Brief intermittent light stimulation disrupts saccadic oculomotor control

Bright-light distractions and visual performance

Visual distractions pose a significant risk to transportation safety, with laser attacks against aircraft pilots being a common example. This study used a research-grade High Dynamic Range (HDR) display to produce bright-light distractions for 12 volunteer participants performing a combined visual task across central and peripheral visual fields. The visual scene had an average luminance of 10 cd∙m^-2 with targets of approximately 0.5° angular size, while the distractions had a maximum luminance of 9,000 cd∙m^-2 and were 3.6° in size. The dependent variables were the mean fixation duration during task execution (representative of information processing time), and the critical stimulus duration required to support a target level of performance (representative of task efficiency). The experiment found a statistically significant increase in mean fixation duration, rising from 192 ms without distractions to 205 ms with bright-light distractions (p = 0.023). This indicates a decrease in visibility of the low contrast targets or an increase in cognitive workload that required greater processing time for each fixation in the presence of the bright-light distractions. Mean critical stimulus duration was not significantly affected by the distraction conditions used in this study. Future experiments are suggested to replicate driving and/or piloting tasks and employ bright-light distractions based on real-world data, and we advocate the use of eye-tracking metrics as sensitive measures of changes in performance.

Effects of visual distractors on vergence eye movements

Visual attention is an important aspect of everyday life, which can be incorporated in the assessment of many diagnoses. Another important characteristic of visual attention is that it can be improved via therapeutic interventions. Fifteen subjects with normal binocular vision were presented with visual distractor stimuli at various spatial locations while initiating disparity vergence eye movements (inward or outward rotation of eyes) within a haploscope system. First, a stationary distractor stimulus was presented in either the far, middle, or near visual spaces while the subjects were instructed to follow a target stimulus that was either stationary, converging (moving toward subject), or diverging (moving away from subject). For the second experiment, a dynamic distractor stimulus within the far, middle, or near visual space that was converging or diverging was presented while the target stimulus was also converging or diverging. The subjects were instructed to visually follow the target stimulus and ignore the distractor stimulus. The vergence responses had a final vergence angle between the target and distractor stimuli which has been termed a center of gravity (CoG) effect. Statistically significant differences were observed between the convergence peak velocities (p < 0.001) and response amplitudes (p < 0.001) comparing responses without distractors to responses with the presence of a vergence distractor. The results support that vergence eye movements are influenced by visual distractors, which is similar to how distractors influence saccadic eye movements. The influence of visual distractors within vergence eye movements may be useful to assess binocular dysfunction and visual distraction which are common post brain injury.