Showing papers on "Foveal published in 2017"

Latency Requirements for Foveated Rendering in Virtual Reality

Abstract: Foveated rendering is a performance optimization based on the well-known degradation of peripheral visual acuity. It reduces computational costs by showing a high-quality image in the user’s central (foveal) vision and a lower quality image in the periphery. Foveated rendering is a promising optimization for Virtual Reality (VR) graphics, and generally requires accurate and low-latency eye tracking to ensure correctness even when a user makes large, fast eye movements such as saccades. However, due to the phenomenon of saccadic omission, it is possible that these requirements may be relaxed.In this article, we explore the effect of latency for foveated rendering in VR applications. We evaluated the detectability of visual artifacts for three techniques capable of generating foveated images and for three different radii of the high-quality foveal region. Our results show that larger foveal regions allow for more aggressive foveation, but this effect is more pronounced for temporally stable foveation techniques. Added eye tracking latency of 80--150ms causes a significant reduction in acceptable amount of foveation, but a similar decrease in acceptable foveation was not found for shorter eye-tracking latencies of 20--40ms, suggesting that a total system latency of 50--70ms could be tolerated.

Variations in crowding, saccadic precision, and spatial localization reveal the shared topology of spatial vision

Abstract: Visual sensitivity varies across the visual field in several characteristic ways. For example, sensitivity declines sharply in peripheral (vs. foveal) vision and is typically worse in the upper (vs. lower) visual field. These variations can affect processes ranging from acuity and crowding (the deleterious effect of clutter on object recognition) to the precision of saccadic eye movements. Here we examine whether these variations can be attributed to a common source within the visual system. We first compared the size of crowding zones with the precision of saccades using an oriented clock target and two adjacent flanker elements. We report that both saccade precision and crowded-target reports vary idiosyncratically across the visual field with a strong correlation across tasks for all participants. Nevertheless, both group-level and trial-by-trial analyses reveal dissociations that exclude a common representation for the two processes. We therefore compared crowding with two measures of spatial localization: Landolt-C gap resolution and three-dot bisection. Here we observe similar idiosyncratic variations with strong interparticipant correlations across tasks despite considerably finer precision. Hierarchical regression analyses further show that variations in spatial precision account for much of the variation in crowding, including the correlation between crowding and saccades. Altogether, we demonstrate that crowding, spatial localization, and saccadic precision show clear dissociations, indicative of independent spatial representations, whilst nonetheless sharing idiosyncratic variations in spatial topology. We propose that these topological idiosyncrasies are established early in the visual system and inherited throughout later stages to affect a range of higher-level representations.

Saccade landing position prediction for gaze-contingent rendering

Abstract: Gaze-contingent rendering shows promise in improving perceived quality by providing a better match between image quality and the human visual system requirements. For example, information about fixation allows rendering quality to be reduced in peripheral vision, and the additional resources can be used to improve the quality in the foveal region. Gaze-contingent rendering can also be used to compensate for certain limitations of display devices, such as reduced dynamic range or lack of accommodation cues. Despite this potential and the recent drop in the prices of eye trackers, the adoption of such solutions is hampered by system latency which leads to a mismatch between image quality and the actual gaze location. This is especially apparent during fast saccadic movements when the information about gaze location is significantly delayed, and the quality mismatch can be noticed. To address this problem, we suggest a new way of updating images in gaze-contingent rendering during saccades. Instead of rendering according to the current gaze position, our technique predicts where the saccade is likely to end and provides an image for the new fixation location as soon as the prediction is available. While the quality mismatch during the saccade remains unnoticed due to saccadic suppression, a correct image for the new fixation is provided before the fixation is established. This paper describes the derivation of a model for predicting saccade landing positions and demonstrates how it can be used in the context of gaze-contingent rendering to reduce the influence of system latency on the perceived quality. The technique is validated in a series of experiments for various combinations of display frame rate and eye-tracker sampling rate.

Evidence for simultaneous syntactic processing of multiple words during reading.

