Attention in redundancy masking.

Peripheral vision is limited due to several factors, such as visual resolution, crowding, and attention. When attention is not directed towards a stimulus, detection, discrimination, and identification are often compromised. Recent studies have found a new phenomenon that strongly limits peripheral vision, "redundancy masking".

Alterations to foveal crowding with microsaccade preparation.

Visual stimuli presented around the time of a saccade have been shown to be perceived differently by the visual system, including a reduction in the harmful impact of flankers (crowding). However, whether the effects observed are due strictly to crowding remains controversial, and the effects have only been measured with large saccades in peripheral vision. Here we investigate how crowded stimuli placed 20 arc minutes from the center of gaze are affected by an upcoming microsaccade.

Impact of monocular vs. binocular contrast and blur on the range of functional stereopsis.

Stereopsis depends on the smallest stereo threshold (lower limit) and the upper fusion limit. While studies have shown that the lower limit worsens with reduced contrast and blur, more strongly in monocular than in binocular conditions, the effect on the upper limit remains uncertain. Here, we assess the impact of contrast and blur on the range of the disparity sensitivity function (DSF) in a stereo letter recognition task.

Case Report: When Two Is Worse Than One-Stereo Imbalance in a Case of Wavefront-guided Scleral Lenses.

Significance: Wavefront-guided scleral lenses (WGSLs) reduce visually debilitating residual higher-order aberrations. Although reduced higher-order aberrations lead to improvement in monocular high-contrast visual acuity (VA), the success of the lenses in everyday life depends on additional factors such as retinal contrast, binocular balance, and stereoacuity.

Purpose: This report describes a case where WGSLs provided improved monocular vision compared with scleral lenses (SLs) but reduced binocularity and stereoacuity.

Microsaccadic correlates of covert attention and crowding.

Spatial crowding occurs when an object is cluttered among other objects in space and is a ubiquitous factor affecting object recognition in the peripheral visual field. Crowding is typically tested by presenting crowded stimuli at an eccentric location while having observers fixate at a point in space. However, even during fixation, our eyes are not perfectly steady but instead make small-scale eye movements (microsaccades) that have recently been suggested to be affected by shifts in attentional allocation.

Assessment of depth perception with a comprehensive disparity defined letter test: A pilot study.

Current clinical tests mostly assess stereopsis with crossed disparity at near. These tests are designed with fine targets (high spatial frequency) and may fail to capture the "functional stereopsis" in real-world scenes, which consist of a range of spatial frequencies (SFs). We developed a stereo letter test that can assess crossed and uncrossed stereoacuity at near and far, at different SFs defined by the letter size.

Atypical visual field asymmetries in redundancy masking.

Redundancy masking is the reduction of the perceived number of items in repeating patterns. It shares a number of characteristics with crowding, the impairment of target identification in visual clutter. Crowding strongly depends on the location of the target in the visual field.

Cortical distance unifies the extent of parafoveal contour interactions.

It is well known that crowding, the disruptive influence of flanking items on identification of targets, is the primary limiting factor to object identification in the periphery, while limits in the fovea are more determined by the ability to resolve individual items. Whether this is a dichotomous or merely a quantitative difference, and the transition between these two regimes, has remained unexplained. Here, using an adaptive optics system for optimal control of optical and stimulus factors, we measured threshold acuity for identification of Tumbling Es flanked by bars at a variety of flanker spacings and eight eccentricities in the parafovea.

Clinical applications of personalising the neural components of visual image quality metrics for individual eyes.

Purpose: Eyecare is evolving increasingly personalised corrections and increasingly personalised evaluations of corrections on-eye. This report describes individualising optical and neural components of the VSX (visual Strehl) metric and evaluates personalisation using two clinical applications. (1) Better understanding visual experience: While VSX tracks visual performance in typical eyes, non-individualised metrics underestimated visual performance in highly aberrated eyes - could this be understood by personalising metrics? (2) Metric-optimised objective spherocylindrical refractions in typical and atypical eyes have used neural weighting functions of typical eyes - will personalisation affect the outcome in clinical 0.

The generality of the critical spacing for crowded optotypes: From Bouma to the 21st century.

It is rare to find a crowding manuscript that fails to mention "Bouma's law," the rule of thumb stating that flankers within a distance of about one half of the target eccentricity will induce crowding. Here we investigate the generality of this rule (even for just optotypes), the factors that modulate the critical spacing, and the evidence for the rule in Bouma's own data. We explore these questions by reanalyzing a variety of studies from the literature, running several new control experiments, and by utilizing a model that unifies flanked identification measurements between psychophysical paradigms.

Stimulus dependence of interocular suppression.

