Showing papers on "Contrast (vision) published in 2011"
TL;DR: In this article, an approach is proposed which consists in computing the ratio between the gradient of the visible edges between the image before and after contrast restoration, which is an indicator of visibility enhancement.
Abstract: The contrast of outdoor images acquired under adverse weather conditions, especially foggy weather, is altered by the scattering of daylight by atmospheric particles. As a consequence, different methods have been designed to restore the contrast of these images. However, there is a lack of methodology to assess the performances of the methods or to rate them. Unlike image quality assessment or image restoration areas, there is no easy way to have a reference image, which makes the problem not straightforward to solve. In this paper, an approach is proposed which consists in computing the ratio between the gradient of the visible edges between the image before and after contrast restoration. In this way, an indicator of visibility enhancement is provided based on the concept of visibility level, commonly used in lighting engineering. Finally, the methodology is applied to contrast enhancement assessment and to the comparison of tone-mapping operators.
555 citations
TL;DR: This is the first report of acute effects of CF on the efficiency of visual function, and can be explained by increased cerebral blood flow caused by CF, although in the case of contrast sensitivity there may be an additional contribution from CF induced retinal blood flow changes.
185 citations
TL;DR: It was showed that the cross-sectional area of retinal tissue between the plexiform layers in cystoid macular edema, as imaged by OCT, is the best indicator of visual function at baseline.
Abstract: Purpose. To determine whether the volume of retinal tissue passing between the inner and outer retina in macular edema could be used as an indicator of visual acuity.
Methods. Diabetic and uveitic patients with cystoid macular edema (81 subjects, 129 eyes) were recruited. Best corrected logMAR visual acuity and spectral optical coherence tomography (OCT/SLO; OTI, Toronto, ONT, Canada) were performed in all patients. Coronal OCT scans obtained from a cross section of the retina between the plexiform layers were analyzed with a grid of five concentric radii (500, 1000, 1500, 2000, and 2500 μm centered on the fovea). The images were analyzed to determine the amount of retinal tissue present within each ring. A linear regression model was developed to determine the relationship between tissue integrity and logMAR visual acuity.
Results. A linear relationship between tissue integrity and VA was demonstrated. The volume of retinal tissue between the plexiform layers in rings 1 and 2 (up to 1000 μm from the foveal center) predicted 80% of visual acuity. By contrast, central macular thickness within the central 1000 μm predicted only 14% of visual acuity.
Conclusions. This study showed that the cross-sectional area of retinal tissue between the plexiform layers in cystoid macular edema, as imaged by OCT, is the best indicator of visual function at baseline. Further prospective treatment trials are needed to investigate this parameter as a predictor of visual outcome after intervention.
164 citations
TL;DR: An overview of the visual problems likely to be encountered in Parkinson's disease and the pattern electroretinogram (PERG) is useful in evaluating retinal dopamine mechanisms and in monitoring dopamine therapies in PD.
Abstract: Parkinson's disease (PD) is a common disorder of middle-aged and elderly people in which degeneration of the extrapyramidal motor system causes significant movement problems. In some patients, however, there are additional disturbances in sensory systems including loss of the sense of smell and auditory and/or visual problems. This paper is a general overview of the visual problems likely to be encountered in PD. Changes in vision in PD may result from alterations in visual acuity, contrast sensitivity, colour discrimination, pupil reactivity, eye movements, motion perception, visual field sensitivity, and visual processing speeds. Slower visual processing speeds can also lead to a decline in visual perception especially for rapidly changing visual stimuli. In addition, there may be disturbances of visuospatial orientation, facial recognition problems, and chronic visual hallucinations. Some of the treatments used in PD may also have adverse ocular reactions. The pattern electroretinogram (PERG) is useful in evaluating retinal dopamine mechanisms and in monitoring dopamine therapies in PD. If visual problems are present, they can have an important effect on the quality of life of the patient, which can be improved by accurate diagnosis and where possible, correction of such defects.
136 citations
TL;DR: It is concluded that anisometropic amblyopia led to both monocular and interocular deficits, and that the properties of binocular combination were abnormal in many aspects in amblyopic vision.
