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Contrast sensitivity for a Gabor signal is affected by collinear high-contrast Gabor flankers. The flankers reduce (inhibitory effect) or increase (facilitatory effect) sensitivity, at short (2λ) and intermediate (6λ) target-to-flanker separation respectively. We investigated whether these inhibitory/facilitatory sensitivity effects are modulated by transcranial random noise stimulation (tRNS) applied to the occipital and frontal cortex of human observers during task performance. Signal detection theory was used to measure sensitivity ( d ’) and the Criterion (C) in a contrast detection task, performed with sham or tRNS applied over the occipital or the frontal cortex. After occipital stimulation results show a tRNS-dependent increased sensitivity for the single Gabor signal of low but not high contrast. Moreover, results suggest a dissociation of the tRNS effect when the Gabor signal is presented with the flankers, consisting in a general increased sensitivity at 2λ where the flankers had an inhibitory effect (reduction of inhibition) and a decreased sensitivity at 6λ where the flankers had a facilitatory effect on the Gabor signal (reduction of facilitation). After a frontal stimulation, no specific effect of the tRNS was found. We account for these complex interactions between tRNS and flankers by assuming that tRNS not only enhances feedforward input from the Gabor signal to the cortex, but also enhances the excitatory or inhibitory lateral intracortical input from the flankers. The boosted lateral input depends on the excitation-inhibition (E/I) ratio, namely when the lateral input is weak, it is boosted by tRNS with consequent modification of the contrast-dependent E/I ratio.

When we see an optical pattern that has a gradient of the size and/or density of its texture elements, we often perceive a surface that is slanted in depth. Our inquiry was to ask whether the effect of a texture gradient depends on the direction of the gradient (ground, ceiling, and sidewall patterns) or on the position of the observer’s head (upward, forward, or downward). In Experiments 1 and 2 , a total of 63 observers judged the apparent slant of polka-dot, grid, or flagstone patterns; regardless of head position, the ground patterns were judged to be closer to the frontal plane than were the other patterns. This means that there is a visual anisotropy in head-centric slant perception. To explain this result, we assumed accumulated positional effects of size contrast—that is, a tendency to perceive the size of the upper part of visual space to be larger than the size of the lower part. This hypothesis was examined in two subsequent experiments by reducing the size contrast among the texture elements. When 23 observers viewed regularly arranged same-sized-dot patterns with gradients of the interdot interval and with linear perspective of the dotted lines, anisotropic effects were still detected. When 22 observers viewed dynamic random-dot patterns with gradients of velocity, the anisotropic effects mentioned above were removed in many cases, and the ceiling patterns were sometimes judged to be less slanted than the other patterns. These results partially support the size contrast hypothesis and were compared with the predictions from other hypotheses.

Alzheimer's Disease (AD) can cause degeneration in the retina and optic nerve either directly, as a result of amyloid beta deposits, or secondarily, as a result of the degradation of the visual cortex. These effects raise the possibility that tracking ophthalmologic changes in the retina can be used to assess neurodegeneration in AD. This study aimed to detect retinal changes and associated functional changes in three groups of patients consisting of AD patients with mild disease, AD patients with moderate disease and healthy controls by using non-invasive psychophysical ophthalmological tests and optical coherence tomography (OCT). We included 39 patients with mild AD, 21 patients with moderate AD and 40 age-matched healthy controls. Both patients and controls were ophthalmologically healthy. Visual acuity, contrast sensitivity, colour perception, visual integration, and choroidal thicknesses were measured. In addition, OCT and OCT angiography (OCTA) were applied. Visual acuity, contrast sensitivity, colour perception, and visual integration were significantly lower in AD patients than in healthy controls. Compared to healthy controls, macular thinning in the central region was significant in the mild AD patients, while macular thickening in the central region was found in the moderate AD group. The analysis of macular layers revealed significant thinning of the retinal nerve fibre layer, the ganglion cell layer and the outer plexiform layer in AD patients relative to controls. Conversely, significant thickening was observed in the outer nuclear layer of the patients. However, mild AD was associated with significant thinning of the subfovea and the nasal and inferior sectors of the choroid. Significant superonasal and inferotemporal peripapillary thinning was observed in patients with moderate disease. The first changes in the mild AD patients appear in the psychophysical tests and in the central macula with a decrease in the central retinal thickness. When there was a disease progression to moderate AD, psychophysical tests remained stable with respect to the decrease in mild AD, but significant thinning in the peripapillary retina and thickening in the central retina appeared. The presence of AD is best indicated based on contrast sensitivity.

