Eye-Tracking as a Diagnostic Tool for Dyslexia ADHD Stroke and Alzheimer’s Using Average Fixation Duration Metrics

Average Fixation Duration (AFD), a central metric in eye-tracking analytics, quantifies the time a viewer’s gaze remains on a fixed point. This study investigates AFD as a multidisciplinary biomarker of cognitive and motor function across three key populations: children with developmental dyslexia, adults with acquired dyslexia following stroke, and individuals diagnosed with Alzheimer’s disease. Using a combination of case studies, published datasets, and Excel-based computational models, we examine how prolonged fixation durations signal increased cognitive effort, impaired gaze transitions, or neurodegenerative disruption. In dyslexic children, elevated AFD values during reading tasks correspond to decoding struggles and increased processing load. For stroke survivors, AFD reflects impaired saccadic control and hemispheric neglect, particularly on contralesional visual targets. In Alzheimer’s patients, prolonged fixations indicate diminished attentional focus and degraded motor-planning circuits. AFD thresholds are proposed for clinical interpretation across age and condition. Two longitudinal case studies show post-therapy improvements in AFD values following phonics-based and visual-scanning interventions. These findings support the integration of AFD metrics into cognitive diagnostics and rehabilitation monitoring systems. By translating eye-tracking outputs into actionable insights, AFD enables more responsive, data-driven support for learning, recovery, and neurocognitive assessment.