Vision, Volume 2, Issue 1 (March 2018) – 15 articles

Neovascular age-related macular degeneration is a leading cause of vision loss among the aging population. The current standard of care to treat neovascular age-related macular degeneration is inhibiting vascular endothelial growth factor (VEGF) through intravitreal injections. Recent studies have demonstrated that the tyrosine kinase with immunoglobulin-like and epidermal growth factor-like domains 2 (Tie2) pathway also plays a critical role in angiogenesis and vascular stability. Additionally, newly developed treatment delivery systems have been designed to greatly reduce the frequency of injections. In targeting the Tie2 pathway and utilizing a sustained release delivery system, patients may experience improved visual outcomes and a reduced burden of treatment. Full article

Many visual effects are believed to be processed at several functional and anatomical levels of cortical processing. Determining if and how the levels contribute differentially to these effects is a leading problem in visual perception and visual neuroscience. We review and analyze a combination of extant psychophysical findings in the context of neurophysiological and brain-imaging results. Specifically using findings relating to visual illusions, crowding, and masking as exemplary cases, we develop a theoretical rationale for showing how relative levels of cortical processing contributing to these effects can already be deduced from the psychophysically determined functions relating respectively the illusory, crowding and masking strengths to the contrast of the illusion inducers, of the flankers producing the crowding, and of the mask. The wider implications of this rationale show how it can help to settle or clarify theoretical and interpretive inconsistencies and how it can further psychophysical, brain-recording and brain-imaging research geared to explore the relative functional and cortical levels at which conscious and unconscious processing of visual information occur. Our approach also allows us to make some specific predictions for future studies, whose results will provide empirical tests of its validity. Full article

Understanding how the eyes work together to determine the direction of objects provided the impetus for examining integration of signals from the ears to locate sounds. However, the advantages of having two eyes were recorded long before those for two ears were appreciated. In part, this reflects the marked differences in how we can compare perception with one or two organs. It is easier to close one eye and examine monocular vision than to “close” one ear and study monaural hearing. Moreover, we can move our eyes either in the same or in opposite directions, but humans have no equivalent means of moving the ears in unison. Studies of binocular single vision can be traced back over two thousand years and they were implicitly concerned with visual directions from each eye. The location of any point in visual or auditory space can be described by specifying its direction and distance, from the vantage point of an observer. From the late 18th century experiments indicated that binocular direction involved an eye movement component and experimental studies of binaural direction commenced slightly later. However, these early binocular and binaural experiments were not incorporated into theoretical accounts until almost a century later. The early history of research on visual direction with two eyes is contrasted to that on auditory direction with two ears. Full article

An eye-of-origin singleton, e.g., a bar shown to the left eye among many other bars shown to the right eye, can capture attention and gaze exogenously or reflexively, even when it appears identical to other visual input items in the scene and when the eye-of-origin feature is irrelevant to the observer’s task. Defining saliency as the strength of exogenous attraction to attention, we say that this eye-of-origin singleton, or its visual location, is salient. Defining the ocularity of a visual input item as the relative difference between its left-eye input and its right-eye input, this paper shows the general case that an ocularity singleton is also salient. For example, a binocular input item among monocular input items is salient, so is a left-eye-dominant input item (e.g., a bar with a higher input contrast to the left eye than to the right eye) among right-eye-dominant items. Saliency by unique input ocularity is analogous to saliency by unique input colour (e.g., a red item among green ones), as colour is determined by the relative difference(s) between visual inputs to different photoreceptor cones. Just as a smaller colour difference between a colour singleton and background items makes this singleton less salient, so does a smaller ocularity difference between an ocularity singleton and background items. While a salient colour difference is highly visible, a salient ocularity difference is often perceptually invisible in some cases and discouraging gaze shifts towards it in other cases, making its behavioural manifestation not as apparent. Saliency by ocularity contrast provides another support to the idea that the primary visual cortex creates a bottom-up saliency map to guide attention exogenously. Full article

Understanding the mental states of our social partners allows us to successfully interact with the world around us. Mental state attributions are argued to underpin social attention, and have been shown to modulate attentional orienting to social cues. However, recent research has disputed this claim, arguing that this effect may arise as an unintentional side effect of study design, rather than through the involvement of mentalising processes. This study therefore aimed to establish whether the mediation of gaze cueing by mental state attributions generalises beyond the specific experimental paradigm used in previous research. The current study used a gaze cueing paradigm within a change detection task, and the gaze cue was manipulated such that participants were aware that the cue-agent was only able to ‘see’ in one condition. The results revealed that participants were influenced by the mental state of the cue-agent, and were significantly better at identifying if a change had occurred on valid trials when they believed the cue-agent could ‘see’. The computation of the cue-agent’s mental state therefore mediated the gaze cueing effect, demonstrating that the modulation of gaze cueing by mental state attributions generalises to other experimental paradigms. Full article

