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Daphne Maurer - One of the best experts on this subject based on the ideXlab platform.
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feasibility of a school based vision screening program to detect undiagnosed Visual problems in kindergarten children in ontario
Canadian Medical Association Journal, 2020Co-Authors: Mayu Nishimura, Agnes M F Wong, Hele Dimaras, Daphne MaurerAbstract:BACKGROUND: Visual problems can negatively affect Visual Development and learning but often go undetected. We assessed the feasibility of scaling up a school-based screening program to identify and treat kindergarten children with Visual problems. METHODS: We conducted a prospective cohort study offering vision screening to junior (JK) and senior kindergarten (SK) children attending 43 schools in 15 Ontario communities. Screening comprised photoscreeners and tests of Visual acuity, stereoacuity and eye alignment. Children who failed any test were referred for a comprehensive eye examination, with treatment as needed (e.g., glasses). RESULTS: Using a passive consent model, 89% of children were screened compared with 62% using an active consent model (p INTERPRETATION: Many children in Ontario with a Visual problem were not being identified by the status quo in 2015–2017. We found that in-school vision screening with follow-up eye examinations is an effective strategy for identifying at-risk children and placing them in eye care before grade 1.
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amblyopia background to the special issue on stroke recovery
Developmental Psychobiology, 2012Co-Authors: Daphne Maurer, Takao K HenschAbstract:In this introductory article, we summarize the evidence from humans and animal models on the shaping of postnatal Visual Development by focused binocular input. When balanced input is missing during a sensitive period, deficits emerge, including seemingly permanent impairments in Visual acuity that are labeled amblyopia. Rodent models have identified neurochemical changes that control the onset of such sensitive periods and molecular and structural brakes that lead to the diminution of the plasticity thereafter. Both animal and human studies of amblyopia have recently identified exciting ways to remediate vision in adulthood that bear some similarity to the interventions that have proved successful in promoting recovery from stroke.
Mayu Nishimura - One of the best experts on this subject based on the ideXlab platform.
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feasibility of a school based vision screening program to detect undiagnosed Visual problems in kindergarten children in ontario
Canadian Medical Association Journal, 2020Co-Authors: Mayu Nishimura, Agnes M F Wong, Hele Dimaras, Daphne MaureAbstract:BACKGROUND: Visual problems can negatively affect Visual Development and learning but often go undetected. We assessed the feasibility of scaling up a school-based screening program to identify and treat kindergarten children with Visual problems. METHODS: We conducted a prospective cohort study offering vision screening to junior (JK) and senior kindergarten (SK) children attending 43 schools in 15 Ontario communities. Screening comprised photoscreeners and tests of Visual acuity, stereoacuity and eye alignment. Children who failed any test were referred for a comprehensive eye examination, with treatment as needed (e.g., glasses). RESULTS: Using a passive consent model, 89% of children were screened compared with 62% using an active consent model (p INTERPRETATION: Many children in Ontario with a Visual problem were not being identified by the status quo in 2015–2017. We found that in-school vision screening with follow-up eye examinations is an effective strategy for identifying at-risk children and placing them in eye care before grade 1.
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feasibility of a school based vision screening program to detect undiagnosed Visual problems in kindergarten children in ontario
Canadian Medical Association Journal, 2020Co-Authors: Mayu Nishimura, Agnes M F Wong, Hele Dimaras, Daphne MaurerAbstract:BACKGROUND: Visual problems can negatively affect Visual Development and learning but often go undetected. We assessed the feasibility of scaling up a school-based screening program to identify and treat kindergarten children with Visual problems. METHODS: We conducted a prospective cohort study offering vision screening to junior (JK) and senior kindergarten (SK) children attending 43 schools in 15 Ontario communities. Screening comprised photoscreeners and tests of Visual acuity, stereoacuity and eye alignment. Children who failed any test were referred for a comprehensive eye examination, with treatment as needed (e.g., glasses). RESULTS: Using a passive consent model, 89% of children were screened compared with 62% using an active consent model (p INTERPRETATION: Many children in Ontario with a Visual problem were not being identified by the status quo in 2015–2017. We found that in-school vision screening with follow-up eye examinations is an effective strategy for identifying at-risk children and placing them in eye care before grade 1.
