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Yassin M, Lev M, Polat U. Space, time, and dynamics of binocular interactions. Sci Rep 2023; 13:21449. [PMID: 38052879 DOI: 10.1038/s41598-023-48380-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Accepted: 11/25/2023] [Indexed: 12/07/2023] Open
Abstract
Binocular summation (BS), defined as the superiority of binocular over monocular visual performance, shows that thresholds are about 40% (a factor of 1.4) better in binocular than in monocular viewing. However, it was reported that different amounts of BS exist in a range from 1.4 to 2 values because BS is affected by the spatiotemporal parameters of the stimulus. Lateral interactions can be defined as the neuron's ability to affect the neighboring neurons by either inhibiting or exciting their activity. We investigated the effect of the spatial and temporal domains on binocular interactions and BS under the lateral masking paradigm and how BS would be affected by lateral interactions via a lateral masking experiment. The two temporal alternative forced-choice (2TAFC) method was used. The stimuli consisted of a central vertically oriented Gabor target and high-contrast Gabor flankers positioned in two configurations (orthogonal or collinear) with target-flanker separations of either 2 or 3 wavelengths (λ), presented at 4 different presentation times (40, 80, 120, and 200 ms) using a different order of measurements across the different experiments. Opaque lenses were used to control the monocular and binocular vision. BS is absent at close distances (2λ), depending on the presentation time's order, for the collinear but not for the orthogonal configuration. However, BS exists at more distant flankers (collinear and orthogonal, 3λ). BS is not uniform (1.4); it depends on the stimulus condition, the presentation times, the order, and the method that was used to control the monocular and binocular vision.
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Affiliation(s)
- Marzouk Yassin
- School of Optometry and Vision Sciences, Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
| | - Maria Lev
- School of Optometry and Vision Sciences, Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
| | - Uri Polat
- School of Optometry and Vision Sciences, Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel.
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Benhaim-Sitbon L, Lev M, Polat U. Abnormal basic visual processing functions in binocular fusion disorders. Sci Rep 2023; 13:19301. [PMID: 37935803 PMCID: PMC10630403 DOI: 10.1038/s41598-023-46291-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Accepted: 10/30/2023] [Indexed: 11/09/2023] Open
Abstract
Heterophoria is a common type of binocular fusion disorder that consists of a latent eye misalignment with potential consequences on daily activities such as reading or working on a computer (with CVS). Crowding, a type of contextual modulation, can also impair reading. Our recent studies found an abnormal pattern of low-level visual processing with larger perceptive fields (PF) in heterophoria. The PF is the fundamental processing unit of human vision and both masking and crowding depend on its size. We investigated how heterophoria would impact the PF's size via a lateral masking experiment and consequently affect the foveal crowding at different letter-spacings (the crowding zone). More specifically, we explored the relationship between crowding, lateral masking, the PF's size, and the amount of heterophoria. The binocular horizontal PF's size was larger with heterophoric subjects, in agreement with our previous study. We found a stronger crowding and an extended crowding zone associated with slower response times; this shows that the processing of letter identification under both crowded and uncrowded conditions requires more processing effort in heterophoric individuals. In agreement with previous studies, we found a correlation between the crowding zone and the PF's size; each was strongly correlated with the amount of phoria. These findings resemble those involving the PF size and the extended crowding found at the fovea in amblyopia and young children. We suggest that these findings could help explain the inter-observers' variability found in the masking literature, and the reading difficulties often encountered in subjects with high heterophoria.
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Affiliation(s)
- Laura Benhaim-Sitbon
- School of Optometry and Vision Sciences, Faculty of Life Sciences, Bar-Ilan University, Ramat Gan, Israel
| | - Maria Lev
- School of Optometry and Vision Sciences, Faculty of Life Sciences, Bar-Ilan University, Ramat Gan, Israel
| | - Uri Polat
- School of Optometry and Vision Sciences, Faculty of Life Sciences, Bar-Ilan University, Ramat Gan, Israel.
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Benhaim-Sitbon L, Lev M, Polat U. Extended perceptive field revealed in humans with binocular fusion disorders. Sci Rep 2023; 13:6584. [PMID: 37085571 PMCID: PMC10121568 DOI: 10.1038/s41598-023-33429-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Accepted: 04/12/2023] [Indexed: 04/23/2023] Open
Abstract
Binocular vision disorders or dysfunctions have considerable impact on daily visual activities such as reading. Heterophoria (phoria) is a latent eye misalignment (with a prevalence of up to 35%) that appears in conditions that disrupt binocular vision and it may affect the quality of binocular fusion. Our recent study, which used lateral masking (LM), suggests that subjects with binocular fusion disorders (horizontal phoria) exhibit an asymmetry and an abnormal pattern of both binocular and monocular lateral interactions, but only for the horizontal meridian (HM). The perceptive field (PF) is the fundamental processing unit of human vision and both masking and crowding depend on its size. An increased PF size is found in amblyopic populations or in young children. We hypothesized that the PF's size would be asymmetric only for the phoric group (larger along the HM). We estimated the PF's size using two different methods (LM with equal-phase and opposite-phase flankers). Phoric subjects exhibited a larger binocular PF size, only for the HM, confirming our hypothesis of an asymmetric PF size. However, the monocular PF size of phoric and control subjects was similar. Phoria affects the PF's size similarly to meridional amblyopia but without being attributed to abnormal refraction. We suggest that these findings could help explain the inter-observer variability found in the masking literature and the reading difficulties often encountered in subjects with high heterophoria. Since perceptual learning can reduce the PF's size, further investigation of training may provide a novel therapy to reduce some symptoms related to heterophoria.
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Affiliation(s)
- Laura Benhaim-Sitbon
- School of Optometry and Vision Sciences, Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
| | - Maria Lev
- School of Optometry and Vision Sciences, Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
| | - Uri Polat
- School of Optometry and Vision Sciences, Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel.
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Abstract
Stereopsis provides us with a vivid impression of the depth and distance of objects in our 3- dimensional world. Stereopsis is important for a number of everyday visual tasks, including (but not limited to) reaching and grasping, fine visuo-motor control, and navigating in our world. This review briefly discusses the neural substrate for normal binocular vision and stereopsis and its development in primates; outlines some of the issues and limitations of stereopsis tests and examines some of the factors that limit the typical development of stereopsis and the causes and consequences of stereo-deficiency and stereo-blindness. Finally, we review several approaches to improving or recovering stereopsis in both neurotypical individuals and those with stereo-deficiency and stereo-blindness and outline some emerging strategies for improving stereopsis.
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Min SH, Chen Y, Jiang N, He Z, Zhou J, Hess RF. Issues Revisited: Shifts in Binocular Balance Depend on the Deprivation Duration in Normal and Amblyopic Adults. Ophthalmol Ther 2022; 11:2027-2044. [PMID: 36008603 DOI: 10.1007/s40123-022-00560-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Accepted: 08/03/2022] [Indexed: 10/15/2022] Open
Abstract
INTRODUCTION Recent studies indicate that short-term monocular deprivation increases the deprived eye's contribution to binocular fusion in both adults with normal vision and amblyopia. In this study, we investigated whether the changes in visual plasticity depended on the duration of deprivation in normal and amblyopic adults. METHODS Twelve anisometropia amblyopic observers (aged 24.8 ± 2.3 years) and 12 age-matched normal observers (aged 23.9 ± 1.2 years) participated in the study. The non-dominant eye of normal observers or amblyopic eye of amblyopic observers was deprived for 30, 120, and 300 min in a randomized order. Their eye balance was measured with a phase combination task, which is a psychophysical test, before and after the deprivation. This design enabled us to measure changes induced in binocular balance as an index visual plasticity due to monocular deprivations. RESULTS By comparing the ocular dominance changes as a result of monocular deprivation with different deprivation durations, we found evidence that the ocular dominance changes are slightly larger after longer deprivations in both normal and amblyopic observers, albeit with a statistical significance. The changes from 120-min were significantly greater than those from 30-min deprivation in both groups. The magnitude of changes in sensory eye balance was significantly larger in normal observers than that in the amblyopic observers; however, the longevity of changes in visual plasticity was found to be more long-lasting in amblyopic observers than the normal counterparts. CONCLUSIONS The duration of deprivation matters in both normal and amblyopic observers. Ocular dominance imbalance that is typically observed in amblyopia can be more ameliorated with a longer duration of deprivation.
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Affiliation(s)
- Seung Hyun Min
- School of Ophthalmology and Optometry, Affiliated Eye Hospital, State Key Laboratory of Ophthalmology, Optometry and Vision Science, Wenzhou Medical University, Wenzhou, Zhejiang, China.,McGill Vision Research, Department of Ophthalmology and Visual Sciences, McGill University, Montreal, Canada
| | - Yiya Chen
- School of Ophthalmology and Optometry, Affiliated Eye Hospital, State Key Laboratory of Ophthalmology, Optometry and Vision Science, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Nan Jiang
- School of Ophthalmology and Optometry, Affiliated Eye Hospital, State Key Laboratory of Ophthalmology, Optometry and Vision Science, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Zhifen He
- School of Ophthalmology and Optometry, Affiliated Eye Hospital, State Key Laboratory of Ophthalmology, Optometry and Vision Science, Wenzhou Medical University, Wenzhou, Zhejiang, China.
| | - Jiawei Zhou
- School of Ophthalmology and Optometry, Affiliated Eye Hospital, State Key Laboratory of Ophthalmology, Optometry and Vision Science, Wenzhou Medical University, Wenzhou, Zhejiang, China.