Abstract: Amblyopia is a developmental disorder that results in deficits of monocular and binocular vision. It is presently unclear whether these deficits result from attenuation of signals in the amblyopic eye, inhibition by signals in the fellow eye, or both. In this study, we characterize mechanisms underlying anisometropic amblyopia using a binocular phase and contrast combination paradigm and a contrast gain control model. Subjects dichoptically viewed two slightly different images and reported the perceived contrast and phase of the resulting cyclopean percept. We found that the properties of binocular combination were abnormal in many aspects in amblyopic vision. The observed abnormalities can be explained by a combination of (1) attenuated monocular signal in the amblyopic eye, (2) stronger interocular contrast gain control from the fellow eye to the signal in the amblyopic eye (direct interocular inhibition), and (3) stronger interocular contrast gain control from the fellow eye to the contrast gain control signal from the amblyopic eye (indirect interocular inhibition). We conclude that anisometropic amblyopia led to both monocular and interocular deficits. A complete understanding of the mechanisms underlying amblyopia requires studies of both monocular deficits and binocular interactions.
102 citations
TL;DR: A release/replenishment model revealed that a single, homogeneous pool of synaptic vesicles is sufficient to generate this behavior and that a partial depletion of the RRP is the dominant mechanism for shaping the biphasic contrast/luminance response.
Abstract: Contrast is computed throughout the nervous system to encode changing inputs efficiently. The retina encodes luminance and contrast over a wide range of visual conditions and must adapt its responses to maintain sensitivity and to avoid saturation. We examined the means by which one type of adaptation allows individual synapses to compute contrast and encode luminance in biphasic responses to step changes in light levels. Light-evoked depletion of the readily releasable vesicle pool (RRP) at rod bipolar cell ribbon synapses in rat retina limited the dynamic range available to encode transient, but not sustained, responses, thereby allowing the transient and sustained components of release to compute temporal contrast and encode mean light levels, respectively. A release/replenishment model revealed that a single, homogeneous pool of synaptic vesicles is sufficient to generate this behavior and that a partial depletion of the RRP is the dominant mechanism for shaping the biphasic contrast/luminance response.
102 citations
TL;DR: The data demonstrate that instead of electrically stimulating synapses, selective behavioral changes are evoked in humans by using equivalently timed visual stimulation, suggesting that both LTD- and LTP-like protocols control human behavior but that the direction of changes is determined by the feature incorporated into the stimulation protocol.
94 citations
TL;DR: It is concluded that even modest interocular differences in refractive error can influence visual function, and the degree of anisometropia is correlated with the acuity of the weak eye.
90 citations
TL;DR: The study compared two visual illusions that alter subjective judgments of brightness: the simultaneous brightness contrast illusion, in which two circles of identical physical brightness appear different because of different surround luminance, and the Kanizsa triangle illusion, which occurs when the visual system extrapolates a surface without actual physical stimulation.
Abstract: The perception of even the most elementary features of the visual environment depends strongly on their spatial context. In the study reported here, we asked at what level of abstraction such effects require conscious processing of the context. We compared two visual illusions that alter subjective judgments of brightness: the simultaneous brightness contrast illusion, in which two circles of identical physical brightness appear different because of different surround luminance, and the Kanizsa triangle illusion, which occurs when the visual system extrapolates a surface without actual physical stimulation. We used a novel interocular masking technique that allowed us to selectively render only the context invisible. Simultaneous brightness contrast persisted even when the surround was masked from awareness. In contrast, participants did not experience illusory contours when the inducing context was masked. Our findings show that invisible context is resolvable by low-level processes involved in surface-brightness perception, but not by high-level processes that assign surface borders through perceptual completion.
83 citations
TL;DR: Visual noise with a 1/f amplitude spectrum was judged more comfortable than any image with a relative increase in contrast energy within a narrow spatial frequency band, consistent with the idea that deviation from the statistics of natural images could cause discomfort.
81 citations
TL;DR: A novel semi-fragile spatial watermarking method based on LBP operators by using the local pixel contrast for the embedding and extraction of watermarks is presented and a general framework for multi-level imageWatermarking is proposed.
TL;DR: The new‐generation multifocal IOL provided adequate distance, intermediate, and, to a lesser extent, near vision with high rates of spectacle freedom.
