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Purpose: Asthenopia is related to near vision activities or visual tasks that dissociate accommodation from vergence. Since the results of previous studies using objective measures to diagnose asthenopia are inconsistent, this study compared optometric tests and objective metrics of accommodation in non‐asthenopic and asthenopic young adults before and after a visual fatigue task. Methods: The accommodative response was recorded objectively for 6 min at a 3.33 D accommodative demand using an autorefractor, before and after a 5‐min non‐congruent visual task. Accommodation was disassociated from vergence with a ±2.00 D accommodative flipper while reading at the same distance. Optometric tests and subjective evaluations of asthenopia were performed before and after the task. Twenty‐six non‐presbyopic adults (23.15 ± 2.56 years) were included and identified as asthenopic (n = 14) or non‐asthenopic (n = 12) based on their score on the Computer Vision Syndrome Questionnaire. Results: A mixed ANOVA found no significant difference between the groups for objective (accommodative response) or subjective metrics (feeling of fatigue, optometric tests), although all participants reported greater visual fatigue after the task. A significant effect of time (before and after the non‐congruent task) was identified for the overall sample for mean accommodative lag (+0.10 D, p = 0.01), subjective visual fatigue (+1.18, p < 0.01), negative relative accommodation (−0.20 D, p = 0.02) and near negative fusional reserve (blur: +2.46Δ, p < 0.01; break: +1.89Δ, p < 0.01; recovery: +3.34Δ, p = 0.02). Conclusions: The task‐induced asthenopia, measured both objectively and subjectively, was accompanied by a change in accommodative lag, greater visual fatigue and a decrease in negative relative accommodation. Conversely, near negative fusional reserves seem to adapt to the task. No significant differences were found between the two groups with respect to accommodative metrics (objective) or subjective and optometric tests. [ABSTRACT FROM AUTHOR]

INTRODUCTION Stereoscopic displays are becoming an increasingly common feature of human-machine interfaces, and display technology has improved dramatically over the last few years (Patterson, Moe, & Hewitt, 1992; Sollenberger & […], Factors limiting binocular fusion were studied using 2-dimensional difference of Gaussian (2D-DOG) stimuli. The proportion of fused stimuli and observer's response time were determined for stimuli that varied in spatial frequency composition between 0.22 and 4.8 cycles per degree. At small disparities, mean fusion response times were short and relatively stable but increased rapidly once the disparity reached a certain critical value. This 2-phase function implies the existence of 2 separate fusional mechanisms: a rapid neurally based fusional process, which operates at small disparities, and a second mechanism involving reflexive vergence movements operating at disparities 2 to 3 times larger. Both mechanisms are highly influenced by spatial frequency, being 4 to 5 times more effective at low spatial frequencies. Additional experiments demonstrated that with compound stimuli, the fusion limit is not determined by the highest spatial frequency components (as had been reported previously) but, rather, can take advantage of the additional fusional range associated with low spatial frequencies. Such cooperation may be obvious only in the case of 2-dimensional stimuli.

In monocular see-through augmented reality systems, each eye is stimulated differently by a monocular image that is superimposed on the binocular background. This can impair binocular fusion, due to interocular conflict. As a function of visual characteristics, the latter can have a greater or lesser impact on user comfort and performance. This study tested several visual characteristics of a binocular background and a monocular element during an exposure that reproduced the interocular conflict induced by a monocular see-through near-eye display. The aim was to identify which factors impact the user's performance. Performance was measured as target tracking and event detection, identification, fixation time, and latency. Our results demonstrate that performance is a function of the binocular background. Furthermore, exogenous attentional stimulation, in the form of a pulse with different levels of contrast applied to the monocular display, appears to preserve performance in most background conditions. [ABSTRACT FROM AUTHOR]

We present one method for detecting defects on an inclined textured plane. This method uses a combination of a shape from texture (SFT) method with the Delaunay triangulation technique. The SFT method provides the theoretical equation of the plane orientation in two steps. First, a wavelet decomposition allows us to build an image of the inverse of the local frequency, that is the scale, that we call the local scales map. Then we perform an interpolation of this map using the equation of the theoretical variation of the scales. With the interpolation parameters it is possible to extract the texels by the use of an adaptive thresholding for each pixel of this map. Then we compute the centers of each texel in order to match a mesh on it after processing a Delaunay triangulation. When there is a defect, the regularity of the triangulation is disturbed, so one hole appears in the mesh.