| | - Robert F Hess
- McGill Vision Research, Department of Ophthalmology and Visual Sciences, McGill University, Montreal, Canada
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Min SH, Mao Y, Chen S, Hess RF, Zhou J. Modulation of mean luminance improves binocular balance across spatial frequencies in amblyopia. iScience 2022; 25:104598. [PMID: 35789838 PMCID: PMC9249912 DOI: 10.1016/j.isci.2022.104598] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Revised: 05/06/2022] [Accepted: 06/08/2022] [Indexed: 11/30/2022] Open
Abstract
Amblyopia is a visual impairment that perturbs binocular balance at high spatial frequencies in favor of the fellow eye. Studies reveal that amblyopes who had been treated with monocular therapies still show imbalance. Binocular balance is achieved when both eyes’ inputs are weighed equally. A reduced light can diminish the dimmed eye's weight in binocular combination. In this study, we examined if binocular balance across spatial frequencies could be improved by reducing the luminance of the fellow eye in adult amblyopes. By doing so, we relieved their binocular imbalance across spatial frequencies. Also, normal observers showed amblyopic binocular imbalance when the dominant eye’s light level was dimmed. Therefore, reducing the luminance in the unaffected eye in amblyopia mitigated the binocular imbalance, whereas doing so in normal adults simulated the amblyopic imbalance across spatial frequencies. Binocular balance is impaired in amblyopia Reduced luminance of the fellow eye can improve it across spatial frequencies in amblyopia Reduced luminance of one eye from normal observers simulates amblyopic imbalance
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Affiliation(s)
- Seung Hyun Min
- School of Ophthalmology and Optometry, Affiliated Eye Hospital, State Key Laboratory of Ophthalmology, Optometry and Vision Science, Wenzhou Medical University, Wenzhou, Zhejiang, China
- McGill Vision Research, Department of Ophthalmology and Visual Sciences, McGill University, Montreal, QC, Canada
| | - Yu Mao
- School of Ophthalmology and Optometry, Affiliated Eye Hospital, State Key Laboratory of Ophthalmology, Optometry and Vision Science, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Shijia Chen
- School of Ophthalmology and Optometry, Affiliated Eye Hospital, State Key Laboratory of Ophthalmology, Optometry and Vision Science, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Robert F. Hess
- McGill Vision Research, Department of Ophthalmology and Visual Sciences, McGill University, Montreal, QC, Canada
| | - Jiawei Zhou
- School of Ophthalmology and Optometry, Affiliated Eye Hospital, State Key Laboratory of Ophthalmology, Optometry and Vision Science, Wenzhou Medical University, Wenzhou, Zhejiang, China
- Corresponding author
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Min SH, Mao Y, Chen S, He Z, Hess RF, Zhou J. A clinically convenient test to measure binocular balance across spatial frequency in amblyopia. iScience 2022; 25:103652. [PMID: 35024586 PMCID: PMC8733258 DOI: 10.1016/j.isci.2021.103652] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Revised: 10/25/2021] [Accepted: 12/13/2021] [Indexed: 11/29/2022] Open
Abstract
Amblyopia is a visual disorder that originates from the brain. It exhibits no pathology in the eye. Studies have shown that measuring both visual acuity and binocular balance for assessing amblyopia could be more helpful. However, tests that measure binocular balance are time-consuming, often exceeding 30 min. Their long test durations prevent them from being used in the clinic. For this reason, we have developed a quick (i.e., about 7 min) and precise tool that quantitatively measures binocular balance of patients with amblyopia. The new test can capture binocular imbalance that is typically exhibited at high spatial frequency in amblyopes. In addition, it has an excellent test-retest reliability and repeatability between two experimental sessions. We hope that our newly developed test can pave the road for physicians and researchers to better assess and diagnose amblyopia and other visual disorders that disrupt binocular balance beyond the laboratory. Measuring binocular balance of amblyopes is difficult and time-consuming (>30 min) We introduce a psychophysical test that is reliable and quick (7 min)
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Affiliation(s)
- Seung Hyun Min
- School of Ophthalmology and Optometry, Affiliated Eye Hospital, State Key Laboratory of Ophthalmology, Optometry and Vision Science, Wenzhou Medical University, Wenzhou, Zhejiang, China.,McGill Vision Research, Department of Ophthalmology and Visual Sciences, McGill University, Montreal, Canada
| | - Yu Mao
- School of Ophthalmology and Optometry, Affiliated Eye Hospital, State Key Laboratory of Ophthalmology, Optometry and Vision Science, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Shijia Chen
- School of Ophthalmology and Optometry, Affiliated Eye Hospital, State Key Laboratory of Ophthalmology, Optometry and Vision Science, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Zhifen He
- School of Ophthalmology and Optometry, Affiliated Eye Hospital, State Key Laboratory of Ophthalmology, Optometry and Vision Science, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Robert F Hess
- McGill Vision Research, Department of Ophthalmology and Visual Sciences, McGill University, Montreal, Canada
| | - Jiawei Zhou
- School of Ophthalmology and Optometry, Affiliated Eye Hospital, State Key Laboratory of Ophthalmology, Optometry and Vision Science, Wenzhou Medical University, Wenzhou, Zhejiang, China
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Excitatory Contribution to Binocular Interactions in Human Visual Cortex Is Reduced in Strabismic Amblyopia. J Neurosci 2021; 41:8632-8643. [PMID: 34433631 PMCID: PMC8513700 DOI: 10.1523/jneurosci.0268-21.2021] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 08/12/2021] [Accepted: 08/13/2021] [Indexed: 01/14/2023] Open
Abstract
Binocular summation in strabismic amblyopia is typically reported as being absent or greatly reduced in behavioral studies and is thought to be because of a preferential loss of excitatory interactions between the eyes. Here, we studied how excitatory and suppressive interactions contribute to binocular contrast interactions along the visual cortical hierarchy of humans with strabismic and anisometropic amblyopia in both sexes, using source-imaged steady-state visual evoked potentials (SSVEP) over a wide range of relative contrast between the two eyes. Dichoptic parallel grating stimuli modulated at unique temporal frequencies in each eye allowed us to quantify spectral response components associated with monocular inputs (self-terms) and the response components because of interaction of the inputs of the two eyes [intermodulation (IM) terms]. Although anisometropic amblyopes revealed a similar pattern of responses to normal-vision observers, strabismic amblyopes exhibited substantially reduced IM responses across cortical regions of interest (V1, V3a, hV4, hMT+ and lateral occipital cortex), indicating reduced interocular interactions in visual cortex. A contrast gain control model that simultaneously fits self- and IM-term responses within each cortical area revealed different patterns of binocular interactions between individuals with normal and disrupted binocularity. Our model fits show that in strabismic amblyopia, the excitatory contribution to binocular interactions is significantly reduced in both V1 and extra-striate cortex, whereas suppressive contributions remain intact. Our results provide robust electrophysiological evidence supporting the view that disruption of binocular interactions in strabismus or amblyopia is because of preferential loss of excitatory interactions between the eyes.SIGNIFICANCE STATEMENT We studied how excitatory and suppressive interactions contribute to binocular contrast interactions along the visual cortical hierarchy of humans with normal and amblyopic vision, using source-imaged SSVEP and frequency-domain analysis of dichoptic stimuli over a wide range of relative contrast between the two eyes. A dichoptic contrast gain control model was used to characterize these interactions in amblyopia and provided a quantitative comparison to normal vision. Our model fits revealed different patterns of binocular interactions between normal and amblyopic vision. Strabismic amblyopia significantly reduced excitatory contributions to binocular interactions, whereas suppressive contributions remained intact. Our results provide robust evidence supporting the view that the preferential loss of excitatory interactions disrupts binocular interactions in strabismic amblyopia.
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Chow A, Silva AE, Tsang K, Ng G, Ho C, Thompson B. Binocular Integration of Perceptually Suppressed Visual Information in Amblyopia. Invest Ophthalmol Vis Sci 2021; 62:11. [PMID: 34515731 PMCID: PMC8444466 DOI: 10.1167/iovs.62.12.11] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Accepted: 08/20/2021] [Indexed: 01/01/2023] Open
Abstract
Purpose The purpose of this study was to assess whether motion information from suppressed amblyopic eyes can influence visual perception. Methods Participants with normal vision (n = 20) and with amblyopia (n = 20; 11 anisometropic and 9 strabismic/mixed) viewed dichoptic, orthogonal drifting gratings through a mirror stereoscope. Participants continuously reported form and motion percepts as gratings rivaled for 60 seconds. Responses were binned into categories ranging from binocular integration to complete suppression. Periods when the grating presented to the nondominant/amblyopic eye was suppressed were analyzed further to determine the extent of binocular integration of motion. Results Individuals with amblyopia experienced longer periods of non-preferred eye suppression than controls. When the non-preferred eye grating was suppressed, binocular integration of motion occurred 48.1 ± 6.2% and 31.2 ± 5.8% of the time in control and amblyopic participants, respectively. Periods of motion integration from the suppressed eye were significantly non-zero for both groups. Conclusions Visual information seen only by a suppressed amblyopic eye can be binocularly integrated and influence the overall visual percept. These findings reveal that visual information subjected to interocular suppression can still contribute to binocular vision and suggest the use of appropriate optical correction for the amblyopic eye to improve image quality for binocular combination.
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Affiliation(s)
- Amy Chow
- Department of Optometry and Vision Science, University of Waterloo, Waterloo, Ontario, Canada
| | - Andrew E. Silva
- Department of Optometry and Vision Science, University of Waterloo, Waterloo, Ontario, Canada
| | - Katelyn Tsang
- Department of Optometry and Vision Science, University of Waterloo, Waterloo, Ontario, Canada
| | - Gabriel Ng
- Mount Pleasant Optometry Centre, Vancouver, British Columbia, Canada
| | - Cindy Ho
- Mount Pleasant Optometry Centre, Vancouver, British Columbia, Canada
| | - Benjamin Thompson
- Department of Optometry and Vision Science, University of Waterloo, Waterloo, Ontario, Canada
- Center for Eye and Vision Research, 17W Science Park, Hong Kong
- Liggins Institute, University of Auckland, Auckland, New Zealand
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10
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Levi DM. Amblyopia. HANDBOOK OF CLINICAL NEUROLOGY 2021; 178:13-30. [PMID: 33832673 DOI: 10.1016/b978-0-12-821377-3.00002-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Amblyopia is a neurodevelopmental abnormality that results in physiological alterations in the visual pathways and impaired vision in one eye, less commonly in both. It reflects a broad range of neural, perceptual, oculomotor, and clinical abnormalities that can occur when normal visual development is disrupted early in life. Aside from refractive error, amblyopia is the most common cause of vision loss in infants and young children. It causes a constellation of perceptual deficits in the vision of the amblyopic eye, including a loss of visual acuity, position acuity, and contrast sensitivity, particularly at high spatial frequencies, as well as increased internal noise and prolonged manual and saccadic reaction times. There are also perceptual deficits in the strong eye, such as certain types of motion perception, reflecting altered neural responses and functional connectivity in visual cortex (Ho et al., 2005). Treatment in young children consists of correction of any refractive error and patching of the strong eye. Compliance with patching is challenging and a substantial proportion of amblyopic children fail to achieve normal acuity or stereopsis even after extended periods of treatment. There are a number of promising experimental treatments that may improve compliance and outcomes, such as the playing of action video games with the strong eye patched. Although there may be a sensitive period for optimal effects of treatment, there is evidence that amblyopic adults may still show some benefit of treatment. However, there is as yet no consensus on the treatment of adults with amblyopia.
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Affiliation(s)
- Dennis M Levi
- School of Optometry & Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, CA, United States.
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11
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Abstract
Recent work has transformed our ideas about the neural mechanisms, behavioral consequences and effective therapies for amblyopia. Since the 1700's, the clinical treatment for amblyopia has consisted of patching or penalizing the strong eye, to force the "lazy" amblyopic eye, to work. This treatment has generally been limited to infants and young children during a sensitive period of development. Over the last 20 years we have learned much about the nature and neural mechanisms underlying the loss of spatial and binocular vision in amblyopia, and that a degree of neural plasticity persists well beyond the sensitive period. Importantly, the last decade has seen a resurgence of research into new approaches to the treatment of amblyopia both in children and adults, which emphasize that monocular therapies may not be the most effective for the fundamentally binocular disorder that is amblyopia. These approaches include perceptual learning, video game play and binocular methods aimed at reducing inhibition of the amblyopic eye by the strong fellow eye, and enhancing binocular fusion and stereopsis. This review focuses on the what we've learned over the past 20 years or so, and will highlight both the successes of these new treatment approaches in labs around the world, and their failures in clinical trials. Reconciling these results raises important new questions that may help to focus future directions.
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Affiliation(s)
- Dennis M Levi
- University of California, Berkeley, School of Optometry & Helen Wills Neuroscience Institute, Berkeley, CA, USA.