Benjamin Thompson - One of the best experts on this subject based on the ideXlab platform.
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interocular suppression in strabismic amblyopia results in an attenuated and delayed hemodynamic response function in early Visual cortex
Journal of Vision, 2011Co-Authors: Reza Farivar, Benjamin Thompson, Behzad Mansouri, Robert F. HessAbstract:Factors such as strabismus or anisometropia during infancy can disrupt normal Visual Development and result in amblyopia, characterized by reduced Visual function in an otherwise healthy eye and often associated with persistent suppression of inputs from the amblyopic eye by those from the dominant eye. It has become evident from fMRI studies that the cortical response to stimulation of the amblyopic eye is also affected. We were interested to compare the hemodynamic response function (HRF) of early Visual cortex to amblyopic vs. dominant eye stimulation. In the first experiment, we found that stimulation of the amblyopic eye resulted in a signal that was both attenuated and delayed in its time to peak. We postulated that this delay may be due to suppressive effects of the dominant eye and, in our second experiment, measured the cortical response of amblyopic eye stimulation under two conditions--where the dominant eye was open and seeing a static pattern (high suppression) or where the dominant eye was patched and closed (low suppression). We found that the HRF in response to amblyopic eye stimulation depended on whether the dominant eye was open. This effect was manifested as both a delayed HRF under the suppressed condition and an amplitude reduction.
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a new binocular approach to the treatment of amblyopia in adults well beyond the critical period of Visual Development
Restorative Neurology and Neuroscience, 2010Co-Authors: Behzad Mansouri, Benjamin ThompsonAbstract:PURPOSE: The present treatments for amblyopia are predominantly monocular aiming to improve the vision in the amblyopic eye through either patching of the fellow fixing eye or Visual training of the amblyopic eye. This approach is problematic, not least of which because it rarely results in establishment of binocular function. Recently it has shown that amblyopes possess binocular cortical mechanisms for both threshold and suprathreshold stimuli. METHODS: We outline a novel procedure for measuring the extent to which the fixing eye suppresses the fellow amblyopic eye, rendering what is a structurally binocular system, functionally monocular. RESULTS: Here we show that prolonged periods of viewing (under the artificial conditions of stimuli of different contrast in each eye) during which information from the two eyes is combined leads to a strengthening of binocular vision in strabismic amblyopes and eventual combination of binocular information under natural viewing conditions (stimuli of the same contrast in each eye). Concomitant improvement in monocular acuity of the amblyopic eye occurs with this reduction in suppression and strengthening of binocular fusion. Furthermore, in a majority of patients tested, stereoscopic function is established. CONCLUSIONS: This provides the basis for a new treatment of amblyopia, one that is purely binocular and aimed at reducing suppression as a first step.
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a new binocular approach to the treatment of amblyopia in adults well beyond the critical period of Visual Development
Restorative Neurology and Neuroscience, 2010Co-Authors: Behzad Mansouri, Benjamin ThompsonAbstract:Background: The present treatments for amblyopia are predominately monocular aiming to improve the vision in the amblyopic eye through either patching of the fellow fixing eye or Visual training of the amblyopic eye. This approach is problematic, not least of which because it rarely results in establishment of binocular function. Recently it has shown that amblyopes possess binocular cortical mechanisms for both threshold and suprathreshold stimuli. Objectives: We have outline a novel procedure for measuring the extent to which the fixing eye suppresses the fellow amblyopic eye, rendering what is a structurally binocular system, functionally monocular. Results: Here we show that prolonged periods of viewing (under the artificial conditions of stimuli of different contrast in each eye) during which information from the two eyes iscombined leads to astrengthening ofbinocular vision in strabismic amblyopes and eventual combination of binocular information under natural viewing conditions (stimuli of the same contrast in each eye). Concomitant improvement in monocular acuity of the amblyopic eye occurs with this reduction in suppression and strengthening of binocular fusion. Furthermore, in a majority of patients tested, stereoscopic function is established. Conclusions: This provides the basis for a new treatment of amblyopia, one that is purely binocular and aimed at reducing suppression as a first step.