Abstract: Purpose To evaluate visual function after bilateral implantation of a zonal refractive aspheric multifocal intraocular lens (IOL) Setting Private practice surgery center, Valencia, Spain Design Cohort study Methods Consecutive eyes with cataract had bilateral implantation of Lentis Mplus LS-312 multifocal IOLs Distance, intermediate, and near visual acuities; contrast sensitivity; defocus curves; and a quality-of-vision questionnaire, including presence of halos or dysphotopsia, were evaluated 6 months postoperatively A control group of age-matched monofocal pseudophakic patients was included to compare contrast sensitivity function Results In the multifocal group, the mean binocular corrected distance visual acuity (logMAR) was −004 ± 007 at 6 m, 011 ± 010 at 1 m, and 006 ± 007 at 40 cm The defocus curve showed little intermediate vision drop off Photopic contrast sensitivity for distance was similar to the monofocal IOL contrast sensitivity function, while photopic contrast sensitivity for near and mesopic contrast sensitivity for distance with or without glare was reduced at high frequencies The mean patient satisfaction was 809 ± 130 (scale 0 to 10); 844% of patients were completely independent of spectacles Moderate halos, glare, and night-vision problems were reported by 62%, 125%, and 156% of patients, respectively Conclusion The new-generation multifocal IOL provided adequate distance, intermediate, and, to a lesser extent, near vision with high rates of spectacle freedom Halos occurred, and other photic phenomena should be expected in a small percentage of patients Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned
TL;DR: The authors found that rats are more likely to miss the target when flankers are collinear and the same impairment was found even when the flanker luminance was sign-reversed relative to the target.
Abstract: We measure rats' ability to detect an oriented visual target grating located between two flanking stimuli ("flankers"). Flankers varied in contrast, orientation, angular position, and sign. Rats are impaired at detecting visual targets with collinear flankers, compared to configurations where flankers differ from the target in orientation or angular position. In particular, rats are more likely to miss the target when flankers are collinear. The same impairment is found even when the flanker luminance was sign-reversed relative to the target. These findings suggest that contour alignment alters visual processing in rats, despite their lack of orientation columns in the visual cortex. This is the first report that the arrangement of visual features relative to each other affects visual behavior in rats. To provide a conceptual framework for our findings, we relate our stimuli to a contrast normalization model of early visual processing. We suggest a pattern-sensitive generalization of the model that could account for a collinear deficit. These experiments were performed using a novel method for automated high-throughput training and testing of visual behavior in rodents.
TL;DR: The results indicate that foveal CS is impaired in glaucoma despite good visual acuity, suggesting that central visual function damage occurs in glAUcoma.
Abstract: Objective To demonstrate differences in foveal constrast sensitivity (CS) between glaucomatous and nonglaucomatous eyes using a simple, rapid computerized test. Methods This study included consecutive patients with glaucoma (35 eyes) and age-matched control participants (23 eyes) with visual acuity of 20/30 or better. Patients with any other ocular disease, including cataract, were excluded. All participants underwent a comprehensive ocular examination, perimetry, and CS. Contrast sensitivity was examined by means of 2 computerized psychophysical tests. The transient method included the presentation of a target in a temporal, 2-alternative, forced-choice procedure, and the static method involved 4 forced-choice procedures. The targets were Gabor patches with spatial frequencies of 1.5 to 9.0 cycles per degree. The tests were conducted under photopic and mesopic conditions. Results Significantly lower foveal CS was found in glaucomatous eyes under photopic and mesopic conditions for all spatial frequencies ( P P P Conclusions The results indicate that foveal CS is impaired in glaucoma despite good visual acuity, suggesting that central visual function damage occurs in glaucoma. The similarity between the 2 methods of testing implies that the static method, being the shorter and easier one, may be used in future research. Further research is necessary to establish a CS testing role in the screening and monitoring of glaucoma.
TL;DR: LSI is integrated with spatial frequency domain imaging (SFDI) to suppress multiple scattering and absorption effects and provides an integrated approach for simultaneous mapping of blood flow and oxygenation and optical properties which can be used to inform tissue metabolism.