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12
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Barboni MTS, Maneschg OA, Németh J, Nagy ZZ, Vidnyánszky Z, Bankó ÉM. Dichoptic Spatial Contrast Sensitivity Reflects Binocular Balance in Normal and Stereoanomalous Subjects. Invest Ophthalmol Vis Sci 2020; 61:23. [PMID: 32931571 PMCID: PMC7500129 DOI: 10.1167/iovs.61.11.23] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Accepted: 08/17/2020] [Indexed: 01/27/2023] Open
Abstract
Purpose To study binocular balance by comparing dichoptic and standard monocular contrast sensitivity function (CSF) in stereonormal and stereoanomalous/stereoblind amblyopic subjects. Methods Sixteen amblyopes and 17 controls participated. Using the capability of the passive three-dimensional display, we measured their CSF both monocularly and dichoptically at spatial frequencies 0.5, 1, 2, 4, and 8 cpds using achromatic Gabor patches on a luminance noise background. During monocular stimulation, the untested eye was covered, while for the dichoptic stimulation the untested eye viewed background noise. Dichoptic CSF of both eyes was acquired within one block. Results In patients with central fixation, dichoptic viewing had a large negative impact on the CSF of the amblyopic eye, although it hardly affected that of the dominant eye. In contrast, dichoptic viewing had a small but significant effect on both eyes for controls. In addition, all participants lay along a continuum in terms of how much their two eyes were affected by dichoptic stimulation: by using two predefined contrast sensitivity ratios, namely, amblyopic sensitivity decrement and dichoptic sensitivity decrement, not only did we find a significant correlation between these variables among all participants, but also the two groups were identified with minimum error using a cluster analysis. Conclusions Dichoptic CSF may be considered to measure visual performance in patients with altered binocular vision, because it better reflects the visual capacity of the amblyopic eye than the standard monocular examinations. It may also be a more reliable parameter to assess the efficacy of modern approaches to treat amblyopia.
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Affiliation(s)
| | - Otto Alexander Maneschg
- Department of Ophthalmology, Semmelweis University, Budapest, Hungary
- Bionic Innovation Center, Budapest, Hungary
| | - János Németh
- Department of Ophthalmology, Semmelweis University, Budapest, Hungary
- Bionic Innovation Center, Budapest, Hungary
| | - Zoltán Zsolt Nagy
- Department of Ophthalmology, Semmelweis University, Budapest, Hungary
| | - Zoltán Vidnyánszky
- Brain Imaging Centre, Research Centre for Natural Sciences, Budapest, Hungary
| | - Éva M. Bankó
- Brain Imaging Centre, Research Centre for Natural Sciences, Budapest, Hungary
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Elfadaly D, Abdelrazik ST, Thomas PBM, Dekker TM, Dahlmann-Noor A, Jones PR. Can Psychophysics Be Fun? Exploring the Feasibility of a Gamified Contrast Sensitivity Function Measure in Amblyopic Children Aged 4-9 Years. Front Med (Lausanne) 2020; 7:469. [PMID: 32984366 PMCID: PMC7480072 DOI: 10.3389/fmed.2020.00469] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Accepted: 07/13/2020] [Indexed: 12/04/2022] Open
Abstract
Routine assessments of the Contrast Sensitivity Function [CSF] could be useful for the diagnosis and monitoring of amblyopia. However, current CSF measures are not clinically practical, as they are too slow, too boring, and too uncomfortable to sustain a young child's interest. Here we assess the feasibility of a more gamified approach to CSF testing, in which a maximum likelihood psychophysical algorithm (QUEST+) is combined with a largely unconstrained user interface (no fixation target, head restraints, or discrete trials). Twenty-five amblyopes (strabismic, anisometropic, or mixed) aged 4.0–9.2 years performed the gamified CSF assessment monocularly (once per eye). The test required the child to “pop” (press) grating stimuli as they “bounced” around a tablet screen. Head tracking via the tablet's front-facing camera was used to adjust for variations in viewing distance post hoc. CSFs were fitted for each eye, and Area Under the CSF (AUCSF) computed as a summary measure of sensitivity. The results showed that AUCSF measurements were able to separate moderately and severely amblyopic eyes from fellow eyes (case-control effect), and to distinguish individuals with varying degrees of vision loss (dose effect). Even the youngest children exhibited no difficulties completing the test or comprehending what to do, and most children appeared to find the test genuinely enjoyable. Informal feedback from a focus group of older children was also positive, although potential shortcomings with the present design were identified. This feasibility study indicates that gamified, child-friendly vision assessments have promise as a future means of pediatric clinical assessment. Such measures could be particularly valuable for assessing children outside of conventional eye-care facilities (e.g., home-monitoring, school screening).
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Affiliation(s)
- Doaa Elfadaly
- Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom.,Department of Ophthalmology, Faculty of Medicine, Minia University, Minia, Egypt
| | | | - Peter B M Thomas
- Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom.,NIHR Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom
| | - Tessa M Dekker
- Child Vision Laboratory, Institute of Ophthalmology, University College London (UCL), London, United Kingdom
| | - Annegret Dahlmann-Noor
- Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom.,NIHR Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom
| | - Pete R Jones
- NIHR Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom.,Child Vision Laboratory, Institute of Ophthalmology, University College London (UCL), London, United Kingdom.,Division of Optometry and Visual Sciences, City, University of London, London, United Kingdom
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14
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Moshkovitz A, Lev M, Polat U. Monocular and Binocular Temporal Visual Perception of Infantile Nystagmus. Sci Rep 2020; 10:4946. [PMID: 32188906 PMCID: PMC7080729 DOI: 10.1038/s41598-020-61914-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Accepted: 02/26/2020] [Indexed: 11/24/2022] Open
Abstract
Contrast sensitivity is mostly used as a tool for testing aspects of visual functions. Infantile nystagmus is a pathological phenomenon that affects the spatial-temporal visual functions due to spontaneous oscillating movements of the eyes. We examined the spatial-temporal aspects of nystagmus perception, aiming to investigate the mechanisms underlying the deterioration of their visual performance. We tested the monocular and binocular contrast sensitivity of nystagmus and normally sighted subjects by measuring contrast detection of a Gabor target with spatial frequencies slightly above the cutoff threshold of each subject (nystagmus ~3; controls = 9cpd; presentation times 60–480 ms). The dominant eye of nystagmus revealed large differences over the non-dominant eye, highlighting the superiority of the dominant over the non-dominant eye in nystagmus. In addition, binocular summation mechanism was impaired in majority of the nystagmus subjects. Furthermore, these differences are not attributed to differences in visual acuity. Moreover, the visual performance in nystagmus continue to improve for longer presentation time compared with controls and was longer in the poor eye. Since the results are not due to differences in eye movements and strabismus, we suggest that the differences are due to developmental impairment in the visual system during the critical period.
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Affiliation(s)
- Avital Moshkovitz
- School of Optometry and Vision Sciences, Faculty of Life Sciences, Bar-Ilan University, Ramat Gan, Israel
| | - Maria Lev
- School of Optometry and Vision Sciences, Faculty of Life Sciences, Bar-Ilan University, Ramat Gan, Israel
| | - Uri Polat
- School of Optometry and Vision Sciences, Faculty of Life Sciences, Bar-Ilan University, Ramat Gan, Israel.
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15
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Beylerian M, Hess RF, Matonti F, Denis D, Chavane F, Reynaud A. Interocular suppressive interactions in amblyopia depend on spatial frequency. Vision Res 2020; 168:18-28. [PMID: 32044586 DOI: 10.1016/j.visres.2019.11.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Revised: 08/30/2019] [Accepted: 11/21/2019] [Indexed: 11/27/2022]
Abstract
In amblyopia, there is an interocular suppressive imbalance that results in the fixing eye dominating perception. In this study, we aimed to determine whether these suppressive interactions were narrowband and tuned for spatial frequency or broadband and independent of spatial frequency. We measured the contrast sensitivity and masking functions of fifteen amblyopic subjects and seventeen control subjects using the quick Contrast Sensitivity Function (qCSF) approach (Lesmes, Lu, Baek, & Albright, 2010). We first measured the monocular sensitivity functions of each participant and thereafter corrected for it. We then measured masking sensitivity functions for low, mid and high spatial frequency masks, normalized to their visibility. In the control group, we observed that the strength of dichoptic masking is equivalent between the two eyes. It is also tuned such that masking by low spatial frequencies in one eye mainly affects low spatial frequencies in the other eye and masking by high spatial frequencies mainly affects high spatial frequencies. In amblyopes, although the interocular masking is also tuned for spatial frequency, it is not equivalent between the two eyes: the masking effect from the amblyopic to fixing eye is weaker than the other way around. The asymmetry observed in the strength of masking between the two eyes in amblyopia is tuned for spatial frequency. It is not the consequence of the contrast sensitivity deficit of the amblyopic eye nor is it the consequence of abnormally strong masking from the fixing eye. Rather it is due to an abnormally weak masking strength by the amblyopic eye per se.
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Affiliation(s)
- Marie Beylerian
- Department of Ophthalmology, CHU NORD, Marseille, France; Institut de Neurosciences de la Timone (INT), Centre National de la Recherche Scientifique (CNRS) and Aix-Marseille Université (AMU), Marseille, France
| | - Robert F Hess
- McGill Vision Research, Department of Ophthalmology and Visual Sciences, McGill University, Montreal, Quebec, Canada
| | - Frédéric Matonti
- Institut de Neurosciences de la Timone (INT), Centre National de la Recherche Scientifique (CNRS) and Aix-Marseille Université (AMU), Marseille, France; Centre Paradis Monticelli, Marseille, France
| | - Danièle Denis
- Department of Ophthalmology, CHU NORD, Marseille, France; Institut de Neurosciences de la Timone (INT), Centre National de la Recherche Scientifique (CNRS) and Aix-Marseille Université (AMU), Marseille, France
| | - Frédéric Chavane
- Institut de Neurosciences de la Timone (INT), Centre National de la Recherche Scientifique (CNRS) and Aix-Marseille Université (AMU), Marseille, France
| | - Alexandre Reynaud
- McGill Vision Research, Department of Ophthalmology and Visual Sciences, McGill University, Montreal, Quebec, Canada.
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16
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Abstract
Anisometropic amblyopia is unilateral by definition and current treatment recommendations reflect that characteristic. However, recent research suggests a binocular component that deserves consideration. The aim of this review is to consider the levels of anisometropia deemed amblyogenic, and the cortical changes that occur in the presence of anisometropic amblyopia. Particular attention is given to cortical changes that impact the binocularity of these individuals. Knowledge of binocular deficits in anisometropic amblyopia has implications for current, accepted treatment regimens which are monocular in nature. Therefore, the integrity of binocular function in anisometropic amblyopia and its impact on the visual outcome will be evaluated. Given the rise in binocular treatments under clinical trial for amblyopia, this review also aims to evaluate the evidence of potentially enhanced benefits to anisometropic amblyopes from proposed new binocular therapies.
