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Humans use their peripheral vision during locomotion to perceive an approaching obstacle in their path, while also focusing central gaze on steps ahead of them. However, certain physiological and psychological factors may change this strategy, such as when a walker is physically fatigued. In this study, 21 healthy participants walked through a dark room while wearing eye tracking glasses before and following intense exercise. Obstacles were placed in random locations along their path and became illuminated when participants approached them. Results indicate that, when fatigued, participants had altered spatial gaze strategies, including more frequent use of central gaze to perceive obstacles and an increased gaze angular displacement. However, there were no changes in temporal gaze strategies following exercise. These findings reveal how physical fatigue alters one’s visual perception of their environment during locomotion, and may partially explain why people are at greater risk of trips and falls while fatigued.

The widespread use of virtual reality head-mounted-displays (HMDs) calls for a re-examination of the impact of prolonged exposure to fixed visual displays at close ocular proximity. The purpose of this study is to validate the Virtual Reality Symptoms Questionnaire (VRSQ), created to understand symptoms of prolonged HMDs use, and Computer Use Survey (CUS), created to assess general physical and visual discomfort symptoms. Participants (

Advancements in virtual reality (VR) technology now allow for the creation of highly immersive virtual environments and for systems to be commercially available at an affordable price. Despite increased availability, this access does not ensure that VR is appropriate for training for all motor skills. Before the implementation of VR for training sport-related skills takes place, it must first be established whether VR utilization is appropriate. To this end, it is crucial to better understand the mechanisms that drive learning in these new environments which will allow for optimization of VR to best facilitate transfer of learned skills to the real world. In this study we sought to examine how a skill acquired in VR compares to one acquired in the real world (RW), utilizing training to complete a dart-throwing task in either a virtual or real environment. We adopted a perceptual-motor approach in this study, employing measures of task performance (i.e., accuracy), as well as of perception (i.e., visual symptoms and oculomotor behavior) and motor behaviors (i.e., throwing kinematics and coordination). Critically, the VR-trained group performed significantly worse in terms of throwing accuracy compared to both the RW-trained group and their own baseline performance. In terms of perception, the VR-trained group reported greater acute visual symptoms compared to the RW-trained group, though oculomotor behaviors were largely the same across groups. In terms of motor behaviors, the VR-trained group exhibited different dart-throwing kinematics during training, but in the follow-up test adapted their throwing pattern to one similar to the RW-trained group. In total, VR training impaired real-world task performance, suggesting that virtual environments may offer different learning constraints compared to the real world. These results thus emphasize the need to better understand how some elements of virtual learning environments detract from transfer of an acquired sport skill to the real world. Additional work is warranted to further understand how perceptual-motor behaviors are acquired differently in virtual spaces.

The purpose of this study is to examine the potential relationship between tonic accommodation (TA), near work induced TA-adaptation and the steady state closed-loop accommodation response (AR). Forty-two graduate students participated in the study. Various aspects of their accommodation system were objectively measured using an open-field infrared auto-refractor (Grand Seiko WAM-5500). Tonic accommodation was assessed in a completely dark environment. The association between TA and closed-loop AR was assessed using linear regression correlations and t -test comparisons. Initial mean baseline TA was 1.84 diopter (D) (SD ± 1.29 D) with a wide distribution range (−0.43 D to 5.14 D). For monocular visual tasks, baseline TA was significantly correlated with the closed-loop AR. The slope of the best fit line indicated that closed-loop AR varied by approximately 0.3 D for every 1 D change in TA. This ratio was consistent across a variety of viewing distances and different near work tasks, including both static targets and continuous reading. Binocular reading conditions weakened the correlation between baseline TA and AR, although results remained statistically significant. The 10 min near reading task with a 3 D demand did not reveal significant near work induced TA-adaptation for either monocular or binocular conditions. Consistently, the TA-adaptation did not show any correlation with AR during reading. This study found a strong association between open-loop TA and closed-loop AR across a variety of viewing distances and different near work tasks. Difference between the correlations under monocular and binocular reading condition suggests a potential role for vergence compensation during binocular closed-loop AR.