The excitation of the visual system increases with increasing retinal illumination. At the same time, the sensitivity of the system decreases (light adaptation). Higher excitation automatically results in a lower sensitivity. This study investigates whether this antagonistic relationship between excitation and sensitivity also applies to the dynamic case, that is, during the transition to a higher excitation level after a sudden increase in retinal illuminance. For this purpose, the courses of the subjective and the electroretinographic threshold in the transitional period during and after a step of the adaptation illuminance were investigated by means of a special light-stimulation system. The investigation was carried out on 9 (subjective threshold) and 12 (electroretinographic threshold) subjects. As a measure of the course of the excitation during this time, the response ERG on the adaptation step was recorded. With the step in adaptation light, the thresholds show a rapid increase, which starts already about 0.1 s before the step. This is followed, within the next second, by a threshold decrease to a new plateau above the initial level. The comparison between the response ERG on the adaptation step and the course of the electroretinographic increment threshold during this time shows a broad agreement between the two courses. Thus, it can be assumed that the sensitivity of the visual system also follows the excitation in the dynamic case. In addition, the investigation shows that the glare experienced after a step in illuminance apparently shows great subjective differences. Full article

Observers automatically orient to a sudden change in the environment. This is demonstrated experimentally using exogenous cues, which prioritize the analysis of subsequent targets appearing nearby. This effect has been attributed to the computation of saliency, obtained by combining features specific signals, which then feed back to drive attention to the salient location. An alternative possibility is that cueing directly effects target-evoked sensory responses in a feed-forward manner. We examined the effects of luminance and equiluminant color cues in a dual task paradigm, which required both a motion and a color discrimination. Equiluminant color cues improved color discrimination more than luminance cues, but luminance cues improved motion discrimination more than equiluminant color cues. This suggests that the effects of exogenous cues are dimensionally specific and may not depend entirely on the computation of a dimension general saliency signal. Full article

Control of visual attention by auditory stimuli is explored in seven previously unpublished experiments that were presented at conferences in the late 1980s. Reaction time (RT) to luminance targets was found to be affected by the spatial congruence between the target and a preceding or simultaneous, and non-informative, auditory event, suggesting that localizable auditory stimuli exogenously (rapidly and automatically) capture visual attention. These cuing effects were obtained in the absence of eye movements and do not appear to be mediated merely by criterion adjustments. When the information value of the auditory event was placed in conflict with its location (i.e., a tone on the right indicated that the visual target was likely to appear on the left), it was found that at short stimulus onset asynchronies (SOAs) reaction time (RT) was faster for targets at the stimulated location, an effect that disappeared within 500 ms and was reversed by 1000 ms. This demonstrates that it requires over 500 ms for endogenous orienting in response to probabilistic information about target location to overcome the powerful exogenous control of visual attention by localizable auditory stimulation. Simple RT to auditory stimuli was unaffected by the spatial congruence of a preceding or simultaneous visual stimulus. When uninformative, neither pitch contours (rising/falling tones) nor pitch (high/low tones) produced significant visual orienting along the vertical midline. When the direction of a pitch contour indicated the likely location of a visual target, participants were able to shift their attention if the relation between the natural meaning and the probabilistic information was compatible (e.g., rising contour signaled that a upper target was likely) but not when it was incompatible. The relation of these 30-year-old experiments to contemporary findings and ideas is discussed. Full article

Individuals with migraine show differences in visual perception compared to control groups. It has been suggested that differences in lateral interactions between neurons might account for some of these differences. This study seeks to further establish the strength and spatial extent of excitatory and inhibitory interactions in migraine-with-aura using a classic lateral masking task. Observers indicated which of two intervals contained a centrally presented, vertical Gabor target of varying contrast. In separate blocks of trials, the target was presented alone or was flanked by two additional collinear, high contrast Gabors. Flanker distances varied between 1 and 12 wavelengths of the Gabor stimuli. Overall, contrast thresholds for the migraine group were lower than those in the control group. There was no difference in the degree of lateral interaction in the migraine group. These results are consistent with the previous work showing enhanced contrast sensitivity in migraine-with-aura for small, rapidly presented targets, and they suggest that impaired performance in global perceptual tasks in migraine may be attributed to difficulties in segmenting relevant from irrelevant features, rather than altered local mechanisms. Full article

Data from studies employing the dot-perspective task have been used to support the theory that humans are capable of automatically computing the visual perspective of other individuals. Recent work has challenged this interpretation, claiming instead that the results may arise through the automatic reorienting of attention triggered by observed head and gaze cues. The two experiments reported here offer a stronger test of the perspective taking account by replacing the computer-generated avatars used in previous research with, respectively, photo-realistic stimuli and socially co-present individuals in a “live”, face-to-face version of the task. In each study observers were faster to judge the number of dots in a display when either a digitized image depicting a human “gazer” (Experiment 1), or a socially co-present gazer (Experiment 2) could see the same number of dots as the observer, than when the number of dots visible to each was different. However, in both experiments this effect was also obtained in conditions where barriers clearly occluded the gazers’ view of the target dots so that the perspectives of participants and gazers were always different. These results offer no support for the idea that participants are engaged in spontaneous perspective taking in the dot perspective task. It is argued that, instead, the results are likely caused by a spontaneous redirection of a viewer’s attention by the observed gazes, which is unlikely to involve representations of the gazer’s mental state. Full article