To evaluate and compare the clinical outcomes with an aspheric monofocal intraocular lens (IOL) and an extended range of vision (ERV) IOL based on achromatic diffractive technology. This was a prospective comparative study including 80 eyes undergoing cataract surgery with implantation of the monofocal Tecnis ZCB00 IOL (Abbott Medical Optics Inc., Santa Ana, CA) (monofocal group: 30 eyes of 15 patients) or the ERV Tecnis Symfony IOL (Abbott Medical Optics, Inc.) (ERV group: 50 eyes of 25 patients). Visual, refractive, contrast sensitivity, defocus curve, ocular optical quality (Optical Quality Analysis System; Visiometrics SL, Terrassa, Spain), and quality of life (National Eye Institute Refractive Error Quality of Life Instrument 42 Questionnaire) outcomes were evaluated during a 3-month follow-up. Significantly better postoperative uncorrected monocular and binocular distance (UDVA), intermediate (UIVA), and near (UNVA) visual acuities were found in the ERV group (P ≥ .013). Postoperative spherical equivalent was within ±1.00 diopters in 94% and 100% of eyes in the ERV and the monofocal groups, respectively. Binocular UIVA and UNVA of 0.20 or better (Snellen 20/30) were observed in all cases in the ERV group and in 13.3% and 6.7% of eyes of the monofocal group, respectively. No significant differences among groups were observed in contrast sensitivity (P ≥ .156) or ocular optical quality parameters (P ≥ .084). In the monocular defocus curve, all visual acuities were better in the ERV group (P ≤ .002), except for the +0.50-diopter defocus level (P = .367). Significantly better scores were obtained for dependence on correction (P = .003) and suboptimal correction (P = .038) subscales in the ERV group. The extended range of vision IOL provides better distance, intermediate, and near visual acuity than the aspheric monofocal IOL, while maintaining the same level of visual quality. [J Refract Surg. 2016;32(7):436-442.].

Impairments of visual function abilities, such as visual acuity and contrast sensitivity, can negatively impact our ability to perform manual prehension tasks. Despite the clear link between visual input and motor output, there is still limited understanding of how visual function deficits affect hand motor behavior. This study aimed to explore the impact of different levels of visual function degradation, specifically in terms of visual acuity and contrast sensitivity, on the reach and grasp components of manual prehension. To this end, visual function degradation was induced in young participants with normal vision using five different densities of Bangerter occlusion foils. Participants were instructed to perform a natural and accurate reach-to-grasp task towards a cylindrical object with two different diameters (3.5 or 7 cm) and positioned at two distances (25 or 50 cm). The effects of visual function degradation, object size, and distance were evaluated by recording the position and trajectory of the right hand using an optoelectronic motion capture system. Three-dimensional kinematic analysis revealed that visual function degradation in normal-sighted individuals directly altered the reach and grasp components of prehension movements. These alterations included longer movement durations, lower velocity and acceleration profiles, slower deceleration phases, over-scaled hand grip apertures, and greater trajectory deviations. The effects were dependent on the level of visual degradation induced and the intrinsic (size) and extrinsic (distance) object properties. Reductions exceeding 70% in visual acuity and 55% in CS had the most pronounced impact on prehension components. However, subtle reductions greater than 30% in visual acuity and 15% in contrast sensitivity were sufficient to trigger compensatory mechanisms. These findings provide further understanding of how visual function degradation affects prehension movement strategies, highlighting the crucial relationship between visual feedback quality and object properties in the motor online control of the transport, manipulation and spatial components. Our results offer new insights into the implications of visual impairments on manual prehension movements.

Abstract Background and Hypothesis Understanding perceptual alterations in mental disorders can help uncover neural and computational anomalies. In schizophrenia, perceptual alterations have been reported for many visual features, including a deficit in contrast sensitivity, a key measure of visual function. The evidence supporting this deficit, however, has not been comprehensively synthesized. Study Design We conducted a systematic review and meta-analysis of studies measuring contrast sensitivity in individuals with schizophrenia and healthy controls. Our search identified 46 studies, of which 43 focused on chronic patients. Study Results We found that patients with chronic schizophrenia have reduced contrast sensitivity (g = 0.74; 95% CI, 0.55 to 0.93; P = 8.2 × 10−10). However, we found evidence that the deficit could be driven by medication. Additionally, none of the studies estimated attentional lapses, leaving it uncertain whether a potentially higher frequency of lapses in patients contributes to the observed deficit. Furthermore, only two studies comprehensively assessed visual acuity, complicating the understanding of the role of spatial frequency in the observed deficit. Conclusions While we identified a robust deficit in contrast sensitivity among chronic schizophrenia patients, the influence of attentional lapses and medication on this impairment remains unclear. We make several suggestions for future research to clarify the underlying mechanisms contributing to this deficit.

