Amblyopic Deficit Beyond the Fovea: Delayed and Variable Single-Trial ERP Response Latencies, but Unaltered Amplitudes

Bankó, Éva M.; Körtvélyes, Judit; Németh, János; Vidnyánszky, Zoltán

doi:10.1167/iovs.13-13507

Cited by 8 publications

(4 citation statements)

References 38 publications

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“…Neural response times are also delayed when viewing with the amblyopic eye. Visual evoked responses to fine gratings or checkerboards typically show both reduced amplitudes and increased latencies of the early components (Lombroso, Duffy, & Robb, 1969 ; Spekreijse, Khoe, & van der Tweel, 1972 ; Sokol & Bloom, 1973 ; Tuttle, 1973 ; Arden, Barnard, & Mushin, 1974 ; Yinon, Jakobovitz, & Auerbach, 1974 ; Levi, 1975 ; Levi & Harwerth, 1978a ; Levi & Harwerth, 1978b ; Sokol & Nadler, 1979 ; Manny & Levi, 1982 ; Bankó, Körtvélyes, Németh, Weiss, & Vidnyánszky, 2013 ; Bankó, Körtvélyes, Németh, & Vidnyánszky, 2014 ). Interestingly, a recent study found that amplitudes were reduced only with foveal stimulation but not with cortically scaled perifoveal stimulation, while responses were delayed and more variable at both the fovea and perifovea (Bankó et al, 2014 ).…”

Section: Introductionmentioning

confidence: 99%

Both saccadic and manual responses in the amblyopic eye of strabismics are irreducibly delayed

et al. 2018

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Abnormal early visual development can result in a constellation of neural and visual deficits collectively known as amblyopia. Among the many deficits, a common finding is that both saccadic and manual reaction times to targets presented to the amblyopic eye are substantially delayed when compared to the fellow eye or to normal eyes. Given the well-known deficits in contrast sensitivity in the amblyopic eye, a natural question is whether the prolonged reaction times are simply a consequence of reduced stimulus visibility. To address this question, in Experiment 1 we measure saccadic reaction times (RT) to perifoveal stimuli as a function of effective stimulus contrast (i.e., contrast scaled by the amblyopic eye's contrast threshold). We find that when sensory differences between the eyes are minimized, the asymptotic RTs of our anisometropic amblyopes were similar in the two eyes. However, our results suggest that some strabismic amblyopes have an irreducible delay at the asymptote. That is, even when the sensory differences of the stimulus were accounted for, these observers still had large interocular differences (on average, 77 ms) in saccadic reaction time. In Experiment 2, to assess the role of fixation on saccadic reaction time we compared reaction time with and without a foveal target (the “gap effect”). Our results suggest that, while removing the fixation target does indeed speed up reaction time in the amblyopic eye, the gap effect is similar in the two eyes. Therefore, the gap effect does not eliminate the irreducible delay in the amblyopic eye. Finally, in Experiment 3 we compared the interocular differences in saccadic and manual reaction times in the same observers. This allowed us to determine the relationship between the latencies in the two modalities. We found a strong correlation between the differences in saccadic and manual reaction times; however, the manual RT difference is about half that of saccadic RT, suggesting that there may be two separable effects on saccadic reaction time: (a) a central problem with directing actions to a target, related to disengagement of attention at the fovea, which results in delays in both saccadic and manual reaction times, and (b) a further delay in saccadic reaction times because of the motor refractory period from a previous saccade or microsaccade, made in an attempt to stabilize the amblyopic eye of strabismics.