Imaging displays have lacked several characteristics of direct vision such as true stereopsis, and this may in part account for some loss in visual performance when compared with direct vision. One such decrement in performance is in judgments of distance. An experiment is reported in which judgments of distance of targets were obtained from videotaped images of targets in a natural outdoor scene. Presentations were made under 3 conditions: stereo with near or far zero disparities and binocular nonstereo ("biocular") viewing. Underconstancy was found to be less for stereo presentation, but only when the point of zero disparity was in the plane of presentation of the virtual image. Some implications for the design of cockpit imaging displays are discussed. [ABSTRACT FROM AUTHOR]

When looking at objects at various distances in the physical space, the accommodation and vergence systems adjust their parameters to provide a single and clear vision of the world. Subtended muscle activity provides oculomotor cues that can contribute to the perception of depth and distance. While several studies have outlined the role of vergence in distance perception, little is known about the contribution of its concommitant accommodation component. It is possible to unravel the role of each of these physiological systems by placing observers in a situation where there is a conflict between accommodation and vergence distances. We thus sought to determine the contribution of each response system to perceived depth by simultaneously measuring vergence and accommodation while participants judged the depth of 3D stimuli. The distance conflict decreased depth constancy for stimulus displayed with negative disparity steps (divergence). Although vergence was unaffected by the stimulus distance, accommodation responses were significantly reduced when the stimulus was displayed with negative disparities. Our results show that biases in perceived depth follow undershoots in the disparity-driven accommodation response. These findings suggest that accommodation responses (i.e., from oculomotor information) can contribute to perceived depth.

Vertical binocular disparity is a source of distance information allowing the portrayal of the layout and 3D metrics of the visual space. The role of vertical disparity in the perception of depth, size, curvature, or slant of surfaces was revealed in several previous studies using cue conflict paradigms. In this study, we varied the configuration of stereo-cameras to investigate how changes in the horizontal and vertical disparity fields, conflicting with the vergence cue, affect perceived distance and depth. In four experiments, observers judged the distance of a cylinder displayed in front of a large fronto-parallel surface. Experiment 1 revealed that the presence of a background surface decreases the uncertainty in judgments of distance, suggesting that observers use the relative horizontal disparity between the target and the background as a cue to distance. Two other experiments showed that manipulating the pattern of vertical disparity affected both distance and depth perception. When vertical disparity specified a nearer distance than vergence (convergent cameras), perceived distance and depth were underestimated as compared with the condition where vertical disparity was congruent with vergence cues (parallel cameras). When vertical disparity specified a further distance than vergence, namely an infinite distance, distance and depth were overestimated. The removal of the vertical distortion lessened the effect on perceived distance. Overall, the results suggest that the vertical disparity introduced by the specific camera configuration is mainly responsible for the effect. These findings outline the role of vertical disparity in distance and depth perception and support the use of parallel cameras for designing stereograms.

When stimuli are repeated in a rapid serial visual presentation (RSVP), observers sometimes fail to report the second occurrence of a target. This phenomenon is referred to as "repetition blindness" (RB). We report an RSVP experiment with photographs in which we manipulated object viewpoints between the first and second occurrences of a target (0°, 45°, or 90° changes), and spatial frequency (SF) content. Natural images were spatially filtered to produce low, medium, or high SF stimuli. RB was observed for all filtering conditions. Surprisingly, for full-spectrum (FS) images, RB increased significantly as the viewpoint reached 90°. For filtered images, a similar pattern of results was found for all conditions except for medium SF stimuli. These findings suggest that object recognition in RSVP are subtended by viewpoint-specific representations for all spatial frequencies except medium ones.