Abstract: Laser Speckle Imaging (LSI) images interference patterns produced by coherent addition of scattered laser light to map subsurface tissue perfusion. However, the effect of longer path length photons is typically unknown and poses a limitation towards absolute quantification. In this work, LSI is integrated with spatial frequency domain imaging (SFDI) to suppress multiple scattering and absorption effects. First, depth sensitive speckle contrast is shown in phantoms by separating a deep source (4 mm) from a shallow source (2 mm) of speckle contrast by using a high spatial frequency of illumination (0.24 mm−1). We develop an SFD adapted correlation diffusion model and show that with high frequency (0.24 mm−1) illumination, doubling of absorption contrast results in only a 1% change in speckle contrast versus 25% change using a planar unmodulated (0 mm−1) illumination. Similar absorption change is mimicked in vivo imaging a finger occlusion and the relative speckle contrast change from baseline is 10% at 0.26 mm−1 versus 60% at 0 mm−1 during a finger occlusion. These results underscore the importance of path length and optical properties in determining speckle contrast. They provide an integrated approach for simultaneous mapping of blood flow (speckle contrast) and oxygenation (optical properties) which can be used to inform tissue metabolism.
TL;DR: The lower addition of ReSTOR multifocal IOL resulted in a narrower defocus profile, a farther reading distance, and better intermediate visual acuity and thus increased patient satisfaction.
Abstract: Purpose To evaluate the advantages and disadvantages of the new low-addition (add) (+3.00 diopter [D]) ReSTOR multifocal IOL compared with the preceding ReSTOR model with +4.00 D add. Setting University Eye Hospital, Tuebingen, Germany. Design Comparative case series. Methods Patients with a +3.00 D or +4.00 D add multifocal IOL were examined for uncorrected and distance-corrected visual acuity at distance, intermediate, and near. A defocus profile was assessed, individual reading distance and the distance for lowest intermediate visual acuity were determined. Patient satisfaction was evaluated with a standardized questionnaire. Contrast sensitivity was tested under mesopic and photopic conditions. Results Uncorrected and distance-corrected intermediate visual acuities were statistically significantly better in the +3.00 D add group (24 eyes) than in the +4.00 D add group (30 eyes); distance and near visual acuities were not different between groups. The defocus profile significantly varied between groups. The +4.00 D add group had a closer reading distance (33.0 cm) than the +3.00 D add group (43.5 cm), a closer point of lowest intermediate visual acuity (65.8 cm versus 86.9 cm) and worse lowest intermediate visual acuity (20/59 ± 4.5 letters [SD] versus 20/48 ± 5.5 letters). Thus, patients in the +3.00 D add group reported being more satisfied with intermediate visual acuity. The +3.00 D add group reported more glare but less halos than the +4.00 D add group; contrast sensitivity was not different. Conclusion The lower addition resulted in a narrower defocus profile, a farther reading distance, and better intermediate visual acuity and thus increased patient satisfaction. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned. Additional disclosure is found in the footnotes.
Journal Article•
TL;DR: Increased cataract severity is strongly associated with a decrease in both VA and AULCSF, and contrast sensitivity scores may offer additional information over standard VA tests in patients with early age-related cataracts.
Abstract: Purpose: To determine the effect of cataract type and severity in eyes with pure types of age-related lens opacities on visual acuity (VA) and contrast sensitivity in the presence and absence of glare conditions. Methods: Sixty patients with senile cataracts aged 40 years or older with no other ocular pathologies were evaluated for VA and contrast sensitivity with and without glare. Lens opacities were classified according to the Lens Opacities Classification System (LOCS) III. VA was measured using the Snellen chart. Contrast sensitivity was measured with the Vector Vision CSV-1000E chart in the presence and absence of glare by calculating the area under log contrast sensitivity (log CS) function (AULCSF). Results: Cataracts were posterior subcapsular in 26 eyes, cortical in 19 eyes and nuclear in 15 eyes. VA significantly decreased with increasing cataract severity and there was significant loss of contrast sensitivity at all spatial frequencies with increasing cataract severity. AULCSF significantly decreased with increasing cataract severity in the presence and absence of glare conditions. Contrast sensitivity was significantly reduced at high spatial frequency (18 cpd) in cortical cataracts in the presence of glare in day light and at low spatial frequency (3 cpd) in night light. Conclusion: Increased cataract severity is strongly associated with a decrease in both VA and AULCSF. Contrast sensitivity scores may offer additional information over standard VA tests in patients with early age-related cataracts.
TL;DR: Binocular summation and inhibition are important factors in the QoL and visual experience of MS patients, and may explain why some prefer to patch or close 1 eye in the absence of diplopia or ocular misalignment.
TL;DR: It is suggested that contour alignment alters visual processing in rats, despite their lack of orientation columns in the visual cortex, in the first report that the arrangement of visual features relative to each other affects visual behavior in rats.