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deficient responses from the lateral geniculate nucleus in humans with amblyopia
European Journal of Neuroscience, 2009Co-Authors: Robert F. Hess, Benjamin Thompson, Glen A Gole, Kathy T MullenAbstract:Amblyopia or lazy eye is the most common cause of uniocular blindness in adults. It is caused by a disruption to normal Visual Development as a consequence of unmatched inputs from the two eyes in early life, arising from a turned eye (strabismus), unequal refractive error (anisometropia) or form deprivation (e.g. cataract). Animal models based on extracellular recordings in anesthetized animals suggest that the earliest site of the anomaly in the primate Visual pathway is the primary Visual cortex (corresponding to the striate cortex, cytoarchitectonic area 17 and area V1), which is where inputs from the two eyes are first combined in an excitatory fashion, whereas more distal and monocular processing structures such as the retina and lateral geniculate nucleus (LGN) are normal. Using high-field functional magnetic resonance imaging in a group of human adults with amblyopia, we demonstrate that functional deficits are first observable at a thalamic level, that of the LGN. Our results suggest the need to re-evaluate the current models of amblyopia that are based on the assumption of a purely cortical dysfunction, as well as the role for the LGN in Visual Development.
Robert F. Hess - One of the best experts on this subject based on the ideXlab platform.
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real time modulation of perceptual eye dominance in humans
Proceedings of The Royal Society B: Biological Sciences, 2014Co-Authors: Jiawei Zhou, Alexandre Reynaud, Robert F. HessAbstract:Ocular dominance (OD) has long served as the model for neural plasticity. The shift of OD has been demonstrated by monocular deprivation in animals only during early Visual Development. Here, for the first time, we show that perceptual eye dominance can be modulated in real time in normal human adults by varying the spatial image content of movies seen dichoptically by the two eyes over a period as short as 2.5 h. Unlike OD shifts seen in early Visual Development, this modulation in human eye dominance is not simply a consequence of reduced interocular correlation (e.g. synchronicity) or overall contrast energy, but due to the amplitude reductions of specific image components in one eye's view. The spatial properties driving this eye dominance change suggest that the underlying mechanism is binocular but not orientationally selective, therefore uniquely locating it to layer 4 B of area V1.
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interocular suppression in strabismic amblyopia results in an attenuated and delayed hemodynamic response function in early Visual cortex
Journal of Vision, 2011Co-Authors: Reza Farivar, Benjamin Thompson, Behzad Mansouri, Robert F. HessAbstract:Factors such as strabismus or anisometropia during infancy can disrupt normal Visual Development and result in amblyopia, characterized by reduced Visual function in an otherwise healthy eye and often associated with persistent suppression of inputs from the amblyopic eye by those from the dominant eye. It has become evident from fMRI studies that the cortical response to stimulation of the amblyopic eye is also affected. We were interested to compare the hemodynamic response function (HRF) of early Visual cortex to amblyopic vs. dominant eye stimulation. In the first experiment, we found that stimulation of the amblyopic eye resulted in a signal that was both attenuated and delayed in its time to peak. We postulated that this delay may be due to suppressive effects of the dominant eye and, in our second experiment, measured the cortical response of amblyopic eye stimulation under two conditions--where the dominant eye was open and seeing a static pattern (high suppression) or where the dominant eye was patched and closed (low suppression). We found that the HRF in response to amblyopic eye stimulation depended on whether the dominant eye was open. This effect was manifested as both a delayed HRF under the suppressed condition and an amplitude reduction.
