Tracking-Based Interactive Assessment of Saccades, Pursuits, Visual Field, and Contrast Sensitivity in Children With Brain Injury

Visual deficits in children that result from brain injury, including cerebral/cortical visual impairment (CVI), are difficult to assess through conventional methods due to their frequent co-occurrence with cognitive and communicative disabilities. Such impairments hence often go undiagnosed or are only determined through subjective evaluations of gaze-based reactions to different forms, colors, and movements, which limits any potential for remediation. Here, we describe a novel approach to grading visual health based on eye movements and evidence from gaze-based tracking behaviors. Our approach—the “Visual Ladder”—reduces reliance on the user’s ability to attend and communicate. The Visual Ladder produces metrics that quantify spontaneous saccades and pursuits, assess visual field responsiveness, and grade spatial visual function from tracking responses to moving stimuli. We used the Ladder to assess fourteen hospitalized children aged 3 to 18 years with a diverse range of visual impairments and causes of brain injury. Four children were excluded from analysis due to incompatibility with the eye tracker (e.g., due to severe strabismus). The remaining ten children—including five non-verbal children—were tested multiple times over periods ranging from 2 weeks to 9 months, and all produced interpretable outcomes on at least three of the five visual tasks. The results suggest that our assessment tasks are viable in non-communicative children, provided their eyes can be tracked, and hence are promising tools for use in a larger clinical study. We highlight and discuss informative outcomes exhibited by each child, including directional biases in eye movements, pathological nystagmus, visual field asymmetries, and contrast sensitivity deficits. Our findings indicate that these methodologies will enable the rapid, objective classification and grading of visual impairments in children with CVI, including non-verbal children who are currently precluded from most vision assessments. This would provide a much-needed differential diagnostic and prognostic tool for CVI and other impairments of the visual system, both ocular and cerebral.

A Preliminary Study of the Relation of Visual Attention to Stimulus Complexity and Functional Vision in Individuals With Cortical Visual Impairment: Implications for Augmentative and Alternative Communication

Purpose Individuals with cortical visual impairment (CVI) can have difficulties with visual processing due to physical damage or atypical structures of visual pathways or visual processing centers in the brain. Many individuals with CVI have concomitant disabilities, including significant communication support needs; these individuals can benefit from augmentative and alternative communication (AAC). Because much AAC involves a visual channel, implementation of AAC must consider the unique visual processing skills and challenges in CVI. However, little is known empirically about how to best design AAC for individuals with CVI. This study examined processing of visual stimuli in four young adolescents with CVI. Method This study used a within-subjects experimental design that sought to provide an in-depth description of the visual engagement of individuals with CVI when viewing stimuli of various levels of complexity, either with or without a social cue. Results Participants engaged most with the simplest stimuli (relative to the size of those stimuli) and engaged more when a social cue was provided during the task. The level of engagement with more complex stimuli was related to participants' score on the CVI Range, a clinical assessment tool that characterizes level of visual functioning. Conclusions Implications for AAC include considerations for the internal complexity of AAC symbols and the complexity of the arrays created for individuals with CVI. Clinicians working with children with CVI who use AAC should consider the unique features of their visual processing.

Cortical Visual Impairment in Childhood: ‘Blindsight’ and the Sprague Effect Revisited

The paper discusses and provides support for diverse processes of brain plasticity in visual function after damage in infancy and childhood in comparison with injury that occurs in the adult brain. We provide support and description of neuroplastic mechanisms in childhood that do not seemingly exist in the same way in the adult brain. Examples include the ability to foster the development of thalamocortical connectivities that can circumvent the lesion and reach their cortical destination in the occipital cortex as the developing brain is more efficient in building new connections. Supporting this claim is the fact that in those with central visual field defects we can note that the extrastriatal visual connectivities are greater when a lesion occurs earlier in life as opposed to in the neurologically mature adult. The result is a significantly more optimized system of visual and spatial exploration within the ‘blind’ field of view. The discussion is provided within the context of “blindsight” and the “Sprague Effect”.

Delineating the genotypic and phenotypic spectrum of HECW2-related neurodevelopmental disorders

BackgroundVariants in HECW2 have recently been reported to cause a neurodevelopmental disorder with hypotonia, seizures and impaired language; however, only six variants have been reported and the clinical characteristics have only broadly been defined.MethodsMolecular and clinical data were collected from clinical and research cohorts. Massive parallel sequencing was performed and identified individuals with a HECW2-related neurodevelopmental disorder.ResultsWe identified 13 novel missense variants in HECW2 in 22 unpublished cases, of which 18 were confirmed to have a de novo variant. In addition, we reviewed the genotypes and phenotypes of previously reported and new cases with HECW2 variants (n=35 cases). All variants identified are missense, and the majority of likely pathogenic and pathogenic variants are located in or near the C-terminal HECT domain (88.2%). We identified several clustered variants and four recurrent variants (p.(Arg1191Gln);p.(Asn1199Lys);p.(Phe1327Ser);p.(Arg1330Trp)). Two variants, (p.(Arg1191Gln);p.(Arg1330Trp)), accounted for 22.9% and 20% of cases, respectively. Clinical characterisation suggests complete penetrance for hypotonia with or without spasticity (100%), developmental delay/intellectual disability (100%) and developmental language disorder (100%). Other common features are behavioural problems (88.9%), vision problems (83.9%), motor coordination/movement (75%) and gastrointestinal issues (70%). Seizures were present in 61.3% of individuals. Genotype-phenotype analysis shows that HECT domain variants are more frequently associated with cortical visual impairment and gastrointestinal issues. Seizures were only observed in individuals with variants in or near the HECT domain.ConclusionWe provide a comprehensive review and expansion of the genotypic and phenotypic spectrum of HECW2 disorders, aiding future molecular and clinical diagnosis and management.

Creating a Path for Systematic Investigation of Children With Cortical Visual Impairment Who Use Augmentative and Alternative Communication

Purpose There is limited information about how to support children with cortical visual impairment (CVI) who require augmentative and alternative communication (AAC). An initial review designed to explore the available evidence was used to outline critical needs in moving research and intervention forward for children who use AAC and have CVI. Method Previous systematic reviews, six databases, and theses and dissertations were systematically searched, along with reviews of the resulting works cited. An initial yield of 575 articles was narrowed to 10, which discussed AAC interventions that included children with CVI. Results Three interventions were technology based, and seven were instructional based. The use of textured microswitches was the most frequent form of technology intervention, with the frequency of switch activations being the most frequently coded outcome. Overall, the studies represent explorations in the area rather than systematic lines of inquiry. Conclusions While evidence shows at least some children with CVI have been included in AAC research to date, the inclusion is more incidental than deliberate. Issues such as clear descriptions of the vision capabilities and needs of participants may have impacted study results.