Abstract: We measure rats' ability to detect an oriented visual target grating located between two flanking stimuli ("flankers"). Flankers varied in contrast, orientation, angular position, and sign. Rats are impaired at detecting visual targets with collinear flankers, compared to configurations where flankers differ from the target in orientation or angular position. In particular, rats are more likely to miss the target when flankers are collinear. The same impairment is found even when the flanker luminance was sign-reversed relative to the target. These findings suggest that contour alignment alters visual processing in rats, despite their lack of orientation columns in visual cortex. This is the first report that the arrangement of visual features relative to each other affects visual behavior in rats. To provide a conceptual framework for our findings, we relate our stimuli to a contrast normalization model of early visual processing. We suggest a pattern-sensitive generalization of the model which could account for a collinear deficit. These experiments were performed using a novel method for automated high-throughput training and testing of visual behavior in rodents.
21 Jul 2011
TL;DR: The Histogram Modified Contrast Limited Adaptive Histogram Equalization (HM-CLAHE) is proposed in this paper to adjust the level of contrast enhancement, which in turn gives the resultant image a strong contrast and brings the local details for more relevant interpretation.
Abstract: Early detection of breast cancer in the mammograms is very essential in the field of medicine. Contrast enhancement for the detection of micro calcification of mammograms based on the Histogram Modified Contrast Limited Adaptive Histogram Equalization (HM-CLAHE) is presented. Histogram equalization is an effective and simple technique for contrast enhancement. The standard histogram equalization (HE) usually results in excessive contrast enhancement because of lack of control on the level of enhancement. The Histogram Modified Contrast Limited Adaptive Histogram Equalization (HM-CLAHE) is proposed in this paper to adjust the level of contrast enhancement, which in turn gives the resultant image a strong contrast and brings the local details for more relevant interpretation. It incorporates both histogram modifications as an optimization technique and Contrast Limited Adaptive Histogram Equalization. This method is tested for Mias mammogram images. The performance of this method is determined using the parameter like Enhancement Measure (EME). From the subjective and quantitative measures it is interesting that this proposed technique provides better contrast enhancement with preserving the local information of the mammogram images.
TL;DR: Visual function, most notably acuity without LVAs, is the best predictor of self-reported VRAL assessed by the Activity Inventory, and rehabilitation strategies addressing depression and adjustment could improve perceived visual disability.
Abstract: Purpose.: The use of patient-reported outcome (PRO) measures to assess self-reported difficulty in visual activities is common in patients with impaired vision. This study determines the visual and psychosocial factors influencing patients' responses to self-report measures, to aid in understanding what is being measured.
Methods.: One hundred visually impaired participants completed the Activity Inventory (AI), which assesses self-reported, vision-related activity limitation (VRAL) in the task domains of reading, mobility, visual information, and visual motor tasks. Participants also completed clinical tests of visual function (distance visual acuity and near reading performance both with and without low vision aids [LVAs], contrast sensitivity, visual fields, and depth discrimination), and questionnaires assessing depressive symptoms, social support, adjustment to visual loss, and personality.
Results.: Multiple regression analyses identified that an acuity measure (distance or near), and, to a lesser extent, near reading performance without LVAs, visual fields, and contrast sensitivity best explained self-reported VRAL (28%–50% variance explained). Significant psychosocial correlates were depression and adjustment, explaining an additional 6% to 19% unique variance. Dependent on task domain, the parameters assessed explained 59% to 71% of the variance in self-reported VRAL.
Conclusions.: Visual function, most notably acuity without LVAs, is the best predictor of self-reported VRAL assessed by the AI. Depression and adjustment to visual loss also significantly influence self-reported VRAL, largely independent of the severity of visual loss and most notably in the less vision-specific tasks. The results suggest that rehabilitation strategies addressing depression and adjustment could improve perceived visual disability.
TL;DR: It is concluded that luminance and chromatic contrast sensitivities are subject to distinct modulations at the time of saccades, resulting from independent neural processes.