Abstract: A hotly debated issue in reading research concerns the extent to which readers process parafoveal words, and how parafoveal information might influence foveal word recognition. We investigated syntactic word processing both in sentence reading and in reading isolated foveal words when these were flanked by parafoveal words. In Experiment 1 we found a syntactic parafoveal preview benefit in sentence reading, meaning that fixation durations on target words were decreased when there was a syntactically congruent preview word at the target location (n) during the fixation on the pre-target (n-1). In Experiment 2 we used a flanker paradigm in which participants had to classify foveal target words as either noun or verb, when those targets were flanked by syntactically congruent or incongruent words (stimulus on-time 170 ms). Lower response times and error rates in the congruent condition suggested that higher-order (syntactic) information can be integrated across foveal and parafoveal words. Although higher-order parafoveal-on-foveal effects have been elusive in sentence reading, results from our flanker paradigm show that the reading system can extract higher-order information from multiple words in a single glance. We propose a model of reading to account for the present findings.

The quantitative measurements of foveal avascular zone using optical coherence tomography angiography in normal volunteers.

Abstract: Purpose To provide normative data of foveal avascular zone (FAZ) and thickness. Methods In this cross-sectional study both eyes of each normal subject were scanned with optical coherence tomography angiography (OCTA) for foveal superficial and deep avascular zone (FAZ) and central foveal thickness (CFT) and parafoveal thickness (PFT). Results Out of a total of 224 eyes of 112 volunteers with a mean age of 37.03 (12–67) years, the mean superficial FAZ area was 0.27 mm2, and deep FAZ area was 0.35 mm2 (P Conclusion The gender and CFT influence the size of normal superficial and deep FAZ of capillary network.

Selective enhancement of orientation tuning before saccades.

Abstract: Saccadic eye movements cause a rapid sweep of the visual image across the retina and bring the saccade's target into high-acuity foveal vision. Even before saccade onset, visual processing is selectively prioritized at the saccade target. To determine how this presaccadic attention shift exerts its influence on visual selection, we compare the dynamics of perceptual tuning curves before movement onset at the saccade target and in the opposite hemifield. Participants monitored a 30-Hz sequence of randomly oriented gratings for a target orientation. Combining a reverse correlation technique previously used to study orientation tuning in neurons and general additive mixed modeling, we found that perceptual reports were tuned to the target orientation. The gain of orientation tuning increased markedly within the last 100 ms before saccade onset. In addition, we observed finer orientation tuning right before saccade onset. This increase in gain and tuning occurred at the saccade target location and was not observed at the incongruent location in the opposite hemifield. The present findings suggest, therefore, that presaccadic attention exerts its influence on vision in a spatially and feature-selective manner, enhancing performance and sharpening feature tuning at the future gaze location before the eyes start moving.

Diagnosing the Periphery: Using the Rey-Osterrieth Complex Figure Drawing Test to Characterize Peripheral Visual Function

Abstract: Peripheral vision is strongly limited by crowding, the deleterious influence of neighboring stimuli on target perception Many quantitative aspects of this phenomenon have been characterized, but the specific nature of the perceptual degradation remains elusive We utilized a drawing technique to probe the phenomenology of peripheral vision, using the Rey-Osterrieth Complex Figure, a standard neuropsychological clinical instrument The figure was presented at 12° or 6° in the right visual field, with eye tracking to ensure that the figure was only presented when observers maintained stable fixation Participants were asked to draw the figure with free viewing, capturing its peripheral appearance A foveal condition was used to measure copying performance in direct view To assess the drawings, two raters used standard scoring systems that evaluated feature positions, spatial distortions, and omission errors Feature scores tended to decrease with increasing eccentricity, both within and between conditions, reflecting reduced resolution and increased crowding in peripheral vision Based on evaluation of the drawings, we also identified new error classes unique to peripheral presentation, including number errors for adjacent similar features and distinctive spatial distortions The multifaceted nature of the Rey-Osterrieth Complex Figure-containing configural elements, detached compound features, and texture-like components-coupled with the flexibility of the free-response drawing paradigm and the availability of standardized scoring systems, provides a promising method to probe peripheral perception and crowding

Optical coherence tomography angiography of foveal hypoplasia.

Abstract: Aims To discuss foveal development in the context of detailed retinal vasculature imaging in foveal hypoplasia using optical coherence tomography angiography. Methods In this case series, the optical coherence tomography angiography results of four patients with idiopathic foveal hypoplasia and two patients with foveal hypoplasia secondary to oculocutaneous albinism are presented. Results Cases with intact visual acuity demonstrated lower grades of foveal hypoplasia on optical coherence tomography, while those with poor vision demonstrated high grades of foveal hypoplasia. The superficial retinal capillary plexus was intact in the foveal area in all cases, with no demonstrable foveal avascular zone. The deep retinal capillary plexus was absent to variable degrees in most cases, but was most persistent in those cases with reduced vision. Conclusions The superficial retinal capillary plexus is present in cases with foveal hypoplasia, while the deep retinal capillary plexus is absent to varying degrees. Our findings support the hypothesis that an intact foveal avascular zone of the deep capillary plexus allows for outer retinal photoreceptor specialisation to occur unimpeded, resulting in preserved visual acuity, while this process may be inhibited by an absent deep capillary foveal avascular zone with resultant poor vision.