Interocular suppression is the phenomenon in which the signal from one eye inhibits the other eye in the presence of dissimilar images. Various clinical and laboratory-based tests have been used to assess suppression, which vary in color, contrast, and stimulus size. These stimulus variations may yield different spatial extents of suppression, which makes it difficult to compare the outcomes.

Fundus motion during mfERG testing.

Purpose: The purpose of this study was to assess eye movements during a multifocal ERG (mfERG) recording. This study evaluated the relationship between bivariate contour ellipse areas (BCEAs), mfERG amplitudes (Amps) and mfERG implicit times (ITs) with repeat testing and experienced subjects.

Methods: Thirty subjects were selected (15 experienced to ocular procedures and 15 novices).

Geometrically restricted image descriptors: A method to capture the appearance of shape.

Shape perception varies depending on many factors. For example, presenting a stimulus in the periphery often yields a different appearance compared with its foveal presentation. However, how exactly shape appearance is altered under different conditions remains elusive.

Hidden by bias: how standard psychophysical procedures conceal crucial aspects of peripheral visual appearance.

The perception of a target depends on other stimuli surrounding it in time and space. This contextual modulation is ubiquitous in visual perception, and is usually quantified by measuring performance on sets of highly similar stimuli. Implicit or explicit comparisons among the stimuli may, however, inadvertently bias responses and conceal strong variability of target appearance.

Orientation-specific long-term neural adaptation of the visual system in keratoconus.

Eyes with the corneal ectasia keratoconus have performed better than expected (e.g. visual acuity) given their elevated levels of higher-order aberrations that cause rotationally asymmetric retinal blur.

Effect of cone spectral topography on chromatic detection sensitivity.

The spatial and spectral topography of the cone mosaic set the limits for detection and discrimination of chromatic sinewave gratings. Here, we sought to compare the spatial characteristics of mechanisms mediating hue perception against those mediating chromatic detection in individuals with known spectral topography and with optical aberrations removed with adaptive optics. Chromatic detection sensitivity in general exceeded previous measurements and decreased monotonically for increasingly skewed cone spectral compositions.

Redundancy masking: The loss of repeated items in crowded peripheral vision.

Crowding is the deterioration of target identification in the presence of neighboring objects. Recent studies using appearance-based methods showed that the perceived number of target elements is often diminished in crowding. Here we introduce a related type of diminishment in repeating patterns (sets of parallel lines), which we term "redundancy masking.

Asymmetries of reading eye movements in simulated central vision loss.

Patients with central vision loss are forced to use an eccentric retinal location as a substitute for the fovea, called a preferred retinal locus, or PRL. Clinical studies have shown that patients habitually choose a PRL located either to the left, and/or below the scotoma in the visual field. The position to the right of the scotoma is almost never chosen, even though this would be theoretically more suitable for reading, since the scotoma no longer blocks the upcoming text.

Emergent features break the rules of crowding.

Crowding is the deleterious influence of surrounding objects (flankers) on target identification. A central rule of crowding is that it is stronger when the target and the flankers are similar. Here, we show in three experiments how emergent features break this rule.

Feature contingencies when reading letter strings.

Many models posit the use of distinctive spatial features to recognize letters of the alphabet, a fundamental component of reading. It has also been hypothesized that when letters are in close proximity, visual crowding may cause features to mislocalize between nearby letters, causing identification errors. Here, we took a data-driven approach to investigate these aspects of textual processing.

Emergent features in the crowding zone: When target-flanker grouping surmounts crowding.

Crowding is the impairment of target identification when the target is surrounded by nearby flankers. Two hallmarks of crowding are that it is stronger when the flankers are close to the target and when the target strongly groups with the flankers. Here we show the opposite of both.

Foveal Crowding Resolved.

Crowding is the substantial interference of neighboring items on target identification. Crowding with letter stimuli has been studied primarily in the visual periphery, with conflicting results for foveal stimuli. While a cortical locus for peripheral crowding is well established (with a large spatial extent up to half of the target eccentricity), disentangling the contributing factors in the fovea is more challenging due to optical limitations.

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

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.

Crowding in the S-cone pathway.

The spatial extent of interference from nearby object or contours (the critical spacing of "crowding") has been thoroughly characterized across the visual field, typically using high contrast achromatic stimuli. However, attempts to link this measure with known properties of physiological pathways have been inconclusive. The S-cone pathway, with its ease of psychophysical isolation and known anatomical characteristics, offers a unique tool to gain additional insights into crowding.

Changes across the psychometric function following perceptual learning of an RSVP reading task.

Several recent studies have shown that perceptual learning can result in improvements in reading speed for people with macular disease (e.g., Chung, 2011; Tarita-Nistor et al.