Browsing by Author "McDowell N"

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Emulation of the subjective experience of visual dorsal stream dysfunction: a description of three in depth case studies
(Frontiers Media SA, 2025-01-06) St Clair Tracy H; McDowell N; Dutton GN; Ravenscroft J; Hay I; Blaikie A; Harpster K
These case studies explore the subjective visual experiences of individuals with cerebral visual impairment (CVI), specifically dorsal stream dysfunction (DSD) characterized by simultanagnosia. Through three in-depth case studies, this work documents the challenges these individuals face when navigating cluttered environments. The individuals were asked to describe their visual experiences while watching videos of varying complexity, with the future aim of creating a simulation of simultanagnosia. This process revealed a dynamic constriction of their attentional visual fields as scene complexity increased, and vice versa. Notably, the volunteers experienced a phenomenon where their vision could “get stuck” on specific items, with an apparent concurrent reduction in their ability to perceive and describe visual information as visual clutter increased. These consistent observations indicate that the symptoms of simultanagnosia are not simply limited to perceiving one or two objects at a time but can vary dynamically in response to environmental complexity. They enhance our understanding of how DSD impacts visual search and perceptual experiences, prompting us to propose the term “simultanagnostic vision” to describe this more nuanced and dynamic manifestation of CVI. The results are critical for developing effective interventions and optimizing support strategies for individuals affected by DSD, particularly children at sensitive developmental stages. Furthermore, we recommend deeper investigation into how different visual processing streams in the brain interconnect and influence each other, which may open new avenues for targeted therapeutic interventions.
Hiding in plain sight: children with visual perceptual difficulties in schools
(Frontiers Media S.A., 2024-11-27) McDowell N; St Clair Tracy H; Blaikie A; Ravenscroft J; Dutton GN; Bauer CM
Cerebral visual impairment (CVI) is increasingly being recognized as a significant cause of visual difficulties in children, particularly those with typical visual acuity, who nonetheless struggle in educational settings. This narrative review aims to elucidate the nature and impact of visual perceptual difficulties (VPD) associated with CVI in school-aged children, who often remain undiagnosed due to the current erroneous focus on visual acuity as a required diagnostic criterion for CVI. The review synthesizes findings from recent studies, highlighting that up to 3.4% of children in mainstream schools and a higher percentage in special educational settings may experience VPD, which significantly impacts upon their learning and development. The manifestations of VPDs, such as difficulties in motion perception, recognition, and visuospatial processing, are often subtle and can thus be overlooked, leading to misconceptions about the origins of the affected child’s abilities and behaviors. The review also discusses the challenges in current diagnostic processes, emphasizing the need for comprehensive history taking and assessments that go beyond standard visual acuity tests. It proposes a multi-faceted approach to identification and support, incorporating both clinical assessments and teacher/parental observations, to better address the needs of affected children. Furthermore, this paper advocates for the inclusion of VPDs in the International Classification of Diseases (ICD 11) to ensure children with these visual issues receive appropriate educational support. By integrating lived experiences of individuals with CVI and the latest research findings, this review underscores the urgent need for awareness and tailored educational strategies designed to support children with VPDs. The findings suggest that without such recognition and intervention, many children with VPDs will continue to “hide in plain sight,” facing unnecessary challenges in their educational and social development. The review concludes with recommendations for policy changes and future research directions to improve the identification, classification, and support of children with VPDs within the educational system.
Validation of the Austin Assessment: A screening tool for cerebral visual impairment related visual issues.