Integration of parafoveal orthographic information during foveal word reading: beyond the sub-lexical level?

Abstract: Prior research has shown that processing of a given target word is facilitated by the simultaneous presentation of orthographically related stimuli in the parafovea. Here we investigate the nature ...

Perceptual learning improves contrast sensitivity, visual acuity, and foveal crowding in amblyopia

Abstract: BACKGROUND: Amblyopic observers present abnormal spatial interactions between a low-contrast sinusoidal target and high-contrast collinear flankers. It has been demonstrated that perceptual learning (PL) can modulate these low-level lateral interactions, resulting in improved visual acuity and contrast sensitivity. OBJECTIVE: We measured the extent and duration of generalization effects to various spatial tasks (i.e., visual acuity, Vernier acuity, and foveal crowding) through PL on the target's contrast detection. METHODS: Amblyopic observers were trained on a contrast-detection task for a central target (i.e., a Gabor patch) flanked above and below by two high-contrast Gabor patches. The pre- and post-learning tasks included lateral interactions at different target-to-flankers separations (i.e., 2, 3, 4, 8λ) and included a range of spatial frequencies and stimulus durations as well as visual acuity, Vernier acuity, contrast-sensitivity function, and foveal crowding. RESULTS: The results showed that perceptual training reduced the target's contrast-detection thresholds more for the longest target-to-flanker separation (i.e., 8λ). We also found generalization of PL to different stimuli and tasks: contrast sensitivity for both trained and untrained spatial frequencies, visual acuity for Sloan letters, and foveal crowding, and partially for Vernier acuity. Follow-ups after 5-7 months showed not only complete maintenance of PL effects on visual acuity and contrast sensitivity function but also further improvement in these tasks. CONCLUSION: These results suggest that PL improves facilitatory lateral interactions in amblyopic observers, which usually extend over larger separations than in typical foveal vision. The improvement in these basic visual spatial operations leads to a more efficient capability of performing spatial tasks involving high levels of visual processing, possibly due to the refinement of bottom-up and top-down networks of visual areas.

Eye Size, Fovea, and Foraging Ecology in Accipitriform Raptors.

Abstract: Birds with larger eyes are predicted to have higher spatial resolution because of their larger retinal image. Raptors are well known for their acute vision, mediated by their deep central fovea. Because foraging strategies may demand specific visual adaptations, eye size and fovea may differ between species with different foraging ecology. We tested whether predators (actively hunting mobile prey) and carrion eaters (eating dead prey) from the order Accipitriformes differ in eye size, foveal depth, and retinal thickness using spectral domain optical coherence tomography and comparative phylogenetic methods. We found that (1) all studied predators (except one) had a central and a temporal fovea, but all carrion eaters had only the central fovea; (2) eye size scaled with body mass both in predators and carrion eaters; (3) predators had larger eyes relative to body mass and a thicker retina at the edge of the fovea than carrion eaters, but there was no difference in the depth of the central fovea between the groups. Finally, we found that (4) larger eyes generally had a deeper central fovea. These results suggest that the visual system of raptors within the order Accipitriformes may be highly adapted to the foraging strategy, except for the foveal depth, which seems mostly dependent upon the eye size.

Disentangling vision and attention in multiple-object tracking: How crowding and collisions affect gaze anchoring and dual-task performance.