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Affiliation(s)
| | - Charlotte J Codina
- Academic Unit of Ophthalmology and Orthoptics, Faculty of Medicine, Dentistry and Health, University of Sheffield, Sheffield, UK
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17
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Dorr M, Kwon M, Lesmes LA, Miller A, Kazlas M, Chan K, Hunter DG, Lu ZL, Bex PJ. Binocular Summation and Suppression of Contrast Sensitivity in Strabismus, Fusion and Amblyopia. Front Hum Neurosci 2019; 13:234. [PMID: 31354452 PMCID: PMC6640006 DOI: 10.3389/fnhum.2019.00234] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Accepted: 06/25/2019] [Indexed: 11/13/2022] Open
Abstract
Purpose: Amblyopia and strabismus affect 2%–5% of the population and cause a broad range of visual deficits. The response to treatment is generally assessed using visual acuity, which is an insensitive measure of visual function and may, therefore, underestimate binocular vision gains in these patients. On the other hand, the contrast sensitivity function (CSF) generally takes longer to assess than visual acuity, but it is better correlated with improvement in a range of visual tasks and, notably, with improvements in binocular vision. The present study aims to assess monocular and binocular CSFs in amblyopia and strabismus patients. Methods: Both monocular CSFs and the binocular CSF were assessed for subjects with amblyopia (n = 11), strabismus without amblyopia (n = 20), and normally sighted controls (n = 24) using a tablet-based implementation of the quick CSF, which can assess a full CSF in <3 min. Binocular summation was evaluated against a baseline model of simple probability summation. Results: The CSF of amblyopic eyes was impaired at mid-to-high spatial frequencies compared to fellow eyes, strabismic eyes without amblyopia, and control eyes. Binocular contrast summation exceeded probability summation in controls, but not in subjects with amblyopia (with or without strabismus) or strabismus without amblyopia who were able to fuse at the test distance. Binocular summation was less than probability summation in strabismic subjects who were unable to fuse. Conclusions: We conclude that monocular and binocular contrast sensitivity deficits define important characteristics of amblyopia and strabismus that are not captured by visual acuity alone and can be measured efficiently using the quick CSF.
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Affiliation(s)
- Michael Dorr
- Department of Electrical and Computer Engineering, Technical University Munich, Munich, Germany
| | - MiYoung Kwon
- Department of Ophthalmology, School of Medicine, University of Alabama at Birmingham, Birmingham, AL, United States
| | | | - Alexandra Miller
- College of Medicine and Health, University of Exeter, Exeter, United Kingdom
| | - Melanie Kazlas
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical School, Boston, MA, United States.,Department of Ophthalmology, Harvard Medical School, Boston, MA, United States
| | - Kimberley Chan
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical School, Boston, MA, United States.,Department of Ophthalmology, Harvard Medical School, Boston, MA, United States
| | - David G Hunter
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical School, Boston, MA, United States.,Department of Ophthalmology, Harvard Medical School, Boston, MA, United States
| | - Zhong-Lin Lu
- Department of Psychology, The Ohio State University, Columbus, OH, United States
| | - Peter J Bex
- Department of Psychology, Northeastern University, Boston, MA, United States
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18
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Baker DH, Lygo FA, Meese TS, Georgeson MA. Binocular summation revisited: Beyond √2. Psychol Bull 2018; 144:1186-1199. [PMID: 30102058 PMCID: PMC6195301 DOI: 10.1037/bul0000163] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Revised: 05/10/2018] [Accepted: 05/11/2018] [Indexed: 12/02/2022]
Abstract
Our ability to detect faint images is better with two eyes than with one, but how great is this improvement? A meta-analysis of 65 studies published across more than 5 decades shows definitively that psychophysical binocular summation (the ratio of binocular to monocular contrast sensitivity) is significantly greater than the canonical value of √2. Several methodological factors were also found to affect summation estimates. Binocular summation was significantly affected by both the spatial and temporal frequency of the stimulus, and stimulus speed (the ratio of temporal to spatial frequency) systematically predicts summation levels, with slow speeds (high spatial and low temporal frequencies) producing the strongest summation. We furthermore show that empirical summation estimates are affected by the ratio of monocular sensitivities, which varies across individuals, and is abnormal in visual disorders such as amblyopia. A simple modeling framework is presented to interpret the results of summation experiments. In combination with the empirical results, this model suggests that there is no single value for binocular summation, but instead that summation ratios depend on methodological factors that influence the strength of a nonlinearity occurring early in the visual pathway, before binocular combination of signals. Best practice methodological guidelines are proposed for obtaining accurate estimates of neural summation in future studies, including those involving patient groups with impaired binocular vision. (PsycINFO Database Record (c) 2018 APA, all rights reserved).
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19
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The mechanism of short-term monocular deprivation is not simple: separate effects on parallel and cross-oriented dichoptic masking. Sci Rep 2018; 8:6191. [PMID: 29670145 PMCID: PMC5906446 DOI: 10.1038/s41598-018-24584-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Accepted: 04/04/2018] [Indexed: 11/11/2022] Open
Abstract
Short-term deprivation of the input to one eye increases the strength of its influence on visual perception. This effect was first demonstrated using a binocular rivalry task. Incompatible stimuli are shown to the two eyes, and their competition for perceptual dominance is then measured. Further studies used a combination task, which measures the contribution of each eye to a fused percept. Both tasks show an effect of deprivation, but there have been inconsistencies between them. This suggests that the deprivation causes multiple effects. We used dichoptic masking to explore this possibility. We measured the contrast threshold for detecting a grating stimulus presented to the target eye. Thresholds were elevated when a parallel or cross-oriented grating mask was presented to the other eye. This masking effect was reduced by depriving the target eye for 150 minutes. We tested fourteen subjects with normal vision, and found individual differences in the magnitude of this reduction. Comparing the reduction found in each subject between the two masks (parallel vs. cross-oriented), we found no correlation. This indicates that there is not a single underlying effect of short-term monocular deprivation. Instead there are separate effects which can have different dependencies, and be probed by different tasks.
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20
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Chang MY, Demer JL, Isenberg SJ, Velez FG, Pineles SL. Decreased Binocular Summation in Strabismic Amblyopes and Effect of Strabismus Surgery. Strabismus 2017; 25:73-80. [PMID: 28463606 DOI: 10.1080/09273972.2017.1318153] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
PURPOSE Binocular summation (BiS) occurs when binocular visual function surpasses that of the better eye alone. We sought to evaluate whether strabismic amblyopia reduces BiS more than strabismus alone, and determine whether BiS improves in strabismic amblyopes after strabismus surgery. METHODS We prospectively recruited 15 patients with strabismic amblyopia who then underwent strabismus surgery. Thirty age-matched normal subjects and 30 non-amblyopic strabismic patients served as controls. Subjects underwent binocular and monocular visual acuity testing on high-contrast Early Treatment Diabetic Retinopathy Study (ETDRS) as well as 2.5% and 1.25% Sloan low contrast acuity (LCA) charts. BiS was calculated as the difference between better eye and binocular scores. RESULTS Strabismic amblyopes and strabismic controls did not significantly differ in preoperative BiS, but both had subnormal BiS preoperatively on LCA charts. Among 11 strabismic amblyopes with preoperative and postoperative BiS measurements, average postoperative BiS was not significantly different from preoperative. Improved LCA BiS postoperatively occurred in some patients and was associated with measurable preoperative stereoacuity (P=0.02), older age at strabismus onset (P=0.02), and larger preoperative angle of strabismus (P=0.0043). CONCLUSIONS In this preliminary study, strabismic amblyopes experienced subnormal BiS, but amblyopia generally did not further impair BiS beyond that due to strabismus alone. Some strabismic amblyopes experienced improved low-contrast BiS after strabismus surgery. This suggests that further investigation in larger groups of patients should be undertaken to analyze a previously unrecognized functional benefit of strabismus surgery in strabismic amblyopes.
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Affiliation(s)
- Melinda Y Chang
- a Department of Ophthalmology , Stein Eye Institute, UCLA Medical Center , Los Angeles , CA
| | - Joseph L Demer
- a Department of Ophthalmology , Stein Eye Institute, UCLA Medical Center , Los Angeles , CA.,d Department of Neurology, and Neuroscience and Bioengineering Interdepartmental Programs , University of California , Los Angeles , CA
| | - Sherwin J Isenberg
- a Department of Ophthalmology , Stein Eye Institute, UCLA Medical Center , Los Angeles , CA
| | - Federico G Velez
- a Department of Ophthalmology , Stein Eye Institute, UCLA Medical Center , Los Angeles , CA.,b Doheny Eye Institute, UCLA , Los Angeles , CA.,c Olive View-UCLA Medical Center , Los Angeles , CA
| | - Stacy L Pineles
- a Department of Ophthalmology , Stein Eye Institute, UCLA Medical Center , Los Angeles , CA
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21
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Kehrein S, Kohnen T, Fronius M. Dynamics of Interocular Suppression in Amblyopic Children during Electronically Monitored Occlusion Therapy: First Insight. Strabismus 2016; 24:51-62. [PMID: 27220458 DOI: 10.3109/09273972.2016.1170047] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
PURPOSE Interocular suppression is assumed to be the mechanism leading to impaired visual acuity, especially in strabismic amblyopia. Little is known about the dynamics of suppression during treatment. The aim of our study was to assess the development of the depth of suppression and its relation to changes in visual acuity during electronically monitored occlusion treatment. METHODS In a prospective pilot study, 15 amblyopes (8 with and 7 without strabismus) aged 5 to 16 years (mean 10.24 years) were examined before initiation of patching and then every 3 to 6 weeks for 4 months. To quantify suppression, a red filter ladder (Sbisa bar) was used, attenuating the image of the dominant eye until the patients reported a binocular perception (diplopia, rivalry, color mixture) or a change in eye dominance. Acuity was assessed with crowded Landolt rings. Daily occlusion was recorded using occlusion dose monitors. RESULTS The depth of interocular suppression showed a biphasic change: it increased significantly during the first month (P=0.02), while visual acuity improved (mean 0.14 log units ±0.13; P<0.01). During the following 3 months, median suppression decreased back to the initial values. This reduction in suppression was more pronounced in anisometropic patients without strabismus than in amblyopes with strabismus. The average visual acuity steadily improved (P<0.01) during the 4 months of treatment. Mean recorded patching dose rate was 3.91 h/d. The correlation between mean daily occlusion and suppression changes was not statistically significant. CONCLUSIONS This first insight into the functional changes during electronically monitored patching suggests a complex relationship between visual acuity and interocular suppression that seems to be influenced by the presence of strabismus. Knowledge of the dynamics of interocular suppression is crucial for enhancing the outcome of occlusion treatment and also for the evaluation of its future role compared to emerging dichoptic treatments.
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Affiliation(s)
- Stephan Kehrein
- a Department of Ophthalmology , Goethe University Hospital , Frankfurt am Main , Germany
| | - Thomas Kohnen
- a Department of Ophthalmology , Goethe University Hospital , Frankfurt am Main , Germany
| | - Maria Fronius
- a Department of Ophthalmology , Goethe University Hospital , Frankfurt am Main , Germany
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22
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Orientation tuning of binocular summation: a comparison of colour to achromatic contrast. Sci Rep 2016; 6:25692. [PMID: 27168119 PMCID: PMC4863369 DOI: 10.1038/srep25692] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Accepted: 04/21/2016] [Indexed: 11/29/2022] Open
Abstract
A key function of the primary visual cortex is to combine the input from the two eyes into a unified binocular percept. At low, near threshold, contrasts a process of summation occurs if the visual inputs from the two eyes are similar. Here we measure the orientation tuning of binocular summation for chromatic and equivalent achromatic contrast. We derive estimates of orientation tuning by measuring binocular summation as a function of the orientation difference between two sinusoidal gratings presented dichoptically to different eyes. We then use a model to estimate the orientation bandwidth of the neural detectors underlying the binocular combination. We find that orientation bandwidths are similar for chromatic and achromatic stimuli at both low (0.375 c/deg) and mid (1.5 c/deg) spatial frequencies, with an overall average of 29 ± 3 degs (HWHH, s.e.m). This effect occurs despite the overall greater binocular summation found for the low spatial frequency chromatic stimuli. These results suggest that similar, oriented processes underlie both chromatic and achromatic binocular contrast combination. The non-oriented detection process found in colour vision at low spatial frequencies under monocular viewing is not evident at the binocular combination stage.