(Public Library of Science (PLoS), 2023-11-02) McDowell N; Butler P; Satgunam P
Cerebral visual impairment is the most common cause of vision impairment affecting children in the economically developed world with a prevalence rate of approximately 3.4%. Currently there are limited options for screening for cerebral visual impairment, resulting in many children going undiagnosed, especially those that have normal visual acuity. The aim of this research was to validate an iPad App called the Austin Assessment, which was developed as a potential screening tool for cerebral visual impairment related visual issues. The research involved three separate phases: (1) creating a database of normative ranges for children aged 5-18 across the different variables of the Austin Assessment, (2) using the Austin Assessment to screen children aged 5-13 to assess the effectiveness of the Austin Assessment as a screening tool for CVI related visual issues, and (3) conducting specific validation research assessing children using the Austin Assessment and an already validated visual search tool. Each phase used different quantitative research methodologies to help show the effectiveness of the Austin Assessment as a screening tool for cerebral visual impairment related visual issues. From phase one of the research, thresholds were established for three variables of the Austin Assessment for the age groupings of 5-8, 9-12 and 13-18. If a child meets one of these thresholds this indicates further assessment is required to determine if they do in fact have cerebral visual impairment related visual issues. Phase two identified 17 children out of 270 who had clinical findings indicating visual issues; potentially indicative of CVI; investigation into the nature of these visual issues is ongoing. Phase three found that the Austin Assessment has moderate diagnostic value for each age group, with good sensitivity and specificity, making it effective at distinguishing those children who have visual issues from those who have typical vision. Further investigation is needed to confirm this initial validation.
Vision-Based Assistive Technologies for People with Cerebral Visual Impairment: A Review and Focus Study
(Association for Computing Machinery, 2024-10-27) Gamage B; Holloway L; McDowell N; Do T-T; Price N; Lowery A; Marriott K
Over the past decade, considerable research has investigated Vision-Based Assistive Technologies (VBAT) to support people with vision impairments to understand and interact with their immediate environment using machine learning, computer vision, image enhancement, and/or augmented/virtual reality. However, this has almost totally overlooked a growing demographic: people with Cerebral Visual Impairment (CVI). Unlike ocular vision impairments, CVI arises from damage to the brain's visual processing centres. Through a scoping review, this paper reveals a signifcant research gap in addressing the needs of this demographic. Three focus studies involving 7 participants with CVI explored the challenges, current strategies, and opportunities for VBAT. We also discussed the assistive technology needs of people with CVI compared with ocular low vision. Our fndings highlight the opportunity for the Human-Computer Interaction and Assistive Technologies research community to explore and address this underrepresented domain, thereby enhancing the quality of life for people with CVI.
‘We don’t know nearly enough’: an online survey exploring perspectives of specialists who support children with brain-based visual impairments
(Frontiers Media S.A., 2025-01-29) Jakubowski JS; May E; Findlay R; McDowell N; Simkin SK; Hamm LM; Chang M
Introduction: Children with brain-based visual impairments (some of whom have a diagnosis of Cerebral Visual Impairment, or ‘CVI’) represent a growing and underserved population within vision services. These children often have more complex needs than those with ocular visual impairments and benefit from specialist support from multiple disciplines. This study aimed to understand the perspectives of these specialists in terms of their goals, views on collaboration, and understanding of the term ‘CVI’. Methods: We invited a range of specialists who work with children with brain-based visual impairments, including educators, rehabilitation staff, clinicians, and family members, to complete an online survey between April 2023 and April 2024. Results: The analysis included 94 respondents: 51 educators, 30 rehabilitation staff, 7 clinicians, and 6 family members. Respondents shared common goals of connecting with the child (87/94, 93%) and fostering their learning and development (82/94, 93%). However, respondents also noted some specific and divergent goals, which can be at odds with each other. Professional staff frequently identified family members as the most valuable source of information about their child’s vision (36/88, 41%), though family members expressed feeling under-valued. Transdisciplinary clinics were highlighted as a helpful model to provide quality child-centered care. Of the 73 professional staff who reported being familiar with the term ‘CVI’ (73/88, 83%), most (61/73, 84%) thought it was underdiagnosed, but respondents had different perspectives on what a diagnosis meant. Only 73% of professionals familiar with CVI reported receiving formal training about it. Discussion: The varied goals and different perspectives on CVI create challenges to providing cohesive support for children with brain-based visual impairments. Increasing the availability of complementary formal training across disciplines and adopting transdisciplinary models of care are promising approaches to improve the quality of services.