Abstract: Previous studies of multiple-object tracking have shown that gaze behavior is affected by target collisions and target-distractor crowding Therefore, in order to experimentally disentangle this collision-crowding confound, we examined events of target collisions with the bordering frame and crowding with distractors We hypothesized that collisions are particularly demanding for covert attentional processing, whereas crowding particularly challenges peripheral vision Results show that gaze is located closer to targets when they are crowded, as would be expected to reduce negative crowding effects by utilizing the higher spatial acuity of foveal vision However, saccades, which interrupt visual information processing, were instead initiated as a function of target collisions with the bordering frame Consequently, in a dual-task condition that required the detection of target changes, participants more frequently missed changes if they occurred in time intervals around a collision Based on these results, superior performance should be expected if foveal gaze is optimally anchored among crowded targets and if potential target changes are monitored with peripheral vision In addition to the implications for further laboratory research of multiple-object tracking, these findings are relevant to a multitude tasks that require the monitoring of several targets and the simultaneous detection of certain events in the visual periphery, as it is commonly the case, for instance, in sports

Recruitment of Foveal Retinotopic Cortex During Haptic Exploration of Shapes and Actions in the Dark.

Abstract: The role of the early visual cortex and higher-order occipitotemporal cortex has been studied extensively for visual recognition and to a lesser degree for haptic recognition and visually guided actions. Using a slow event-related fMRI experiment, we investigated whether tactile and visual exploration of objects recruit the same “visual” areas (and in the case of visual cortex, the same retinotopic zones) and if these areas show reactivation during delayed actions in the dark toward haptically explored objects (and if so, whether this reactivation might be due to imagery). We examined activation during visual or haptic exploration of objects and action execution (grasping or reaching) separated by an 18 s delay. Twenty-nine human volunteers (13 females) participated in this study. Participants had their eyes open and fixated on a point in the dark. The objects were placed below the fixation point and accordingly visual exploration activated the cuneus, which processes retinotopic locations in the lower visual field. Strikingly, the occipital pole (OP), representing foveal locations, showed higher activation for tactile than visual exploration, although the stimulus was unseen and location in the visual field was peripheral. Moreover, the lateral occipital tactile–visual area (LOtv) showed comparable activation for tactile and visual exploration. Psychophysiological interaction analysis indicated that the OP showed stronger functional connectivity with anterior intraparietal sulcus and LOtv during the haptic than visual exploration of shapes in the dark. After the delay, the cuneus, OP, and LOtv showed reactivation that was independent of the sensory modality used to explore the object. These results show that haptic actions not only activate “visual” areas during object touch, but also that this information appears to be used in guiding grasping actions toward targets after a delay. SIGNIFICANCE STATEMENT Visual presentation of an object activates shape-processing areas and retinotopic locations in early visual areas. Moreover, if the object is grasped in the dark after a delay, these areas show “reactivation.” Here, we show that these areas are also activated and reactivated for haptic object exploration and haptically guided grasping. Touch-related activity occurs not only in the retinotopic location of the visual stimulus, but also at the occipital pole (OP), corresponding to the foveal representation, even though the stimulus was unseen and located peripherally. That is, the same “visual” regions are implicated in both visual and haptic exploration; however, touch also recruits high-acuity central representation within early visual areas during both haptic exploration of objects and subsequent actions toward them. Functional connectivity analysis shows that the OP is more strongly connected with ventral and dorsal stream areas when participants explore an object in the dark than when they view it.

Automatic detection of the foveal center in optical coherence tomography.

Abstract: We propose a method for automatic detection of the foveal center in optical coherence tomography (OCT). The method is based on a pixel-wise classification of all pixels in an OCT volume using a fully convolutional neural network (CNN) with dilated convolution filters. The CNN-architecture contains anisotropic dilated filters and a shortcut connection and has been trained using a dynamic training procedure where the network identifies its own relevant training samples. The performance of the proposed method is evaluated on a data set of 400 OCT scans of patients affected by age-related macular degeneration (AMD) at different severity levels. For 391 scans (97.75%) the method identified the foveal center with a distance to a human reference less than 750 μm, with a mean (± SD) distance of 71 μm ± 107 μm. Two independent observers also annotated the foveal center, with a mean distance to the reference of 57 μm ± 84 μm and 56 μm ± 80 μm, respectively. Furthermore, we evaluate variations to the proposed network architecture and training procedure, providing insight in the characteristics that led to the demonstrated performance of the proposed method.

Arrested Foveal Development in Preterm Eyes: Thickening of the Outer Nuclear Layer and Structural Redistribution Within the Fovea.