Abstract: Sensitivity to luminance contrast is reduced just before and during saccades (saccadic suppression), whereas sensitivity to color contrast is unimpaired peri-saccadically and enhanced post-saccadically. The exact spatiotemporal map of these perceptual effects is as yet unknown. Here, we measured detection thresholds for briefly flashed Gaussian blobs modulated in either luminance or chromatic contrast, displayed at a range of eccentricities. Sensitivity to luminance contrast was reduced peri-saccadically by a scaling factor, which was almost constant across retinal space. Saccadic suppression followed a similar time course across all tested eccentricities and was maximal shortly after the saccade onset. Sensitivity to chromatic contrast was enhanced post-saccadically at all tested locations. The enhancement was not specifically linked to the execution of saccades, as it was also observed following a displacement of retinal images comparable to that caused by a saccade. We conclude that luminance and chromatic contrast sensitivities are subject to distinct modulations at the time of saccades, resulting from independent neural processes.
TL;DR: In this paper, a review of contrast sensitivity across different classes of vertebrates, with an emphasis on the frequency contrast sensitivity peak and visual acuity, is presented, and the power of the association between visual acience and the spatial frequency of the contrast sensitivity function peak is analyzed.
Abstract: The luminance contrast sensitivity function has been investigated using behavioral and electrophysiological methods in many vertebrate species. Some features are conserved across species as a shape of the function, but other features, such as the contrast sensitivity peak value, spatial frequency contrast sensitivity peak, and visual acuity have changed. Here, we review contrast sensitivity across different classes of vertebrates, with an emphasis on the frequency contrast sensitivity peak and visual acuity. We also correlate the data obtained from the literature to test the power of the association between visual acuity and the spatial frequency of the contrast sensitivity function peak.
TL;DR: This study aimed to investigate the prevalence of impairment of visual function amongst European drivers and found that among drivers with visual impairment, black-and-white vision impairment is more common than not.
Abstract: .
Purpose: This study aimed to investigate the prevalence of impairment of visual function amongst European drivers.
Methods: A total of 2422 drivers from five European countries underwent a battery of visual function tests, including tests for visual acuity (VA), visual field (VF), contrast sensitivity, straylight (glare sensitivity) and useful field of view (UFOV). Subjects belonged to the following age categories: 45–54 years; 55–64 years; 65–74 years, and ≥ 75 years. A group of subjects aged 20–30 years served as a reference group. Results were compared with current standards for the visual function of drivers in the EU.
Results: Visual acuity in 0.5% of the younger group and 5.3% of the eldest group was below the standard required for driving. Visual acuity after proper refraction adhered to the standard in the majority of cases. Visual field results were below standard or questionable in 2.7% and 2.4%, respectively, of subjects in the eldest group. In this eldest group, impaired contrast sensitivity was present in 6.3%, increased glare sensitivity in 29.5% and impaired UFOV in 21.6% of subjects, but, as there are no standards for these criteria, the exact level of prevalence depends on the definition of impairment.
Conclusions: Prevalences of impairment of visual functions that are not included in current standards (particularly contrast sensitivity and glare sensitivity) are much higher than prevalences of functions that are included (VA and VF).
TL;DR: The results suggest that the relative dominance in signal output of the N1 and P1 components is dependent on spatial frequency (SF) luminance contrast for simple stimuli up to natural scene imagery possessing few edges, however, such a dependency shifts to a dominant N1 signal for natural scenes possessing abundant edge content and operates independently of SF luminance Contrast.
Abstract: The contrast response function of early visual evoked potentials elicited by sinusoidal gratings is known to exhibit characteristic potentials closely associated with the processes of parvocellular and magnocellular pathways. Specifically, the N1 component has been linked with parvocellular processes, while the P1 component has been linked with magnocellular processes. However, little is known regarding the response properties of the N1 and P1 components during the processing and encoding of complex (i.e., broadband) stimuli such as natural scenes. Here, we examine how established physical characteristics of natural scene imagery modulate the N1 and P1 components in humans by providing a systematic investigation of component modulation as visual stimuli are gradually built up from simple sinusoidal gratings to highly complex natural scene imagery. The results suggest that the relative dominance in signal output of the N1 and P1 components is dependent on spatial frequency (SF) luminance contrast for simple stimuli up to natural scene imagery possessing few edges. However, such a dependency shifts to a dominant N1 signal for natural scenes possessing abundant edge content and operates independently of SF luminance contrast.
TL;DR: The development of a standardized dynamic visual acuity test is needed as are well-controlled scientific studies to evaluate the benefits of sports vision training.