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deficient responses from the lateral geniculate nucleus in humans with amblyopia
European Journal of Neuroscience, 2009Co-Authors: Robert F. Hess, Benjamin Thompson, Glen A Gole, Kathy T MullenAbstract:Amblyopia or lazy eye is the most common cause of uniocular blindness in adults. It is caused by a disruption to normal Visual Development as a consequence of unmatched inputs from the two eyes in early life, arising from a turned eye (strabismus), unequal refractive error (anisometropia) or form deprivation (e.g. cataract). Animal models based on extracellular recordings in anesthetized animals suggest that the earliest site of the anomaly in the primate Visual pathway is the primary Visual cortex (corresponding to the striate cortex, cytoarchitectonic area 17 and area V1), which is where inputs from the two eyes are first combined in an excitatory fashion, whereas more distal and monocular processing structures such as the retina and lateral geniculate nucleus (LGN) are normal. Using high-field functional magnetic resonance imaging in a group of human adults with amblyopia, we demonstrate that functional deficits are first observable at a thalamic level, that of the LGN. Our results suggest the need to re-evaluate the current models of amblyopia that are based on the assumption of a purely cortical dysfunction, as well as the role for the LGN in Visual Development.
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the spatial localization deficit in Visually deprived kittens
Vision Research, 2005Co-Authors: Guy Gingras, Donald E Mitchell, Robert F. HessAbstract:We measured the spatial localization abilities (alignment accuracy) of Visually deprived kittens by use of similar spatially bandpass stimuli (Gaussian blobs) to those employed for the assessment of human amblyopes. The tests of vision were conducted on kittens reared with either strabismus or following different periods of monocular deprivation. As with amblyopic humans, the deficits in alignment accuracy were scaled in proportion to blob size and were not only considerably larger than those of grating acuity but also were not correlated with either the acuity or contrast sensitivity losses. Tests with stimuli of various contrast revealed that the deficits could not be explained in terms of the contrast sensitivity loss in this eye. The positional deficits that arise from anomalous Visual Development are independent of the contrast sensitivity loss and profound.
Kira Fleischer Michaelsen - One of the best experts on this subject based on the ideXlab platform.
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effect of formula supplemented with docosahexaenoic acid andγ linolenic acid on fatty acid status and Visual acuity in term infants
Journal of Pediatric Gastroenterology and Nutrition, 1998Co-Authors: Marianne Horby Jorgensen, Gunhild Holmer, Pia Lund, Olle Hernell, Kira Fleischer MichaelsenAbstract:BACKGROUND Docosahexaenoic acid is present in high concentration in retina and does not influence Visual Development in preterm infants. It is still under discussion whether docosahexaenoic acid is important for Visual Development in term infants. METHODS Thirty-seven infants fed formula for a median of 14 days were randomized at median age of 25 days to three formulas: a) DHAGF: 0.3 wt% docosahexaenoic acid and 0.5 wt% gamma-linolenic acid; b) DHAF 0.3 wt% docosahexaenoic acid; or c) STF: standard formula without long-chain polyunsaturated fatty acids and 17 breast-fed infants were observed, using blood samples and anthropometric measurements from 1 to 4 months of age. At 4 months, Visual acuity was measured by swept steady-state Visual evoked potential. A cross-sectional study on 25 breast-fed infants was carried out as a reference group for the analyses. RESULTS Infants fed the two docosahexaenoic acid-supplemented formula had relative docosahexaenoic acid concentrations in red blood cell phospholipids almost as high as those in breast-fed infants, whereas infants in the standard formula group had significantly lower levels. The addition of gamma-linolenic acid to the formula had a positive effect on red blood cell arachidonic acid levels, compared with levels obtained using fish oil only. Visual acuity was significantly different among all feeding groups (analysis of variance; p = 0.05, means +/- standard deviation: breast-fed, 0.37+/-0.06 logMAR; DHAF and DHAGF combined, 0.40+/-0.07 logMAR; and standard formula 0.44+/-0.07 logMAR. However, there was no statistical difference among the formula groups. In a multiple regression analysis including all formula-fed infants, weight at delivery (p = 0.002), but not type of formula, was significantly associated with Visual acuity at 4 months of age. CONCLUSIONS The addition of docosahexaenoic acid resulted in concentrations in red blood cells at similar levels as those in breast-fed infants, whereas the increase in Visual acuity did not reach significance. The addition of gamma-linolenic acid resulted in higher arachidonic acid concentrations in red blood cells.