Grapheme-color synesthetes experience a sense of color when viewing graphemes (e.g., digits and letters). Traditionally, these synesthetic perceptions are considered to be unidirectional, where viewing a grapheme elicits a nonveridical sensation of color, but viewing a color does not induce a reciprocal sense of a grapheme. A growing body of research has emerged that suggests the potential for bidirectional percepts, wherein color facilitates additional grapheme perception. We present here a novel paradigm in which we presented two sets of pure color patches, based on synesthete’s reported colors, side-by-side and asked participants to indicate the color patch with the greater affiliated magnitude. Results indicated that the odds of answering correctly on trials were significantly greater for synesthetes (80.2% accuracy) than nonsynesthetes (52.1% accuracy). These results are aligned with other reports that support the notion of inducing a sense of magnitude from color in synesthetes. These findings challenge the traditional model of synesthesia as a unidirectional phenomenon and have implications of the neuronal communications that underlie perception in general.

Purpose Several surveys exist to determine the severity and frequency of chronic symptoms related to visual discomfort. To our knowledge, there are no studies that investigate the potential of chronic visual discomfort ratings to predict acute discomfort symptoms that are experienced after tests of accommodation and vergence. We examined the ability of two measures of chronic visual discomfort symptoms to predict acute symptoms experienced. Methods The Conlon et al. and the convergence insufficiency symptom surveys were administered to 40 participants to assess chronic visual discomfort symptoms. Two measures were used to assess acute symptoms. The first consisted of four Likert-scaled questions relating to comfort level during last test, visual distortions or movement, discomfort caused by overhead lights, and presence of headache symptoms. These questions were asked before and after binocular examination, and the scores were used to generate a postexamination symptom score. The second measure of acute symptoms consisted of participants rating their general discomfort on a four-point Likert scale after each binocular test, and the ratings were summed to produce a General Symptom Score. Participants were then categorized into a high or low Post-exam symptom group and General symptom group. Data were analyzed with a binary logistic regression to determine whether the chronic surveys could predict acute symptom group classification. Results Approximately 75% of predictions were accurate for either chronic symptom survey. Headache, soreness, and eye-related questions were more reliable predictors of symptom acute outcome. Conclusions These data suggest that the Conlon and Convergence Insufficiency Symptom Survey (CISS) surveys are good predictors of acute symptoms induced during a binocular examination and validate the use of chronic symptom surveys as screening tools for symptomatic binocular dysfunction. Further investigation is required to determine predictability of accommodative or vergence performance.

Purpose Asthenopia is a common problem associated with near work and reports suggest that colored lenses or overlays may be applied to reduce symptoms. In this study, we examine the relationship between eyestrain, color preferences, and function of the accommodation and vergence system. Specifically, we examine whether symptomatic observers select colors that reduce accommodative demand based on longitudinal chromatic aberration (LCA). Methods Forty-seven undergraduate students participated in this study. Visual discomfort symptoms were assessed using the Conlon survey. A Mark 2 Intuitive Colorimeter was used to obtain optimal colored light preferences. LCA was modeled using the Chromatic Eye and spectral power density data. A comprehensive evaluation of accommodation and vergence was performed following standard procedures. Results A significant negative correlation (r = -0.51) was found between eyestrain symptoms and the International Commission on Illumination (CIE) v' axis of colors preferences. Additionally, a significant negative correlation (r = -0.31) was found between eyestrain symptoms and LCA accommodation. Two thirds of the participants in the high discomfort group chose colors that decreased accommodative demand. Accommodative amplitude and vergence facility also correlated with LCA, accounting for 25% of the variance. Conclusions The color preferences of individuals are systematically influenced by the functioning of their accommodation and vergence systems with increased symptomatology resulting in color selections that reduce LCA accommodative stimulus demand.

How well can observers selectively attend only to dots that are lighter or darker than the background when all dot intensities are present? Observers estimated centroids of briefly flashed, sparse clouds of 8 or 16 dots, ranging in intensity from dark black to bright white on a gray background. Attention instructions were to equally weight: (i) dots brighter than the background, assigning zero weight to others; (ii) dots darker than the background, assigning zero weight to others; (iii) all dots. For each observer, a quantitative estimate of the operational attention filter (the weight exerted in the centroid estimates as a function of dot intensity) was derived for each attention instruction in each dot condition. Attended dots typically have 4× the weights of unattended dots. Whereas observers performed remarkably well in estimating centroids and achieving the three required attention filters, they achieved higher accuracy when equally weighing all dots than when selectively attending to dots of only one contrast polarity. Although their attention filters are similar, individual observers use significantly different parameters in their centroid computations. The complete model of performance enables perceptual measurements of observers' attention filters for shades of gray that are as accurate as physical measurements of color filters.