A retrospective study of 176 treatment-naïve eyes with neovascular age-related macular degeneration (nAMD) that had undergone intravitreal aflibercept treatment (2.0 mg, 7–8 times over one year) was performed to correlate the effect of aflibercept on the morphological features of nAMD—subretinal hyper-reflective material (SHRM), pigment epithelial detachment (PED), subretinal fluid (SRF), and intraretinal fluid (IRF)—with visual acuity at baseline and at one year. Spectral-Domain Optical Coherence Tomography (SD-OCT) images and best-corrected visual acuity (BCVA) at baseline and at one year were obtained. The relationship between visual acuity and the presence of morphological features at baseline and at one year was statistically analysed. The proportion of eyes with PED (p = 0.01), SRF (p ≤ 0.001), and IRF (p ≤ 0.001) reduced at one year. SHRM (p = 0.002) and IRF (p = 0.0001) were associated with poorer baseline BCVA. The presence of SRF at baseline was associated with better baseline BCVA (p = 0.004) and 5.3 letters of improvement of BCVA after one year of treatment (p = 0.0001). For each letter increase in BCVA at baseline, 0.25 fewer letters were gained in BCVA at one year. While aflibercept can improve morphological abnormalities in nAMD, this is not always accompanied by a corresponding improvement in visual acuity. Full article

AMD does not just affect the retina. It severely affects people’s lives. Paying attention to this aspect will only become more important as the population ages and more otherwise healthy individuals become affected. This paper will discuss the need for teamwork to overcome the difference between medical care, which addresses the causes of AMD, and rehabilitative care, which addresses the consequences. Different aspects and different degrees of vision loss ask for different interventions. Loss of detailed vision can be addressed by a wide variety of magnification devices. The means to address this aspect are well recognized. Surround vision is largely processed pre-attentively. Its loss cannot be remediated by devices, but must be addressed through patient education to bring previously subconscious reactions to conscious awareness. Loss of contrast vision is an aspect that is not sufficiently studied. It is important for early detection, and for the safety of the patient. When the eye condition cannot be modified, environmental modifications provide the most effective remediation. Full article

Experiments demonstrating level-1 visual perspective-taking have been interpreted as providing important evidence for ‘implicit mentalising’—the ability to track simple mental states in a fast and efficient manner. However, this interpretation has been contested by a rival ‘submentalising’ account that proposes that these experiments can be explained by the general purpose mechanisms responsible for attentional orienting. Here, we aim to discriminate between these competing accounts by examining whether a gaze aversion manipulation expected to enhance attention orienting would have similar effects on both perspective-taking and attention orienting tasks. Gaze aversion was operationalised by manipulating head position relative to torso of the avatar figures employed in two experiments (gaze-averted vs. gaze-maintained). Experiment 1 used a Posner cueing task to establish that gaze aversion enhanced attention orienting cued by these avatars. Using the avatar task, Experiment 2 revealed level-1 visual perspective-taking effects of equivalent magnitude for gaze-averted and gaze-maintained conditions. These results indicate that gaze aversion moderated attention orienting but not perspective-taking. This dissociation in performance favours implicit mentalising by casting doubt on the submentalising account. It further constrains theorising by implying that attention orienting is not integral to the system permitting the relatively automatic tracking of mental states. Full article

Myalgic encephalomyelitis (ME) is a devastating disorder marked by debilitating fatigue. It not well understood and its diagnosis is controversial. It is very important therefore that significant clinical features are investigated. Visual symptoms in ME represent a group of distinct, quantifiable, clinical features that could significantly improve diagnosis and provide insights into underlying pathology. The purpose of the present study was therefore to explore the effect of ME on spatial windows of visibility using the spatial contrast sensitivity function. Contrast sensitivity was determined for stationary luminance-defined sinusoidal gratings spanning a five-octave range of spatial frequencies (0.5 to 16 c/deg) in a group of 19 individuals with ME and a group of 19 matched (age, gender) controls. Compared to controls, the ME group exhibited a restricted spatial window of visibility for encoding stimulus contrast. This was characterised principally by a contrast sensitivity deficit at lower spatial frequencies and a narrower bandwidth. Our findings suggest that contrast sensitivity deficits may represent a visual marker of ME, and be indicative of abnormal visual processing at the level of the retina and in the cortical and subcortical visual pathways. Full article