Abstract: Purpose The aim of this study was to define landmarks to better characterize foveal microstructure in normal subjects and in preterms with or without signs of immaturity, and to report on thickness changes of outer foveal layers following analysis of optical coherence tomography (OCT) B-scan images. Methods Selected eyes from eight young adults with a history of prematurity (24-33 weeks of gestation) and five controls were imaged using conventional and directional OCT. Retinal layer thickness analysis was performed at selected temporal eccentricities defined by the individual distance between two landmarks for each case, the foveal center and the foveal rim. Results The use of a foveal center and foveal rim landmark transformation enabled comparisons of interindividual B-scans at corresponding landmark positions in both controls and preterms. We found a 20% shorter foveal center to foveal rim distance in preterms with an immature fovea than in controls. Reflectometric and manual segmentation measurements showed increased thickness of inner retinal layers and photoreceptor cell body and outer plexiform layers centrally, but no observable change of photoreceptor inner and outer segment thickness. Conclusions Our landmark-based analysis of OCT images using reflectometry and manual segmentation provides complementary findings in comparisons of normal and immature foveal structures. We show a central thickness increase in the outer nuclear layer, outer plexiform layer, and postreceptor layers in preterms with signs of arrested foveal development. We found no indication of abnormal photoreceptor inner or outer segment development in preterms.

Visual crowding is a combination of an increase of positional uncertainty, source confusion, and featural averaging

Abstract: Although we perceive a richly detailed visual world, our ability to identify individual objects is severely limited in clutter, particularly in peripheral vision. Models of such “crowding” have generally been driven by the phenomenological misidentifications of crowded targets: using stimuli that do not easily combine to form a unique symbol (e.g. letters or objects), observers typically confuse the source of objects and report either the target or a distractor, but when continuous features are used (e.g. orientated gratings or line positions) observers report a feature somewhere between the target and distractor. To reconcile these accounts, we develop a hybrid method of adjustment that allows detailed analysis of these multiple error categories. Observers reported the orientation of a target, under several distractor conditions, by adjusting an identical foveal target. We apply new modelling to quantify whether perceptual reports show evidence of positional uncertainty, source confusion, and featural averaging on a trial-by-trial basis. Our results show that observers make a large proportion of source-confusion errors. However, our study also reveals the distribution of perceptual reports that underlie performance in this crowding task more generally: aggregate errors cannot be neatly labelled because they are heterogeneous and their structure depends on target-distractor distance.

Lateralization of posterior alpha EEG reflects the distribution of spatial attention during saccadic reading.

Abstract: Visuospatial attention is an important mechanism in reading that governs the uptake of information from foveal and parafoveal regions of the visual field. However, the spatiotemporal dynamics of how attention is allocated during eye fixations are not completely understood. The current study explored the use of EEG alpha-band oscillations to investigate the spatial distribution of attention during reading. We reanalyzed two data sets, focusing on the lateralization of alpha activity at posterior scalp sites. In each experiment, participants read short lists of German nouns in two paradigms: either by freely moving their eyes (saccadic reading) or by fixating the screen center while the text moved passively from right to left at the same average speed (RSVP paradigm). In both paradigms, upcoming words were either visible or masked, and foveal processing load was manipulated by varying the words' lexical frequencies. Posterior alpha lateralization revealed a sustained rightward bias of attention during saccadic reading, but not in the RSVP paradigm. Interestingly, alpha lateralization was not influenced by word frequency (foveal load) or preview during the preceding fixation. Hence, alpha did not reflect transient attention shifts within a given fixation. However, in both experiments, we found that in the saccadic reading condition a stronger alpha lateralization shortly before a saccade predicted shorter fixations on the subsequently fixated word. These results indicate that alpha lateralization can serve as a measure of attention deployment and its link to oculomotor behavior in reading.

Automatic detection of the foveal center in optical coherence tomography

Abstract: We propose a method for automatic detection of the foveal center in optical coherence tomography (OCT). The method is based on a pixel-wise classification of all pixels in an OCT volume using a fully convolutional neural network (CNN) with dilated convolution filters. The CNN-architecture contains anisotropic dilated filters and a shortcut connection and has been trained using a dynamic training procedure where the network identifies its own relevant training samples. The performance of the proposed method is evaluated on a data set of 400 OCT scans of patients affected by age-related macular degeneration (AMD) at different severity levels. For 391 scans (97.75%) the method identified the foveal center with a distance to a human reference less than 750 μm, with a mean (± SD) distance of 71 μm ± 107 μm. Two independent observers also annotated the foveal center, with a mean distance to the reference of 57 μm ± 84 μm and 56 μm ± 80 μm, respectively. Furthermore, we evaluate variations to the proposed network architecture and training procedure, providing insight in the characteristics that led to the demonstrated performance of the proposed method.

