Accommodative dynamics and attention: the influence of manipulating attentional capacity on accommodative lag and variability

Abstract

Purpose: There is evidence that attention can modulate ocular dynamics, but its effects on accommodative dynamics have yet to be fully determined. We investigated the effects of manipulating the capacity to focus on task-relevant stimuli, using two levels of dual-tasking (arithmetic task) and auditory feedback, on the accommodative dynamics at three different target distances (500, 40 and 20 cm). Methods: The magnitude and variability of the accommodative response were objectively measured in 20 healthy young adults using the Grand Seiko WAM-5500 autorefractor. In randomised order, participants fixated on a Maltese cross while 1) performing an arithmetic task with two levels of complexity (low and high mental load); 2) being provided with two levels of auditory feedback (low and high feedback); and 3) without performing any mental task or receiving feedback (control). Accommodative and pupil dynamics were monitored for 90 seconds during each of the 15 trials (5 experimental conditions x 3 target distances). Results: The lag of accommodation was sensitive to the attentional state (p = 0.001), where a lower lag of accommodation was observed for the high feedback condition compared to the control (corrected p-value = 0.009). The imposition of mental load while fixating on a distant target led to a greater accommodative response (corrected p-value = 0.010), but no effects were found for the near targets. There was a main effect of the experimental manipulation on the accommodative variability (p < 0.001), with the use of auditory feedback improving the accuracy of the accommodative system. Conclusions: Our data show that accommodative dynamics is affected by varying the capacity to focus on task-relevant stimuli, observing an improvement in accommodative stability and response with auditory feedback. These results highlight an association between attention and ocular dynamics and provide new insight into the control of accommodation.