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23
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Kwon M, Wiecek E, Dakin SC, Bex PJ. Spatial-frequency dependent binocular imbalance in amblyopia. Sci Rep 2015; 5:17181. [PMID: 26603125 PMCID: PMC4658600 DOI: 10.1038/srep17181] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 10/27/2015] [Indexed: 11/30/2022] Open
Abstract
While amblyopia involves both binocular imbalance and deficits in processing high spatial frequency information, little is known about the spatial-frequency dependence of binocular imbalance. Here we examined binocular imbalance as a function of spatial frequency in amblyopia using a novel computer-based method. Binocular imbalance at four spatial frequencies was measured with a novel dichoptic letter chart in individuals with amblyopia, or normal vision. Our dichoptic letter chart was composed of band-pass filtered letters arranged in a layout similar to the ETDRS acuity chart. A different chart was presented to each eye of the observer via stereo-shutter glasses. The relative contrast of the corresponding letter in each eye was adjusted by a computer staircase to determine a binocular Balance Point at which the observer reports the letter presented to either eye with equal probability. Amblyopes showed pronounced binocular imbalance across all spatial frequencies, with greater imbalance at high compared to low spatial frequencies (an average increase of 19%, p < 0.01). Good test-retest reliability of the method was demonstrated by the Bland-Altman plot. Our findings suggest that spatial-frequency dependent binocular imbalance may be useful for diagnosing amblyopia and as an outcome measure for recovery of binocular vision following therapy.
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Affiliation(s)
- MiYoung Kwon
- Department of Ophthalmology, School of Medicine, University of Alabama at Birmingham, Birmingham, AL
| | - Emily Wiecek
- Department of Psychology, Northeastern University, Boston, MA
- New England College of Optometry, Boston, MA
| | - Steven C. Dakin
- UCL Institute of Ophthalmology, University College London, UK
- School of Optometry and Vision Science, University of Auckland, New Zealand
| | - Peter J. Bex
- Department of Psychology, Northeastern University, Boston, MA
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24
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Levi DM, Knill DC, Bavelier D. Stereopsis and amblyopia: A mini-review. Vision Res 2015; 114:17-30. [PMID: 25637854 PMCID: PMC4519435 DOI: 10.1016/j.visres.2015.01.002] [Citation(s) in RCA: 224] [Impact Index Per Article: 24.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Revised: 11/26/2014] [Accepted: 01/09/2015] [Indexed: 12/28/2022]
Abstract
Amblyopia is a neuro-developmental disorder of the visual cortex that arises from abnormal visual experience early in life. Amblyopia is clinically important because it is a major cause of vision loss in infants and young children. Amblyopia is also of basic interest because it reflects the neural impairment that occurs when normal visual development is disrupted. Amblyopia provides an ideal model for understanding when and how brain plasticity may be harnessed for recovery of function. Over the past two decades there has been a rekindling of interest in developing more effective methods for treating amblyopia, and for extending the treatment beyond the critical period, as exemplified by new clinical trials and new basic research studies. The focus of this review is on stereopsis and its potential for recovery. Impaired stereoscopic depth perception is the most common deficit associated with amblyopia under ordinary (binocular) viewing conditions (Webber & Wood, 2005). Our review of the extant literature suggests that this impairment may have a substantial impact on visuomotor tasks, difficulties in playing sports in children and locomoting safely in older adults. Furthermore, impaired stereopsis may also limit career options for amblyopes. Finally, stereopsis is more impacted in strabismic than in anisometropic amblyopia. Our review of the various approaches to treating amblyopia (patching, perceptual learning, videogames) suggests that there are several promising new approaches to recovering stereopsis in both anisometropic and strabismic amblyopes. However, recovery of stereoacuity may require more active treatment in strabismic than in anisometropic amblyopia. Individuals with strabismic amblyopia have a very low probability of improvement with monocular training; however they fare better with dichoptic training than with monocular training, and even better with direct stereo training.
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Affiliation(s)
- Dennis M Levi
- School of Optometry, Graduate Group in Vision Science and Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA 94720-2020, USA.
| | - David C Knill
- Department of Brain & Cognitive Sciences, University of Rochester, Rochester, NY 14627-0268, USA; Center for Visual Science, University of Rochester, Rochester, NY 14627-0268, USA
| | - Daphne Bavelier
- Department of Brain & Cognitive Sciences, University of Rochester, Rochester, NY 14627-0268, USA; Center for Visual Science, University of Rochester, Rochester, NY 14627-0268, USA; Psychology and Education Sciences (FPSE), University of Geneva, Geneva, Switzerland
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25
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Vedamurthy I, Nahum M, Bavelier D, Levi DM. Mechanisms of recovery of visual function in adult amblyopia through a tailored action video game. Sci Rep 2015; 5:8482. [PMID: 25719537 PMCID: PMC4894407 DOI: 10.1038/srep08482] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Accepted: 12/24/2014] [Indexed: 11/09/2022] Open
Abstract
Amblyopia is a deficit in vision that arises from abnormal visual experience early in life. It was long thought to develop into a permanent deficit, unless properly treated before the end of the sensitive period for visual recovery. However, a number of studies now suggest that adults with long-standing amblyopia may at least partially recover visual acuity and stereopsis following perceptual training. Eliminating or reducing interocular suppression has been hypothesized to be at the root of these changes. Here we show that playing a novel dichoptic video game indeed results in reduced suppression, improved visual acuity and, in some cases, improved stereopsis. Our relatively large cohort of adults with amblyopia, allowed us, for the first time, to assess the link between visual function recovery and reduction in suppression. Surprisingly, no significant correlation was found between decreased suppression and improved visual function. This finding challenges the prevailing view and suggests that while dichoptic training improves visual acuity and stereopsis in adult amblyopia, reduced suppression is unlikely to be at the root of visual recovery. These results are discussed in the context of their implication on recovery of amblyopia in adults.
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Affiliation(s)
- Indu Vedamurthy
- Department of Brain &Cognitive Sciences, University of Rochester. Rochester, New York 14627-0268, U.S.A
| | - Mor Nahum
- School of Optometry, Graduate Group in Vision Science and Helen Wills Neuroscience Institute, University of California, Berkeley. Berkeley, California, 94720-2020
| | - Daphne Bavelier
- 1] Department of Brain &Cognitive Sciences, University of Rochester. Rochester, New York 14627-0268, U.S.A [2] Faculty of Psychology and Education Sciences, University of Geneva, Switzerland
| | - Dennis M Levi
- School of Optometry, Graduate Group in Vision Science and Helen Wills Neuroscience Institute, University of California, Berkeley. Berkeley, California, 94720-2020
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26
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Hess RF, Thompson B, Baker DH. Binocular vision in amblyopia: structure, suppression and plasticity. Ophthalmic Physiol Opt 2014; 34:146-62. [PMID: 24588532 DOI: 10.1111/opo.12123] [Citation(s) in RCA: 118] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Accepted: 01/17/2014] [Indexed: 02/04/2023]
Abstract
The amblyopic visual system was once considered to be structurally monocular. However, it now evident that the capacity for binocular vision is present in many observers with amblyopia. This has led to new techniques for quantifying suppression that have provided insights into the relationship between suppression and the monocular and binocular visual deficits experienced by amblyopes. Furthermore, new treatments are emerging that directly target suppressive interactions within the visual cortex and, on the basis of initial data, appear to improve both binocular and monocular visual function, even in adults with amblyopia. The aim of this review is to provide an overview of recent studies that have investigated the structure, measurement and treatment of binocular vision in observers with strabismic, anisometropic and mixed amblyopia.
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Affiliation(s)
- Robert F Hess
- Department of Ophthalmology, McGill Vision Research, McGill University, Montreal, Canada
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27
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Kwon M, Lu ZL, Miller A, Kazlas M, Hunter DG, Bex PJ. Assessing binocular interaction in amblyopia and its clinical feasibility. PLoS One 2014; 9:e100156. [PMID: 24959842 PMCID: PMC4069064 DOI: 10.1371/journal.pone.0100156] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Accepted: 05/22/2014] [Indexed: 11/19/2022] Open
Abstract
PURPOSE To measure binocular interaction in amblyopes using a rapid and patient-friendly computer-based method, and to test the feasibility of the assessment in the clinic. METHODS Binocular interaction was assessed in subjects with strabismic amblyopia (n = 7), anisometropic amblyopia (n = 6), strabismus without amblyopia (n = 15) and normal vision (n = 40). Binocular interaction was measured with a dichoptic phase matching task in which subjects matched the position of a binocular probe to the cyclopean perceived phase of a dichoptic pair of gratings whose contrast ratios were systematically varied. The resulting effective contrast ratio of the weak eye was taken as an indicator of interocular imbalance. Testing was performed in an ophthalmology clinic under 8 mins. We examined the relationships between our binocular interaction measure and standard clinical measures indicating abnormal binocularity such as interocular acuity difference and stereoacuity. The test-retest reliability of the testing method was also evaluated. RESULTS Compared to normally-sighted controls, amblyopes exhibited significantly reduced effective contrast (∼20%) of the weak eye, suggesting a higher contrast requirement for the amblyopic eye compared to the fellow eye. We found that the effective contrast ratio of the weak eye covaried with standard clincal measures of binocular vision. Our results showed that there was a high correlation between the 1st and 2nd measurements (r = 0.94, p<0.001) but without any significant bias between the two. CONCLUSIONS Our findings demonstrate that abnormal binocular interaction can be reliably captured by measuring the effective contrast ratio of the weak eye and quantitative assessment of binocular interaction is a quick and simple test that can be performed in the clinic. We believe that reliable and timely assessment of deficits in a binocular interaction may improve detection and treatment of amblyopia.