Abstract: UNLABELLED : The building blocks of effective sports vision are visual acuity and contrast sensitivity. Proper measurement of these spatial vision attributes is necessary for repeatability in the clinic or in the laboratory. The most repeatable method of testing visual acuity is with logMAR charts-either the Bailey-Lovie chart or the Early Treatment Diabetic Retinopathy Study chart. The Pelli-Robson and the Mars are the most repeatable contrast sensitivity tests. Athletes may or may not demonstrate superior visual acuity and contrast sensitivity compared with age-matched nonathlete populations, and the optical quality of their eyes may be similar. Dynamic visual acuity in athletes and their performance are typically superior to those of nonathletes. How these differences relate to on-field performance is not known. Other changes to the visual system because of refractive surgery or contact lens wear may increase higher order aberrations and reduce low-contrast visual acuity. The ability to improve already-normal visual acuity is unclear although contrast sensitivity can improve with fast-paced video games. Tinted contact lenses help reduce discomfort glare and speed up adaptation but do not have an appreciable effect on visual acuity and contrast sensitivity. CONCLUSION The use of valid and repeatable visual acuity and contrast sensitivity tests is essential for measuring the differences in visual performance among athletes and nonathletes. The development of a standardized dynamic visual acuity test is needed as are well-controlled scientific studies to evaluate the benefits of sports vision training.
TL;DR: A recently established test designed to quantify the degree of suppression in amblyopia to participants with normal binocular vision found that mismatches in mean luminance between the two eyes had a pronounced effect on the balance point determination.
Abstract: PURPOSE To better understand the neural basis of sensory dominance in the normal population, we applied a recently established test designed to quantify the degree of suppression in amblyopia to participants with normal binocular vision. METHODS This test quantifies the degree of dichoptic imbalance in coherent motion sensitivity by manipulating the contrast of stimuli seen by the two eyes. The contrast at which balanced dichoptic motion sensitivity occurs is referred to as the "balance point" and is an estimate of the degree of suppression. We apply the same logic to the measurement of sensory dominance by measuring the distribution of "balance points" within the normal population. RESULTS We show that although most subjects are balanced or only weakly imbalanced, a minority is strongly imbalanced. To ascertain the site of sensory dominance, we assessed the degree to which normal sensory balance can be modulated by changing the interocular mean luminance. We found that mismatches in mean luminance between the two eyes had a pronounced effect on the balance point determination. CONCLUSIONS Because cells in the lateral geniculate nucleus exhibit a strong modulation to sustained changes in the mean light level, this may suggests that the inhibitory circuits underlying sensory eye dominance are located at a precortical site.
TL;DR: In normal foveal vision and anisometropic amblyopia, the effects of flankers largely reflects a reduction in visibility and may be explained by masking, while in peripheral vision and strabismicAmblyopic vision, the results show clearly that theeffects of flanks depend on both the task and the type of visual system.
Abstract: Using identical stimuli and methods, we assessed the effects of flankers on three different tasks, orientation discrimination, contrast discrimination, and detection, in central, peripheral, and amblyopic vision. The goal was to understand the factors that limit performance of a task in the presence of flankers in each of these visual systems. The results demonstrate that: (1) For unflanked targets, the losses in peripheral and amblyopic vision (relative to the normal fovea) are ordered, with the loss of unflanked contrast discrimination thresholds considerably smaller than those for either detection or orientation discrimination. (2) For flanked targets, in normal foveal vision and anisometropic amblyopia, the critical distance is more or less proportional to the target size, whereas in peripheral and strabismic amblyopic vision, the critical distance shows much less (or no) dependence on target size. (3) For the normal fovea, and anisometropic amblyopia, when the target is large (>≈0.2 deg) the amount of threshold elevation induced by flankers is low, increasing when the target is very small. On the other hand, for the periphery and the amblyopic eyes of most strabismic amblyopes, the elevation is large over the range of sizes tested. (4) In peripheral and strabismic amblyopic vision, remote flankers elevate orientation discrimination and contrast discrimination thresholds but not detection thresholds. Our results show clearly that the effects of flanks depend on both the task and the type of visual system. We conclude that in normal foveal vision and anisometropic amblyopia, the effects of flankers largely reflects a reduction in visibility and may be explained by masking. On the other hand, in peripheral vision and strabismic amblyopia, the effects of flankers on orientation discrimination and to a lesser extent contrast discrimination cannot be explained by simple masking and are due to crowding.