Validity and reliability of eye tracking for visual acuity assessment in children with cortical visual impairment

"It's like a guessing game all the time": parent insights on barriers, supports, and priorities for children with cortical visual impairment and complex communication needs

Parents of children with both cortical visual impairment (CVI) and complex communication needs offer unique perspectives on their children's journeys to receiving proper diagnoses, supports, and interventions, such as augmentative and alternative communication (AAC). This study explored the lived experiences, supports, and barriers identified by parents through a qualitative phenomenological approach. Nine parents of children with both CVI and complex communication needs were interviewed virtually. Results indicated five themes descriptive of the parents' experiences: Challenges Piecing Together a CVI Diagnosis; Dealing with Low Expectations of Others; Parents Empowered to Take Action; Guessing Game to Determine Appropriate AAC to Accommodate CVI; and Aligning Professional Practice with Parent Priorities. Whereas some of these themes echoed the experiences of parents of children with complex communication needs (such as those with cerebral palsy) who were not specifically diagnosed with CVI, other themes were unique to this set of parents including the uncertainty of AAC design and intervention given the challenges of CVI and the necessity of more than one way for children to communicate given their visual challenges. This study highlighted the dire need for continued investigation to determine effective AAC interventions for individuals with CVI.

A review of experimental task design in psychophysical eye tracking research

While eye tracking is a technique commonly used in the experimental study of higher-level perceptual processes such as visual search, working memory, reading, and scene exploration, its use for the quantification of basic visual functions (visual acuity, contrast sensitivity, color vision, motion detection) is less explored. The use of eye movement features as dependent variables in a psychophysical investigation can serve multiple roles. They can be central in studies with neurological patients or infants that cannot comply with verbal instructions, understand task demands, and/or emit manual responses. The technique may also serve a complementary role, determining the conditions under which a manual or verbal response is given, such as stimulus position in the visual field, or it can afford the analysis of new dependent variables, such as the time interval between oculomotor and manual responses. Our objective is to review the literature that applied the eye tracking technique to psychophysical problems. The two questions our review raises are: can eye movements (reflex or voluntary) be an objective index of stimulus detection in psychophysical tasks? If so, under what conditions, and how does it compare with traditional paradigms requiring manual responses? Our (non-systematic) methodological review selected studies that used video-oculography as the technique of choice and had a basic visual function as their primary object of investigation. Studies satisfying those criteria were then categorized into four broad classes reflecting their main research interest: (1) stimulus detection and threshold estimation, (2) the effects of stimulus properties on fixational eye movements, (3) the effects of eye movements on perception, and (4) visual field assessment. The reviewed studies support the idea that eye tracking is a valuable technique for the study of basic perceptual processes. We discuss methodological characteristics within each of the proposed classification area, with the objective of informing future task design.

Validity and reliability of CVI Range assessment for Clinical Research (CVI Range-CR): a longitudinal cohort study

Introduction

Cortical visual impairment (CVI) is the leading cause of paediatric visual impairment in developed countries. Children with CVI exhibit visual behaviours that differ from those with ocular causes of visual impairment. Currently, there is no standard method of assessing these visual characteristics. We have developed a modified version of the CVI Range, a functional vision assessment, suitable for use in clinical research (CVI Range–Clinical Research (CVI Range-CR)). The purpose of this study is to assess the reliability and validity of this instrument in children with CVI.

Methods and analysis

This is a prospective cohort study of 45 children with CVI. A neuro-ophthalmologist will grade visual acuity using the six-level Visual Behaviour Scale (VBS). A neuropsychologist will administer the CVI Range-CR, which will be recorded. The neuropsychologist and two external graders will review and score recorded assessments. These procedures will be performed at baseline and 12 months. We will calculate the intraclass correlation coefficient to assess inter-rater reliability at baseline and follow-up. Additionally, we will correlate CVI Range-CR scores to VBS scores.

Assessing Higher-Order Visual Processing in Cerebral Visual Impairment Using Naturalistic Virtual-Reality-Based Visual Search Tasks

Cerebral visual impairment (CVI) is a brain-based disorder associated with the maldevelopment of central visual pathways. Individuals with CVI often report difficulties with daily visual search tasks such as finding a favorite toy or familiar person in cluttered and crowded scenes. We developed two novel virtual reality (VR)-based visual search tasks combined with eye tracking to objectively assess higher order processing abilities in CVI. The first (virtual toybox) simulates a static object search, while the second (virtual hallway) represents a dynamic human search task. Participants were instructed to search for a preselected target while task demand was manipulated with respect to the presence of surrounding distractors. We found that CVI participants (when compared to age-matched controls) showed an overall impairment with visual search on both tasks and with respect to all gaze metrics. Furthermore, CVI participants showed a trend of worsening performance with increasing task demand. Finally, search performance was also impaired in CVI participants with normal/near normal visual acuity, suggesting that reduced stimulus visibility alone does not account for these observations. This novel approach may have important clinical utility in helping to assess environmental factors related to functional visual processing difficulties observed in CVI.

The Multidisciplinary Guidelines for Diagnosis and Referral in Cerebral Visual Impairment

Introduction

Cerebral visual impairment (CVI) is an important cause of visual impairment in western countries. Perinatal hypoxic-ischemic damage is the most frequent cause of CVI but CVI can also be the result of a genetic disorder. The majority of children with CVI have cerebral palsy and/or developmental delay. Early diagnosis is crucial; however, there is a need for consensus on evidence based diagnostic tools and referral criteria. The aim of this study is to develop guidelines for diagnosis and referral in CVI according to the grade method.

Patients and Methods

We developed the guidelines according to the GRADE method 5 searches on CVI (children, developmental age ≤ 18 years) were performed in the databases Medline, Embase, and Psychinfo, each with a distinct topic.

Results

Based on evidence articles were selected on five topics: 1. Medical history and CVI-questionnaires 23 (out of 1,007). 2. Ophthalmological and orthoptic assessment 37 (out of 816). 3. Neuropsychological assessment 5 (out of 716). 4. Neuroradiological evaluation and magnetic resonance imaging (MRI) 9 (out of 723). 5. Genetic assessment 5 (out of 458).

Conclusion

In medical history taking, prematurity low birth weight and APGAR (Appearance, Pulse, Grimace, Activity, Respiration) Scores (<5) are important. Different questionnaires are advised for children under the age of 3 years, older children and for specific risk groups (extremely preterm). In ophthalmological examination, eye movements, specially saccades, accommodation, crowding, contrast sensitivity and visual fields should be evaluated. OCT can show objective signs of trans-synaptic degeneration and abnormalities in fixation and saccades can be measured with eye tracking. Screening of visual perceptive functioning is recommended and can be directive for further assessment. MRI findings in CVI in Cerebral Palsy can be structured in five groups: Brain maldevelopment, white and gray matter lesions, postnatal lesions and a normal MRI. In children with CVI and periventricular leukomalacia, brain lesion severity correlates with visual function impairment. A differentiation can be made between cortical and subcortical damage and related visual function impairment. Additional assessments (neurological or genetic) can be necessary to complete the diagnosis of CVI and/or to reveal the etiology.