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Grading visual impairment in children with brain injury
Visual impairment in children due to brain injury -Cerebral Visual Impairment (CV)- is difficult to objectively assess because children at risk for CVI often lack the requisite verbal and cognitive skills to participate in standard visual assessment procedures. As a result, CVI is commonly diagnosed through subjective evaluations of a child’s gaze-derived reactions to different forms, colors and movements, which has limited insight into its pathophysiology and potential for remediation. Thus, there is a critical need to objectively quantify visual function after brain injury in children, and to characterize how visual impairment changes over time. This research project will evaluate the utility of novel tools we have developed to rapidly and objectively quantify visual function and diagnose CVI from eye movements in brain-injured children, independent of their ability to pay attention and communicate. The system uses a computer to display visual stimuli, and an eye tracking device to measure where a subject is looking. For spatial visual measures (i.e. acuity and contrast sensitivity) we smoothly move a visually interesting band-limited circular image on a computer screen, and an adaptive algorithm evaluates the extent to which the eyes move in concert with the image. When a child smoothly follows the image with their eyes for a few frames -which provides objective evidence that they can see it- stimulus features are changed in real-time to a higher spatial frequency (for acuity) or lower contrast (for contrast sensitivity) until they can no longer follow, which quantifies the limit of their ability in seconds. A variant of the methodology is also able to rapidly quantify gaze diagnostics, such as the velocity, latency and spatial precision of eye movements. Together, these methodologies are able to objectively classify and grade CVI based on visual measures that are rooted in the known physiology of the visual system, and are widely used to evaluate other visual diseases. Our goal in this study is to validate the feasibility of our new approach as a differential diagnostic and prognostic tool for CVI. For this we will evaluate our new gaze-based measures against widely used clinical assessments, to identify and grade visual impairment in children hospitalized for brain injury, and repeat the measures longitudinally. We expect that our approach will be able to identify and grade CVI in many brain-injured children better than current clinical procedures, and better predict the probable course of visual recovery. This evidence-based approach is expected to set the stage for future clinical studies aimed at objectively evaluating the efficacy of therapeutic interventions for CVI.