In the animal kingdom, threat information is perceived mainly through vision. The subcortical visual pathway plays a critical role in the rapid processing of visual information-induced fear, and triggers a response. Looming-evoked behavior in rodents, mimicking response to aerial predators, allowed identify the neural circuitry underlying instinctive defensive behaviors; however, the influence of disk/background contrast on the looming-induced behavioral response has not been examined, either in rats or mice. We studied the influence of the dark disk/gray background contrast in the type of rat and mouse defensive behavior in the looming arena, and we showed that rat and mouse response as a function of disk/background contrast adjusted to a sigmoid-like relationship. Both sex and age biased the contrast-dependent response, which was dampened in rats submitted to retinal unilateral or bilateral ischemia. Moreover, using genetically manipulated mice, we showed that the three type of photoresponsive retinal cells (i.e., cones, rods, and intrinsically photoresponsive retinal ganglion cells (ipRGCs)), participate in the contrast-dependent response, following this hierarchy: cones > > rods > >  > ipRGCs. The cone and rod involvement was confirmed using a mouse model of unilateral non-exudative age-related macular degeneration, which only damages canonical photoreceptors and significantly decreased the contrast sensitivity in the looming arena.

This study finds that playing an action video game results in improvements in visual contrast sensitivity. These improvements do not happen for an equivalent group who played a non-action video game. The contrast sensitivity function (CSF) is routinely assessed in clinical evaluation of vision and is the primary limiting factor in how well one sees. CSF improvements are typically brought about by correction of the optics of the eye with eyeglasses, contact lenses or surgery. We found that the very act of action video game playing also enhanced contrast sensitivity, providing a complementary route to eyesight improvement.

Medaka fish ( Oryzias latipes ) is a powerful model to study genetics underlying the developmental and functional traits of the vertebrate visual system. We established a simple and high-throughput optomotor response (OMR) assay utilizing medaka larvae to study visual functions including visual acuity and contrast sensitivity. Our assay presents multiple adjustable stripes in motion to individual fish in a linear arena. For that the OMR assay employs a tablet display and the Fish Stripes software to adjust speed, width, color, and contrast of the stripes. Our results demonstrated that optomotor responses were robustly induced by black and white stripes presented from below in the linear-pool-arena. We detected robust strain specific differences in the OMR when comparing long established medaka inbred strains. We observed an interesting training effect upon the initial exposure of larvae to thick stripes, which allowed them to better respond to narrower stripes. The OMR setup and protocol presented here provide an efficient tool for quantitative phenotype mapping, addressing visual acuity, trainability of cortical neurons, color sensitivity, locomotor response, retinal regeneration and others. Our open-source setup presented here provides a crucial prerequisite for ultimately addressing the genetic basis of those processes.

To assess visual outcomes and patient satisfaction for trifocal and extended depth of focus (EDOF) intraocular lenses (IOLs) compared to monofocal IOLs with and without monovision. Consecutive patients underwent bilateral cataract extraction surgery and implantation of either monofocal IOLs, monofocal IOLs using monovision, EDOF IOLs, or trifocal IOLs. Patients with preoperative biometric data, postoperative refraction, and visual acuity who completed a questionnaire regarding satisfaction and side effects were included. Visual outcome, spectacle independence, patient satisfaction, and subjective photic phenomena were assessed. Each group comprised 50 patients (100 eyes). The mean postoperative uncorrected distance, intermediate, and near visual acuities (logMAR) were: 0.17 ± 0.14 (Snellen 20/30), not applicable, and not applicable for monofocal; 0.08 ± 0.12 (Snellen 20/24), not applicable, and 0.07 ± 0.12 (Snellen 20/23) for monovision; 0.03 ± 0.08 (Snellen 20/21), 0.08 ± 0.12 (Snellen 20/24), and 0.23 ± 0.17 (Snellen 20/34) for EDOF; 0.07 ± 0.09 (Snellen 20/23), 0.08 ± 0.11 (Snellen 20/24), and 0.02 ± 0.06 (Snellen 20/21) for trifocal. Spectacle independence was reported by 36%, 70%, 74%, and 92% of patients, respectively. Postoperative halos and/or glare were experienced by 2%, 6%, 14%, and 38%, respectively, of which 2%, 0%, 6%, and 10%, respectively, were functionally disturbing. A total of 64%, 72%, 78%, and 76%, respectively, would choose the same IOL again. Patient satisfaction rates were high in all groups. Trifocal IOLs were more effective in improving unaided whole range of vision, but were associated with a higher rate of photic phenomena. The EDOF IOL and monovision provided partial spectacle independence with less photic phenomena. [J Refract Surg. 2019;35(7):434-440.].