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Understanding low functioning cerebral visual impairment: An Indian context.

ABSTRACT: For several reasons, cerebral visual impairment (CVI) is emerging as a major cause of visual impairment among children in the developing world and we are seeing an increasing number of such children in our clinics. Owing to lack of early training about CVI and it being a habilitation orientated subject, we need to become equipped to optimally help the affected children. In this paper we have explained our pragmatic approach in addressing children who present with low functioning CVI. Initially we explain briefly, how vision is processed in the brain. We then present what should be specifically looked for in these children in regular clinics as a part of their comprehensive ophthalmic examination. We discuss the process of functional vision evaluation that we follow with the help of videos to explain the procedures, examples of how to convey the conclusions to the family, and how to use our findings to develop intervention guidelines for the child. We explain the difference between passive vision stimulation and vision intervention, provide some common interventions that may be applicable to many children and suggest how to infuse interventions in daily routines of children so that they become relevant and meaningful leading to effective learning experiences.

SUBMITTER: Pehere NK

PROVIDER: S-EPMC6786190 | biostudies-literature | 2019 Oct

REPOSITORIES: biostudies-literature

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Understanding low functioning cerebral visual impairment: An Indian context.

Pehere Niranjan K NK Jacob Namita N

Indian journal of ophthalmology 20191001 10

For several reasons, cerebral visual impairment (CVI) is emerging as a major cause of visual impairment among children in the developing world and we are seeing an increasing number of such children in our clinics. Owing to lack of early training about CVI and it being a habilitation orientated subject, we need to become equipped to optimally help the affected children. In this paper we have explained our pragmatic approach in addressing children who present with low functioning CVI. Initially w ...[more]

PMID: 31546476

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Project description:BackgroundTo gain more insight into genetic causes of cerebral visual impairment (CVI) in children and to compare ophthalmological findings between genetic and acquired forms of CVI.MethodsThe clinical data of 309 individuals (mainly children) with CVI, and a visual acuity ? 0.3 were analyzed for etiology and ocular variables. A differentiation was made between acquired and genetic causes. However, in persons with West syndrome or hydrocephalus, it might be impossible to unravel whether CVI is caused by the seizure disorder or increased intracranial pressure or by the underlying disorder (that in itself can be acquired or genetic). In two subgroups, individuals with 'purely' acquired CVI and with 'purely' genetic CVI, the ocular variables (such as strabismus, pale optic disc and visual field defects) were compared.ResultsIt was possible to identify a putative cause for CVI in 60% (184/309) of the cohort. In the remaining 40% the etiology could not be determined. A 'purely' acquired cause was identified in 80 of the patients (26%). West syndrome and/or hydrocephalus was identified in 21 patients (7%), and in 17 patients (6%) both an acquired cause and West and/or hydrocephalus was present. In 66 patients (21%) a genetic diagnosis was obtained, of which 38 (12%) had other possible risk factor (acquired, preterm birth, West syndrome or hydrocephalus), making differentiation between acquired and genetic not possible. In the remaining 28 patients (9%) a 'purely' genetic cause was identified.CVI was identified for the first time in several genetic syndromes, such as ATR-X, Mowat-Wilson, and Pitt Hopkins syndrome. In the subgroup with 'purely' acquired causes (N = 80) strabismus (88% versus 64%), pale optic discs (65% versus 27%) and visual field defects (72% versus 30%) could be observed more frequent than in the subgroup with 'purely' genetic disorders (N = 28).ConclusionsWe conclude that CVI can be part of a genetic syndrome and that abnormal ocular findings are present more frequently in acquired forms of CVI.

Project description:Visuospatial processing deficits are commonly observed in individuals with cerebral visual impairment, even in cases where visual acuity and visual field functions are intact. Cerebral visual impairment is a brain-based visual disorder associated with the maldevelopment of central visual pathways and structures. However, the neurophysiological basis underlying higher-order perceptual impairments in this condition has not been clearly identified, which in turn poses limits on developing rehabilitative interventions. Using combined eye tracking and EEG recordings, we assessed the profile and performance of visual search on a naturalistic virtual reality-based task. Participants with cerebral visual impairment and controls with neurotypical development were instructed to search, locate and fixate on a specific target placed among surrounding distractors at two levels of task difficulty. We analysed evoked (phase-locked) and induced (non-phase-locked) components of broadband (4-55 Hz) neural oscillations to uncover the neurophysiological basis of visuospatial processing. We found that visual search performance in cerebral visual impairment was impaired compared to controls (as indexed by outcomes of success rate, reaction time and gaze error). Analysis of neural oscillations revealed markedly reduced early-onset evoked theta [4-6 Hz] activity (within 0.5 s) regardless of task difficulty. Moreover, while induced alpha activity increased with task difficulty in controls, this modulation was absent in the cerebral visual impairment group identifying a potential neural correlate related to deficits with visual search and distractor suppression. Finally, cerebral visual impairment participants also showed a sustained induced gamma response [30-45 Hz]. We conclude that impaired visual search performance in cerebral visual impairment is associated with substantial alterations across a wide range of neural oscillation frequencies. This includes both evoked and induced components suggesting the involvement of feedforward and feedback processing as well as local and distributed levels of neural processing.

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Understanding low functioning cerebral visual impairment: An Indian context.

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Understanding low functioning cerebral visual impairment: An Indian context.

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