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Affiliation(s)
- MiYoung Kwon
- Schepens Eye Research Institute/Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, United States of America
- Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Zhong-Lin Lu
- Department of Psychology, Ohio State University, Columbus, Ohio, United States of America
| | - Alexandra Miller
- Schepens Eye Research Institute/Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, United States of America
- Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Melanie Kazlas
- Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States of America
- Department of Ophthalmology, Boston Children's Hospital, Boston, Massachusetts, United States of America
| | - David G. Hunter
- Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States of America
- Department of Ophthalmology, Boston Children's Hospital, Boston, Massachusetts, United States of America
| | - Peter J. Bex
- Schepens Eye Research Institute/Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, United States of America
- Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States of America
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Xi J, Jia WL, Feng LX, Lu ZL, Huang CB. Perceptual learning improves stereoacuity in amblyopia. Invest Ophthalmol Vis Sci 2014; 55:2384-91. [PMID: 24508791 PMCID: PMC3989086 DOI: 10.1167/iovs.13-12627] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Accepted: 01/23/2014] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Amblyopia is a developmental disorder that results in both monocular and binocular deficits. Although traditional treatment in clinical practice (i.e., refractive correction, or occlusion by patching and penalization of the fellow eye) is effective in restoring monocular visual acuity, there is little information on how binocular function, especially stereopsis, responds to traditional amblyopia treatment. We aim to evaluate the effects of perceptual learning on stereopsis in observers with amblyopia in the current study. METHODS Eleven observers (21.1 ± 5.1 years, six females) with anisometropic or ametropic amblyopia were trained to judge depth in 10 to 13 sessions. Red-green glasses were used to present three different texture anaglyphs with different disparities but a fixed exposure duration. Stereoacuity was assessed with the Fly Stereo Acuity Test and visual acuity was assessed with the Chinese Tumbling E Chart before and after training. RESULTS Averaged across observers, training significantly reduced disparity threshold from 776.7″ to 490.4″ (P < 0.01) and improved stereoacuity from 200.3″ to 81.6″ (P < 0.01). Interestingly, visual acuity also significantly improved from 0.44 to 0.35 logMAR (approximately 0.9 lines, P < 0.05) in the amblyopic eye after training. Moreover, the learning effects in two of the three retested observers were largely retained over a 5-month period. CONCLUSIONS Perceptual learning is effective in improving stereo vision in observers with amblyopia. These results, together with previous evidence, suggest that structured monocular and binocular training might be necessary to fully recover degraded visual functions in amblyopia. Chinese Abstract.
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Affiliation(s)
- Jie Xi
- Key Laboratory of Behavioral Science, Institute of Psychology, Chinese Academy of Sciences, Beijing, China
| | - Wu-Li Jia
- Key Laboratory of Behavioral Science, Institute of Psychology, Chinese Academy of Sciences, Beijing, China
| | - Li-Xia Feng
- Department of Ophthalmology, First Affiliated Hospital, Anhui Medical University, Hefei, Anhui, China
| | - Zhong-Lin Lu
- Laboratory of Brain Processes, Department of Psychology, The Ohio State University, Columbus, Ohio, United States
| | - Chang-Bing Huang
- Key Laboratory of Behavioral Science, Institute of Psychology, Chinese Academy of Sciences, Beijing, China
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Ding J, Klein SA, Levi DM. Binocular combination in abnormal binocular vision. J Vis 2013; 13:14. [PMID: 23397039 PMCID: PMC4521338 DOI: 10.1167/13.2.14] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Accepted: 12/20/2012] [Indexed: 11/24/2022] Open
Abstract
We investigated suprathreshold binocular combination in humans with abnormal binocular visual experience early in life. In the first experiment we presented the two eyes with equal but opposite phase shifted sine waves and measured the perceived phase of the cyclopean sine wave. Normal observers have balanced vision between the two eyes when the two eyes' images have equal contrast (i.e., both eyes contribute equally to the perceived image and perceived phase = 0°). However, in observers with strabismus and/or amblyopia, balanced vision requires a higher contrast image in the nondominant eye (NDE) than the dominant eye (DE). This asymmetry between the two eyes is larger than predicted from the contrast sensitivities or monocular perceived contrast of the two eyes and is dependent on contrast and spatial frequency: more asymmetric with higher contrast and/or spatial frequency. Our results also revealed a surprising NDE-to-DE enhancement in some of our abnormal observers. This enhancement is not evident in normal vision because it is normally masked by interocular suppression. However, in these abnormal observers the NDE-to-DE suppression was weak or absent. In the second experiment, we used the identical stimuli to measure the perceived contrast of a cyclopean grating by matching the binocular combined contrast to a standard contrast presented to the DE. These measures provide strong constraints for model fitting. We found asymmetric interocular interactions in binocular contrast perception, which was dependent on both contrast and spatial frequency in the same way as in phase perception. By introducing asymmetric parameters to the modified Ding-Sperling model including interocular contrast gain enhancement, we succeeded in accounting for both binocular combined phase and contrast simultaneously. Adding binocular contrast gain control to the modified Ding-Sperling model enabled us to predict the results of dichoptic and binocular contrast discrimination experiments and provides new insights into the mechanisms of abnormal binocular vision.
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Affiliation(s)
- Jian Ding
- School of Optometry and the Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, California, USA
| | - Stanley A. Klein
- School of Optometry and the Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, California, USA
| | - Dennis M. Levi
- School of Optometry and the Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, California, USA
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Baker DH, Meese TS. Interocular transfer of spatial adaptation is weak at low spatial frequencies. Vision Res 2012; 63:81-7. [PMID: 22588117 DOI: 10.1016/j.visres.2012.05.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2011] [Revised: 04/16/2012] [Accepted: 05/04/2012] [Indexed: 10/28/2022]
Abstract
Adapting one eye to a high contrast grating reduces sensitivity to similar target gratings shown to the same eye, and also to those shown to the opposite eye. According to the textbook account, interocular transfer (IOT) of adaptation is around 60% of the within-eye effect. However, most previous studies on this were limited to using high spatial frequencies, sustained presentation, and criterion-dependent methods for assessing threshold. Here, we measure IOT across a wide range of spatiotemporal frequencies, using a criterion-free 2AFC method. We find little or no IOT at low spatial frequencies, consistent with other recent observations. At higher spatial frequencies, IOT was present, but weaker than previously reported (around 35%, on average, at 8c/deg). Across all conditions, monocular adaptation raised thresholds by around a factor of 2, and observers showed normal binocular summation, demonstrating that they were not binocularly compromised. These findings prompt a reassessment of our understanding of the binocular architecture implied by interocular adaptation. In particular, the output of monocular channels may be available to perceptual decision making at low spatial frequencies.
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Affiliation(s)
- Daniel H Baker
- School of Life & Health Sciences, Aston University, Birmingham B4 7ET, UK.
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31
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Voges N, Bach M, Kommerell G. Parallactic movement beats binocularity in the presence of external visual noise. Ophthalmic Physiol Opt 2012; 32:308-16. [DOI: 10.1111/j.1475-1313.2012.00917.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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32
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Design and validation of a method for evaluation of interocular interaction. Optom Vis Sci 2011; 89:183-96. [PMID: 22157978 DOI: 10.1097/opx.0b013e31823ee04a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022] Open
Abstract
PURPOSE To design a simple viewing system allowing dichoptic masking, and to validate this system in adults and children with normal vision. METHODS A Trial Frame Apparatus (TFA) was designed to evaluate interocular interaction. This device consists of a trial frame, a 1 mm pinhole in front of the tested eye and a full or partial occluder in front of the non-tested eye. The difference in visual function in one eye between the full- and partial-occlusion conditions was termed the Interaction Index. In experiment 1, low-contrast acuity was measured in six adults using five types of partial occluder. Interaction Index was compared between these five, and the occluder showing the highest Index was used in experiment 2. In experiment 2, low-contrast acuity, contrast sensitivity, and alignment sensitivity were measured in the non-dominant eye of 45 subjects (15 older adults, 15 young adults, and 15 children), using the TFA and an existing well-validated device (shutter goggles) with full and partial occlusion of the dominant eye. These measurements were repeated on 11 subjects of each group using TFA in the partial-occlusion condition only. Repeatability of visual function measurements using TFA was assessed using the Bland-Altman method and agreement between TFA and goggles in terms of visual functions and interactions was assessed using the Bland-Altman method and t-test. RESULTS In all three subject groups, the TFA showed a high level of repeatability in all visual function measurements. Contrast sensitivity was significantly poorer when measured using TFA than using goggles (p < 0.05). However, Interaction Index of all three visual functions showed acceptable agreement between TFA and goggles (p > 0.05). CONCLUSIONS The TFA may provide an acceptable method for the study of some forms of dichoptic masking in populations where more complex devices (e.g., shutter goggles) cannot be used.
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Thompson B, Richard A, Churan J, Hess RF, Aaen-Stockdale C, Pack CC. Impaired spatial and binocular summation for motion direction discrimination in strabismic amblyopia. Vision Res 2011; 51:577-84. [PMID: 21300079 DOI: 10.1016/j.visres.2011.02.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2010] [Revised: 02/01/2011] [Accepted: 02/01/2011] [Indexed: 10/18/2022]
Abstract
Amblyopia is characterised by visual deficits in both spatial vision and motion perception. While the spatial deficits are thought to result from deficient processing at both low and higher level stages of visual processing, the deficits in motion perception appear to result primarily from deficits involving higher level processing. Specifically, it has been argued that the motion deficit in amblyopia occurs when local motion information is pooled spatially and that this process is abnormally susceptible to the presence of noise elements in the stimulus. Here we investigated motion direction discrimination for abruptly presented two-frame Gabor stimuli in a group of five strabismic amblyopes and five control observers. Motion direction discrimination for this stimulus is inherently noisy and relies on the signal/noise processing of motion detectors. We varied viewing condition (monocular vs. binocular), stimulus size (5.3-18.5°) and stimulus contrast (high vs. low) in order to assess the effects of binocular summation, spatial summation and contrast on task performance. No differences were found for the high contrast stimuli; however the low contrast stimuli revealed differences between the control and amblyopic groups and between fellow fixing and amblyopic eyes. Control participants exhibited pronounced binocular summation for this task (on average a factor of 3.7), whereas amblyopes showed no such effect. In addition, the spatial summation that occurred for control eyes and the fellow eye of amblyopes was significantly attenuated for the amblyopic eyes relative to fellow eyes. Our results support the hypothesis that pooling of local motion information from amblyopic eyes is abnormal and highly sensitive to noise.
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Affiliation(s)
- Benjamin Thompson
- Department of Optometry and Vision Science, University of Auckland, New Zealand.
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34
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Niechwiej-Szwedo E, Goltz HC, Chandrakumar M, Hirji ZA, Wong AMF. Effects of anisometropic amblyopia on visuomotor behavior, I: saccadic eye movements. Invest Ophthalmol Vis Sci 2010; 51:6348-54. [PMID: 20671288 PMCID: PMC5142839 DOI: 10.1167/iovs.10-5882] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Impairment of spatiotemporal visual processing is the hallmark of amblyopia, but its effects on eye movements during visuomotor tasks have rarely been studied. Here the authors investigate how visual deficits in anisometropic amblyopia affect saccadic eye movements. METHODS Thirteen patients with anisometropic amblyopia and 13 control subjects participated. Participants executed saccades and manual reaching movements to a target presented randomly 5° or 10° to the left or right of fixation in three viewing conditions: binocular, amblyopic, and fellow eye viewing. Latency, amplitude, and peak velocity of primary and corrective saccades were measured. RESULTS Initiation of primary saccades was delayed and more variable when patients viewed monocularly with their amblyopic eye. During binocular viewing, saccadic latency exhibited increased variability and no binocular advantage in patients (i.e., mean latency was similar to that during fellow eye viewing). Mean amplitude and peak velocity of primary saccades were comparable between patients and control subjects; however, patients exhibited greater variability in saccade amplitude. The frequency of corrective saccades was greater when patients viewed with their fellow eye than it was with binocular or amblyopic eye viewing. Latency, amplitude, and peak velocity of corrective saccades in patients were normal in all viewing conditions. CONCLUSIONS Saccades had longer latency and decreased precision in amblyopia. Once saccades were initiated, however, the dynamics of saccades were not altered. These findings suggest that amblyopia is associated with slower visual processing in the afferent (sensory) pathway rather than a deficit in the efferent (motor) pathway of the saccadic system.