Numerosity estimation benefits from transsaccadic information integration.

Abstract: Humans achieve a stable and homogeneous representation of their visual environment, although visual processing varies across the visual field. Here we investigated the circumstances under which peripheral and foveal information is integrated for numerosity estimation across saccades. We asked our participants to judge the number of black and white dots on a screen. Information was presented either in the periphery before a saccade, in the fovea after a saccade, or in both areas consecutively to measure transsaccadic integration. In contrast to previous findings, we found an underestimation of numerosity for foveal presentation and an overestimation for peripheral presentation. We used a maximum-likelihood model to predict accuracy and reliability in the transsaccadic condition based on peripheral and foveal values. We found near-optimal integration of peripheral and foveal information, consistently with previous findings about orientation integration. In three consecutive experiments, we disrupted object continuity between the peripheral and foveal presentations to probe the limits of transsaccadic integration. Even for global changes on our numerosity stimuli, no influence of object discontinuity was observed. Overall, our results suggest that transsaccadic integration is a robust mechanism that also works for complex visual features such as numerosity and is operative despite internal or external mismatches between foveal and peripheral information. Transsaccadic integration facilitates an accurate and reliable perception of our environment.

Arthroscopically Assisted Transosseous Foveal Repair of Triangular Fibrocartilage Complex

Abstract: The radioulnar ligament of the triangular fibrocartilage complex (TFCC), especially the deep fibers inserted at the ulnar fovea, is the key component for the distal radioulnar joint (DRUJ) stability. Traumatic injuries to the TFCC foveal insertion would cause DRUJ instability. Traditionally, arthroscopic techniques of the TFCC repair are suturing the ulnar-sided disruption peripherally to the dorsal or ulnar capsule instead of suturing the TFCC to the fovea and thus fail to restore the DRUJ stability if the TFCC is detached from the fovea. Recently, some arthroscopic foveal repair techniques have been reported using a suture anchor or transosseous sutures to address the foveal tear. This technical note describes an arthroscopic transosseous technique to reattach the foveal-disrupted TFCC. A 1.6-mm small osseous tunnel is created on the radial border of the fovea and 4 sutures are passed into the tunnel by using a 16-gauge needle. The TFCC could be sutured arthroscopically with these 4 sutures and be compressed against the fovea. Our technique provides not only a good suture construct for TFCC foveal reattachment but also an anatomic contact surface between the torn TFCC and its foveal footprint for healing. We recommend this technique as an alternative for repairing TFCC foveal tear.

Examining the functionality of peripheral vision: From fundamental understandings to applied sport science

Abstract: In sports, it is important not only to locate gaze on the right location to utilize the high acuity of foveal vision, but also to attend to other objects in the environment without looking directly at them, accordingly, using peripheral vision. Peripheral vision becomes especially important if, for example, the processing of information from more than one location (e.g. players) is decisive in making accurate decisions. Since such decisions generally must be made under high spatio-temporal demands, costly eye-movements might be advantageously avoided by using peripheral vision for information pick-up from multiple cues. In a series of studies, we aimed to translate the demands found in sports and to investigate the functionality of peripheral vision in a well-controlled experimental paradigm, the multiple object tracking (MOT) task. MOT was implemented in a dual task, along with an additional event-detection task. The present article first presents an overview of sport-specific studies focusing on the functionality of peripheral vision and following, summarizes a series of three published MOT studies. These studies show that peripheral vision is used for simultaneous target monitoring and target-change detection and that visual and attentional demands affect gaze anchoring and change-detection rates. Results also reveal a dysfunctionality of saccades, and further suggest an event- and distance-optimized gaze-anchoring position. In the final portion of this article, we derive specific applications for future sports-specific research. Specifically, we suggest to: (a) use dual-task situations in sport-specific settings, such as monitoring multiple players in soccer and playing a pass at specific moments, (b) investigate the costs of saccades in sports situations with high spatio-temporal demands, as in martial arts, and finally, (c) manipulate attentional and visual demands. For each of these avenues of research, we sketch sports-specific experiments currently being conducted in our research group.

The role of extra-foveal processing in 3D imaging.