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Section: Introductionmentioning

confidence: 99%

Both saccadic and manual responses in the amblyopic eye of strabismics are irreducibly delayed

et al. 2018

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“…These deficits include enhanced crowding as well as problems with stimulus localization, contour integration, texture and second-order pattern perception, shape discrimination, motion sensitivity, stereopsis, eye movements, and oculomotor coordination. Although typically characterized as a foveal visual disorder, amblyopia-related deficits and their neural markers are present across the visual field, including the perifovea (Bankó, Körtvélyes, Németh, & Vidnyánszky, 2014; Ho et al, 2006; Hou, Kim, Lai, & Verghese, 2016; Katz, Levi, & Bedell, 1984). …”

Section: Introductionmentioning

confidence: 99%

Covert spatial attention is functionally intact in amblyopic human adults

et al. 2016

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Certain abnormalities in behavioral performance and neural signaling have been attributed to a deficit of visual attention in amblyopia, a neurodevelopmental disorder characterized by a diverse array of visual deficits following abnormal binocular childhood experience. Critically, most have inferred attention's role in their task without explicitly manipulating and measuring its effects against a baseline condition. Here, we directly investigate whether human amblyopic adults benefit from covert spatial attention—the selective processing of visual information in the absence of eye movements—to the same degree as neurotypical observers. We manipulated both involuntary (Experiment 1) and voluntary (Experiment 2) attention during an orientation discrimination task for which the effects of covert spatial attention have been well established in neurotypical and special populations. In both experiments, attention significantly improved accuracy and decreased reaction times to a similar extent (a) between the eyes of the amblyopic adults and (b) between the amblyopes and their age- and gender-matched controls. Moreover, deployment of voluntary attention away from the target location significantly impaired task performance (Experiment 2). The magnitudes of the involuntary and voluntary attention benefits did not correlate with amblyopic depth or severity. Both groups of observers showed canonical performance fields (better performance along the horizontal than vertical meridian and at the lower than upper vertical meridian) and similar effects of attention across locations. Despite their characteristic low-level vision impairments, covert spatial attention remains functionally intact in human amblyopic adults.

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“…For each eye position measurement (i.e., a pair of [x,y] coordinates), geometrical distance from the fixation point was calculated. The median distance was used as a measure of fixation stability in each subject separately for each eye with higher distance values meaning less stable fixation 66 , 67 . In addition, we have also calculated to more standard bivariate contour ellipse area (BCEA), which however suffers from normality assumptions and assumes fixation data is elliptically distributed, as opposed to the assumption free distance calculation 67 .…”

Section: Methodsmentioning

confidence: 99%

Fixation instability, astigmatism, and lack of stereopsis as factors impeding recovery of binocular balance in amblyopia following binocular therapy

Bankó

Barboni

Markó

et al. 2022

Sci Rep

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Dichoptic therapy is a promising method for improving vision in pediatric and adult patients with amblyopia. However, a systematic understanding about changes in specific visual functions and substantial variation of effect among patients is lacking. Utilizing a novel stereoscopic augmented-reality based training program, 24 pediatric and 18 adult patients were trained for 20 h along a three-month time course with a one-month post-training follow-up for pediatric patients. Changes in stereopsis, distance and near visual acuity, and contrast sensitivity for amblyopic and fellow eyes were measured, and interocular differences were analyzed. To reveal what contributes to successful dichoptic therapy, ANCOVA models were used to analyze progress, considering clinical baseline parameters as covariates that are potential requirements for amblyopic recovery. Significant and lasting improvements have been achieved in stereoacuity, interocular near visual acuity, and interocular contrast sensitivity. Importantly, astigmatism, fixation instability, and lack of stereopsis were major limiting factors for visual acuity, stereoacuity, and contrast sensitivity recovery, respectively. The results demonstrate the feasibility of treatment-efficacy prediction in certain aspects of dichoptic amblyopia therapy. Furthermore, our findings may aid in developing personalized therapeutic protocols, capable of considering individual clinical status, to help clinicians in tailoring therapy to patient profiles for better outcome.

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Amblyopic Deficit Beyond the Fovea: Delayed and Variable Single-Trial ERP Response Latencies, but Unaltered Amplitudes

Cited by 8 publications

References 38 publications

Both saccadic and manual responses in the amblyopic eye of strabismics are irreducibly delayed

Both saccadic and manual responses in the amblyopic eye of strabismics are irreducibly delayed

Covert spatial attention is functionally intact in amblyopic human adults

Fixation instability, astigmatism, and lack of stereopsis as factors impeding recovery of binocular balance in amblyopia following binocular therapy

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