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Affiliation(s)
- Ewa Niechwiej-Szwedo
- Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Herbert C. Goltz
- Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Ophthalmology and Vision Sciences, University of Toronto, Toronto, Ontario, Canada
| | | | - Zahra A. Hirji
- Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Agnes M. F. Wong
- Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Ophthalmology and Vision Sciences, University of Toronto, Toronto, Ontario, Canada
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35
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Advantage of binocularity in the presence of external visual noise. Graefes Arch Clin Exp Ophthalmol 2010; 248:535-41. [DOI: 10.1007/s00417-010-1304-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2009] [Revised: 01/08/2010] [Accepted: 01/11/2010] [Indexed: 10/19/2022] Open
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Woods RL, Apfelbaum HL, Peli E. DLP-based dichoptic vision test system. JOURNAL OF BIOMEDICAL OPTICS 2010; 15:016011. [PMID: 20210457 PMCID: PMC2839799 DOI: 10.1117/1.3292015] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2009] [Revised: 11/23/2009] [Accepted: 11/24/2009] [Indexed: 05/28/2023]
Abstract
It can be useful to present a different image to each of the two eyes while they cooperatively view the world. Such dichoptic presentation can occur in investigations of stereoscopic and binocular vision (e.g., strabismus, amblyopia) and vision rehabilitation in clinical and research settings. Various techniques have been used to construct dichoptic displays. The most common and most flexible modern technique uses liquid-crystal (LC) shutters. When used in combination with cathode ray tube (CRT) displays, there is often leakage of light from the image intended for one eye into the view of the other eye. Such interocular crosstalk is 14% even in our state of the art CRT-based dichoptic system. While such crosstalk may have minimal impact on stereo movie or video game experiences, it can defeat clinical and research investigations. We use micromirror digital light processing (DLP) technology to create a novel dichoptic visual display system with substantially lower interocular crosstalk (0.3%; remaining crosstalk comes from the LC shutters). The DLP system normally uses a color wheel to display color images. Our approach is to disable the color wheel, synchronize the display directly to the computer's sync signal, allocate each of the three (former) color presentations to one or both eyes, and open and close the LC shutters in synchrony with those color events.
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Affiliation(s)
- Russell L Woods
- Schepens Eye Research Institute, Harvard Medical School, Boston, Massachusetts 02114, USA.
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37
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Abstract
Using a suprathreshold binocular summation paradigm developed by J. Ding and G. Sperling (2006, 2007) for normal observers, we investigated suprathreshold cyclopean perception in anisometropic amblyopia. In this paradigm, two suprathreshold sinewave gratings of the same spatial frequency but different spatial phases are presented to the left and right eyes of the observer. The perceived phase of the binocularly combined cyclopean image is measured as a function of the contrast ratio between the images in the two eyes. We found that both eyes contributed equally in normal subjects. However, stimulus of equal contrast was weighted much less in the amblyopic eye relative to the fellow eye in binocular combination. For the five amblyopes, the effective contrast of the amblyopic eye in binocular combination is equal to about 11%-28% of the same contrast presented to the fellow eye, much less than the ratio of contrast sensitivity between the two eyes (0.73-1.42). The results from the current study have many important implications in amblyopia research and treatment.
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Affiliation(s)
- Chang-Bing Huang
- Laboratory of Brain Processes (LOBES), Department of Psychology, USC, Los Angeles, CA, USA.
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38
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Howarth CM, Vorobyov V, Sengpiel F. Interocular Transfer of Adaptation in the Primary Visual Cortex. Cereb Cortex 2008; 19:1835-43. [DOI: 10.1093/cercor/bhn211] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Baker DH, Meese TS, Hess RF. Contrast masking in strabismic amblyopia: attenuation, noise, interocular suppression and binocular summation. Vision Res 2008; 48:1625-40. [PMID: 18547600 DOI: 10.1016/j.visres.2008.04.017] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2008] [Revised: 04/18/2008] [Accepted: 04/22/2008] [Indexed: 11/19/2022]
Abstract
To investigate amblyopic contrast vision at threshold and above we performed pedestal-masking (contrast discrimination) experiments with a group of eight strabismic amblyopes using horizontal sinusoidal gratings (mainly 3c/deg) in monocular, binocular and dichoptic configurations balanced across eye (i.e. five conditions). With some exceptions in some observers, the four main results were as follows. (1) For the monocular and dichoptic conditions, sensitivity was less in the amblyopic eye than in the good eye at all mask contrasts. (2) Binocular and monocular dipper functions superimposed in the good eye. (3) Monocular masking functions had a normal dipper shape in the good eye, but facilitation was diminished in the amblyopic eye. (4) A less consistent result was normal facilitation in dichoptic masking when testing the good eye, but a loss of this when testing the amblyopic eye. This pattern of amblyopic results was replicated in a normal observer by placing a neutral density filter in front of one eye. The two-stage model of binocular contrast gain control [Meese, T.S., Georgeson, M.A. & Baker, D.H. (2006). Binocular contrast vision at and above threshold. Journal of Vision 6, 1224-1243.] was 'lesioned' in several ways to assess the form of the amblyopic deficit. The most successful model involves attenuation of signal and an increase in noise in the amblyopic eye, and intact stages of interocular suppression and binocular summation. This implies a behavioural influence from monocular noise in the amblyopic visual system as well as in normal observers with an ND filter over one eye.
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Affiliation(s)
- Daniel H Baker
- School of Life and Health Sciences, Aston University, Birmingham, UK.
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40
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Whatham AR, Judge SJ. Rotated prism-wear disrupts emmetropization but does not reliably induce hyperopia in the New World monkey. Vision Res 2007; 47:3324-34. [PMID: 17967473 DOI: 10.1016/j.visres.2007.09.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2006] [Revised: 09/13/2007] [Accepted: 09/18/2007] [Indexed: 11/28/2022]
Abstract
To determine whether a disruption of binocular vision that has been previously shown to be amblyogenic disturbs visually guided growth, and in particular to follow-up the observation by Kiorpes and Wallman [Kiorpes, L., & Wallman, J. (1995). Does experimentally-induced amblyopia cause hyperopia in monkeys? Vision Research, 35(9), 1289-1297] that monkeys in whom strabismus had been induced some years earlier were hyperopic in eyes that had become amblyopic, we induced unilateral fixation in five infant New World monkeys (marmosets) through the wearing of a Fresnel prism (of 15 or 30 prism dioptres power) in front of one eye for four weeks. The prism was rotated every three hours during the prism-wear period to encourage a preference for fixating with the contralateral eye. Refractive error and intraocular axial dimensions were measured before, and at intervals after the prism-wearing period. Fixation preference was measured behaviourally, during and after the prism-wear period. Cortical visual function was subsequently assessed through recording of pattern-reversal VEPs in each marmoset between 11 and 14 months of age to assess whether amblyopia had developed in the non-fixing eye. All marmosets used the untreated eye almost exclusively for a monocular visual task by the end of the prism-rearing period. This preference was still present up to at least 7 months after prism-wear had ceased. VEP measures showed a loss of sensitivity at low spatial frequencies (the only ones we were able to test), compatible with amblyopia having developed in the non-fixating eyes of the prism-reared marmosets. Eyes that wore prisms were not significantly different from their fellow eyes in mean refractive error or mean vitreous chamber depth (repeated measures ANOVA; P>0.05) before or at any time after prism-wear had ceased. Two marmosets developed 2-3D of anisometropia (one hyperopic and one myopic) at the end of prism-wear, that was attributable to interocular differences in vitreous chamber depth, and which decreased towards isometropia in the period following prism-wear removal. Disruption of binocular vision with rotating prisms can influence emmetropization and ocular growth, although it does not appear to do so in a consistent way.
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Affiliation(s)
- Andrew R Whatham
- University of Oxford, Department of Physiology, Anatomy, & Genetics, Sherrington Building, Parks Road, OX1 3PT Oxford, UK
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Baker DH, Meese TS. Binocular contrast interactions: dichoptic masking is not a single process. Vision Res 2007; 47:3096-107. [PMID: 17904610 DOI: 10.1016/j.visres.2007.08.013] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2007] [Revised: 08/21/2007] [Accepted: 08/22/2007] [Indexed: 11/18/2022]
Abstract
To decouple interocular suppression and binocular summation we varied the relative phase of mask and target in a 2IFC contrast-masking paradigm. In Experiment I, dichoptic mask gratings had the same orientation and spatial frequency as the target. For in-phase masking, suppression was strong (a log-log slope of approximately 1) and there was weak facilitation at low mask contrasts. Anti-phase masking was weaker (a log-log slope of approximately 0.7) and there was no facilitation. A two-stage model of contrast gain control [Meese, T.S., Georgeson, M.A. and Baker, D.H. (2006). Binocular contrast vision at and above threshold. Journal of Vision, 6: 1224-1243] provided a good fit to the in-phase results and fixed its free parameters. It made successful predictions (with no free parameters) for the anti-phase results when (A) interocular suppression was phase-indifferent but (B) binocular summation was phase sensitive. Experiments II and III showed that interocular suppression comprised two components: (i) a tuned effect with an orientation bandwidth of approximately +/-33 degrees and a spatial frequency bandwidth of >3 octaves, and (ii) an untuned effect that elevated threshold by a factor of between 2 and 4. Operationally, binocular summation was more tightly tuned, having an orientation bandwidth of approximately +/-8 degrees , and a spatial frequency bandwidth of approximately 0.5 octaves. Our results replicate the unusual shapes of the in-phase dichoptic tuning functions reported by Legge [Legge, G.E. (1979). Spatial frequency masking in human vision: Binocular interactions. Journal of the Optical Society of America, 69: 838-847]. These can now be seen as the envelope of the direct effects from interocular suppression and the indirect effect from binocular summation, which contaminates the signal channel with a mask that has been suppressed by the target.
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Affiliation(s)
- Daniel H Baker
- School of Life and Health Sciences, Aston University, Birmingham, UK.
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Conner IP, Odom JV, Schwartz TL, Mendola JD. Monocular activation of V1 and V2 in amblyopic adults measured with functional magnetic resonance imaging. J AAPOS 2007; 11:341-50. [PMID: 17434776 PMCID: PMC2174609 DOI: 10.1016/j.jaapos.2007.01.119] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/20/2006] [Revised: 01/15/2007] [Accepted: 01/15/2007] [Indexed: 10/23/2022]
Abstract
PURPOSE Although previous neuroimaging efforts clearly indicate visual cortical dysfunction in adults with amblyopia, the extent of abnormalities remains unclear. METHODS This functional magnetic resonance imaging (fMRI) study directly compared activity in visual cortex produced by monocular stimulation in 18 adults (six esotropic strabismics, six anisometropes, and six controls). Measures were made in three cortical regions-of-interest, individually defined using standard retinotopic mapping techniques in the nonamblyopic eye, corresponding to extrafoveal V1, extrafoveal V2, and the foveal representation at the occipital pole. Fixation stability was monitored and found not to differ significantly between subject groups. RESULTS Overall results showed depressed fMRI signal magnitude for amblyopic eyes compared with sound eyes, although a few subjects did not show this trend. Assessment of the spatial extent of activation using an ocular dominance index did show significantly larger interocular differences for both strabismics and anisometropes compared with control subjects for whom eye dominance was carefully defined. In addition, both amblyopic groups showed less cortical area able to be significantly driven by either eye. The magnitude of these effects was equivalent in V1, V2, and the foveal representation, as well as between amblyopic groups. No difference was detected in the strength of signal from the nasal versus temporal retina in either amblyopic group. CONCLUSIONS Asymmetries in magnitude of monocular activation do occur in subjects with amblyopia, but these basic measures are limited in terms of sensitivity for mild to moderate amblyopia and for specificity between subtypes.