Abstract: The field of medical image quality has relied on the assumption that metrics of image quality for simple visual detection tasks are a reliable proxy for the more clinically realistic visual search tasks. Rank order of signal detectability across conditions often generalizes from detection to search tasks. Here, we argue that search in 3D images represents a paradigm shift in medical imaging: radiologists typically cannot exhaustively scrutinize all regions of interest with the high acuity fovea requiring detection of signals with extra-foveal areas (visual periphery) of the human retina. We hypothesize that extra-foveal processing can alter the detectability of certain types of signals in medical images with important implications for search in 3D medical images. We compare visual search of two different types of signals in 2D vs. 3D images. We show that a small microcalcification-like signal is more highly detectable than a larger mass-like signal in 2D search, but its detectability largely decreases (relative to the larger signal) in the 3D search task. Utilizing measurements of observer detectability as a function retinal eccentricity and observer eye fixations we can predict the pattern of results in the 2D and 3D search studies. Our findings: 1) suggest that observer performance findings with 2D search might not always generalize to 3D search; 2) motivate the development of a new family of model observers that take into account the inhomogeneous visual processing across the retina (foveated model observers).

Estimating just-noticeable distortion for images/videos in pixel domain

Abstract: Existing pixel-based just noticeable distortion (JND) models only take into account luminance adaptation and texture masking (TM). Similarly, existing discrete cosine transform (DCT) based models do not take into account foveal vision effects and do not estimate TM efficiently. As human visual system (HVS) is not sensitive to distortion below the JND threshold, estimation of the perceptual visibility threshold is widely used in digital and video processing applications. The authors propose a comprehensive and efficient pixel-based JND model incorporating all major factors which contribute to the JND estimation. The evaluation of contrast masking (CM) is done by distinguishing the edge and TM with respect to the entropy masking properties of the HVS. Similarly, the foveal vision effects are also taken into account for the comprehensive estimation of contrast sensitivity function (CSF). Hence, the proposed pixel-based JND model incorporates the spatio-temporal CSF, foveal vision effects, influence of eye-movement, luminance adaptation and CM to be more consistent with human perception. The incorporation of these important factors makes the proposed model the most comprehensive and efficient in the current literature. Psychophysical experiments were performed to test the proposed model. The results show the proposed model comprehensively outperforms other existing models proving its efficiency.

Thickness of retinal layers in the foveas of children with anisometropic amblyopia.

Abstract: Purpose To use highly precise spectral-domain optical coherence tomography (SD-OCT) to determine whether there were structural abnormalities in the layers of different regions of the fovea in children with anisometropic amblyopia. Methods Eighteen children (mean age 7.8 years old; range 5-11 years) with unilateral anisometropic amblyopia and 18 age-matched control subjects participated. Foveal thickness was measured with an enhanced depth imaging system, SD-OCT and segmented into layers using custom developed software. The thickness of each layer of the fovea was compared among amblyopic eyes, fellow eyes and control eyes with optical magnification correction for axial length and statistical correction for age and sex. Results The total thickness and each intra-ocular layer of the central fovea were the same for each group. However, the amblyopic eyes were significantly thicker than the normal control eyes in 2 of 4 quadrants of the peripheral retina. Exploring intra-retinal layers in these two quadrants, the nasal nerve fiber layer (NFL) and inferior inner nuclear layer (INL)were significantly thicker in amblyopic eyes than in control eyes (p = 0.01 and 0.012, respectively, by ANCOVA). Conclusion The SD-OCT data revealed marginal differences in some foveal layers at peripheral locations and indicated that structural differences might exist between individuals with amblyopia and visually normal control subjects. However, the differences were scattered and represented no identifiable pattern. More studies with large samples and precise locations of the retinal layers must be performed to extend the present results.

Visual acuity and signal color pattern in an Anolis lizard.

Abstract: Anolis lizards communicate with colorful dewlaps that often include detailed patterns. We measured the visual acuity of Anolis sagrei. Lizards viewed a checkerboard pattern of red and yellow–green squares that were too small to resolve, and thus appeared uniform in color. We quickly replaced the center portion of the display with a pattern of larger squares. If the new pattern could be resolved, the lizards perceived a change in color and reflexively shifted their gaze toward the target. The acuity threshold was 1.21 cycles deg −1 . We also calculated acuity based on published anatomical data for Anolis carolinensis . It was similar to that of A. sagrei for the visual periphery. Foveal acuity was 10 times greater. We approximated the effects of viewing conditions on the visibility of fine details of a conspecific9s dewlap. For peripheral vision, no detailed patterns were visible at ≥0.5 m. For foveal vision, color-pattern details were visible at 1.0 m.