality of visual input becomes degraded (Wu et al, 2010). There is also evidence that when compared to full vision, monocular vision leads to a general increase in movement time during aiming tasks (Sheppard et al, 2021). Despite these valuable findings, logistical challenges (e.g. recruitment from hard-to-reach populations) make in-lab testing difficult or even impossible. These potential challenges could be overcome by introducing online tests if they are sufficiently sensitive to capture visual deficits accurately. The present study aimed to test (i) whether monocular vision was associated with increased response time and (ii) the feasibility of using simple, online tasks to probe the relationship between visual and motor function. Using a computer mouse or touchpad to move to targets as quickly as possible, 65 participants (aged 18–77) completed (i) a visual search task (moving to a 34 target embedded amongst a grid of distractors) and (ii) a basic visual-motor aiming task (moving to individual targets of varying size/distance). Participants completed both tasks online, either with full vision or monocular vision. Visual search time and aiming task response time increased significantly under monocular vision (≈1.8 s and ≈40 ms, respectively). These results suggest that a simple, online aiming task can be suitable for testing the effects of a visual deficit on motor function.