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Affiliation(s)
- Ian P Conner
- Department of Neurobiology and Anatomy, West Virginia University, Morgantown, West Virginia 26505, USA.
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Conner IP, Odom JV, Schwartz TL, Mendola JD. Retinotopic maps and foveal suppression in the visual cortex of amblyopic adults. J Physiol 2007; 583:159-73. [PMID: 17627994 PMCID: PMC2277220 DOI: 10.1113/jphysiol.2007.136242] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Amblyopia is a developmental visual disorder associated with loss of monocular acuity and sensitivity as well as profound alterations in binocular integration. Abnormal connections in visual cortex are known to underlie this loss, but the extent to which these abnormalities are regionally or retinotopically specific has not been fully determined. This functional magnetic resonance imaging (fMRI) study compared the retinotopic maps in visual cortex produced by each individual eye in 19 adults (7 esotropic strabismics, 6 anisometropes and 6 controls). In our standard viewing condition, the non-tested eye viewed a dichoptic homogeneous mid-level grey stimulus, thereby permitting some degree of binocular interaction. Regions-of-interest analysis was performed for extrafoveal V1, extrafoveal V2 and the foveal representation at the occipital pole. In general, the blood oxygenation level-dependent (BOLD) signal was reduced for the amblyopic eye. At the occipital pole, population receptive fields were shifted to represent more parafoveal locations for the amblyopic eye, compared with the fellow eye, in some subjects. Interestingly, occluding the fellow eye caused an expanded foveal representation for the amblyopic eye in one early-onset strabismic subject with binocular suppression, indicating real-time cortical remapping. In addition, a few subjects actually showed increased activity in parietal and temporal cortex when viewing with the amblyopic eye. We conclude that, even in a heterogeneous population, abnormal early visual experience commonly leads to regionally specific cortical adaptations.
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Affiliation(s)
- Ian P Conner
- Center for Advanced Imaging, West Virginia University Health Sciences Center, Morgantown, WV 26506-9236, USA
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Huang PC, Hess RF, Dakin SC. Flank facilitation and contour integration: different sites. Vision Res 2006; 46:3699-706. [PMID: 16806389 DOI: 10.1016/j.visres.2006.04.025] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2006] [Revised: 04/14/2006] [Accepted: 04/28/2006] [Indexed: 10/24/2022]
Abstract
Observers' ability to integrate features into extended contours, and to exploit the flanking structure to facilitate contrast detection (flank facilitation), exhibit a similar dependence on element spacing and orientation. Here, we investigate whether this reflects the operation of a common cortical mechanism by comparing performance for both tasks under monocular, binocular, dichoptic, and stereoscopic viewing conditions. Our results clearly implicate different cortical sites for flank-facilitated detection and contour integration; the former is a purely monocular phenomenon and must therefore occur at the earliest stages of cortical processing. In contrast, contour integration is a binocular process and occurs after the encoding of relative disparity, suggesting substantial extra-striate involvement. We conclude that the sites, and therefore the mechanisms, underlying these two seemingly related psychophysical phenomena are different.
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Affiliation(s)
- Pi-Chun Huang
- McGill Vision Research, Department of Ophthalmology, McGill University, Montreal, Que, Canada.
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Justo MS, Bermudez MA, Perez R, Gonzalez F. Binocular interaction and performance of visual tasks. Ophthalmic Physiol Opt 2004; 24:82-90. [PMID: 15005672 DOI: 10.1046/j.1475-1313.2003.00173.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Binocular vision implies the fusion of the right and left retinal images to perceive a single image. For this, interocular interaction is required. We measured the reaction times to carry out a visual fixation task in order to determine whether binocular interaction influences performance. Several combinations of test and distraction stimuli were monocularly and binocularly presented to one monkey and three human subjects. The overall median reaction times were 340 ms for the animal and 308, 342 and 381 for human subjects 1, 2 and 3 respectively. Reaction time was shorter when the test stimulus was presented binocularly. Moreover, we observed that the presence of a distraction stimulus increased the reaction time and that a correlated distraction stimulus had a greater influence on this increase than an uncorrelated distraction stimulus. These findings indicate that with binocular vision a more rapid performance of a visual task occurs.
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Affiliation(s)
- Maria S Justo
- Department of Physiology, Laboratorios Ramon Dominguez, School of Medicine, University of Santiago de Compostela, E-15782 Spain.
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Zhang B, Matsuura K, Mori T, Wensveen JM, Harwerth RS, Smith EL, Chino Y. Binocular Deficits Associated With Early Alternating Monocular Defocus. II. Neurophysiological Observations. J Neurophysiol 2003; 90:3012-23. [PMID: 14615425 DOI: 10.1152/jn.00975.2002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Experiencing binocularly conflicting signals early in life dramatically alters the binocular responses of cortical neurons. Because visual cortex is highly plastic during a critical period of development, cortical deficits resulting from early abnormal visual experience often mirror the nature of interocular decorrelation of neural signals from the two eyes. In the preceding paper, we demonstrated that monkeys that experienced early alternating monocular defocus (–1.5, –3.0, or –6.0 D) show deficits in stereopsis that generally reflected the magnitude of imposed monocular defocus. Because these results indicated that alternating monocular defocus affected the higher spatial frequency components of visual scenes more severely, we employed microelectrode recording methods to investigate whether V1 neurons in these lens-reared monkeys exhibited spatial-frequency-dependent alterations in their binocular response properties. We found that a neuron's sensitivity to interocular spatial phase disparity was reduced in the treated monkeys and that this reduction was generally more severe for units tuned to higher spatial frequencies. In the majority of the affected units, the disparity-sensitivity loss was associated with interocular differences in monocular receptive field properties. The present results suggest that the behavioral deficits in stereopsis produced by abnormal visual experience reflect at least in part the constraints imposed by alterations at the earliest stages of binocular cortical processing and support the hypothesis that the local disparity processing mechanisms in primates are spatially tuned and can be independently compromised by early abnormal visual experience.
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Affiliation(s)
- Bin Zhang
- College of Optometry, University of Houston, Houston, Texas 77204-2020, USA
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Abstract
Patients with strabismus or anisometropic amblyopia fixate and attend with one eye and suppress the image from the other eye. Here we use a visual evoked potential technique to show that patients who lack normal stereopsis retain suppressive binocular interactions but lack a characteristic form of non-linear binocular interaction that is present in normal observers. Oscillating grating targets presented at different temporal frequencies in the two eyes evoke a strong response in normal observers at a frequency equal to the sum of the two input frequencies for fusable targets but not for rivalrous ones. However increasing contrast in one eye reduces the response amplitude from the other eye under either fusable (dichoptic masking) or rivalrous conditions. Stereo-deficient observers lack the sum-frequency response, but retain dichoptic masking interactions. Dichoptic masking is stronger when the masker is presented to the patients' dominant rather than non-dominant eyes, suggesting that a subset of preserved binocular inhibitory interactions form the basis of clinical suppression.
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Affiliation(s)
- A M Norcia
- Smith Kettlewell Eye Research Institute, San Francisco, CA 94115, USA
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Abstract
Stereo matching can intervene to prevent dichoptic masking. In a dichoptic masking paradigm we measured the contrast threshold for a bar target, presented to one eye, as a function of the contrast of an identical masking bar, presented at retinal correspondence in the other eye. Confirming previous studies of dichoptic masking with sinusoidal gratings, the test bar thresholds rose proportionally with increasing masking contrast. This threshold elevation was almost nullified when an extra bar was presented to the eye seeing the test stimulus. Release from masking occurred when the disparity between the masking bar and extra bar was < 20 min arc over a range of contrast levels (8-45%), and for bars containing either broad spatial frequency spectra or bars with only high spatial frequencies (peak = 12 c/deg). The latter result rules out an explanation for the release from masking based on contrast discrimination in low spatial frequency channels. The extra bar was effective in releasing the test bar from masking as long as the extra bar's contrast was greater than about one-fifth the contrast of the mask, a result that suggests that there is a contrast threshold for stereo matching. We interpret our findings to indicate that a stage of stereo matching occurs prior to the neural site limiting dichoptic contrast discrimination.
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Affiliation(s)
- S P McKee
- Smith-Kettlewell Eye Research Institute, San Francisco, CA 94115
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Abstract
Observers with normal stereopsis suppress some of the monocular information contained in each stereo half-image, a phenomenon we call fusional suppression. We measured vernier acuity for an ordinary vertical vernier test target, presented to one eye, that was paired stereoscopically with a vernier target with a large fixed offset, presented to the other eye. The size of the fixed offset, and hence, the disparity of the upper target line, was varied parametrically. Vernier thresholds for the test target rose as a function of disparity, reaching a maximum at 20 min of disparity and then decreasing gradually as the disparity exceeded the limits of foveal fusion (40-60 min arc). In the two normal observers, fusional suppression was symmetrical; neither eye had good access to monocular information. In the stereoanomalous observers, fusional suppression was not symmetrical. When they viewed the vernier test target with the stronger of their two eyes, their vernier thresholds were barely affected by the stereo half-image in the other eye, and so were better than those of the normal observers measured in the same condition. When the stereoanomalous observers viewed the test target with their weaker eye, their fusional suppression was similar in range and magnitude to the suppression found in normal observers. Amblyopic suppression in mild amblyopes may be a residual effect of normal fusional suppression, operating to suppress monocular signals in the weaker eye, without conferring the benefits of normal stereopsis and fusion.
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Affiliation(s)
- S P McKee
- Smith-Kettlewell Eye Research Institute, San Francisco, CA 94115
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Odom JV, Harter MR. Interocular suppression in adults and infants using anaglyphic stimuli: visually evoked potential measures. ELECTROENCEPHALOGRAPHY AND CLINICAL NEUROPHYSIOLOGY 1983; 56:232-43. [PMID: 6191954 DOI: 10.1016/0013-4694(83)90077-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Interocular suppression, assessed by monocular VEP amplitude reduction, was investigated in 3 infants, average age of 3 months, and 8 adults. A dichoptic simultaneous masking paradigm was employed, the two eyes being disassociated by red and green filters which transmitted non-overlapping wave lengths of light (anaglyphic method). One eye was continuously presented with either darkness, a diffuse green light, or two green dot patterns, containing either 20' or 80' dots. The other eye was flashed with either red diffuse light, a red 20' dot pattern, or a red 80' dot pattern. In both adults and infants, monocular VEP amplitude was reduced as the size of the continuously presented dots increased (pattern suppression) and a smaller amplitude response occurred when dots of equal size were presented than when data of different size were presented (size-specific suppression). The relative and absolute magnitudes of interocular pattern suppression were similar for adults and infants. However, the relative and absolute magnitudes of size-specific suppression were larger for adults than for infants. Pattern interocular suppression was inferred to be relatively more mature in 3 month olds than size-specific suppression. The relative lack of size-specific suppression suggests a relative immaturity of binocular spatial frequency or size channels.
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