Eye-tracking saccade parameters reveal early cognitive decline in relation to Clinical Dementia Rating-Sum of Boxes scores

BackgroundVarious functional impairments in eye movements have been observed in Alzheimer's disease (AD) and other neurodegenerative disorders. Detecting abnormal eye movements may help identify individuals at risk of memory diseases even when evident clinical symptoms are absent.ObjectiveTo investigate the earliest possible stage at which the risk of memory impairment can be detected using computer-based eye-tracking (ET) analysis of King-Devick (KD) test performance.MethodsWe recruited a total of 34 healthy controls and 33 participants with a Clinical Dementia Rating-Sum of Boxes (CDR-SOB) score of 0.5 or higher. They all underwent a neurological examination, the Consortium to Establish a Registry for Alzheimer's Disease neuropsychological test battery (CERAD-NB), and a CDR interview. The KD reading test was performed using computer-based ET. We analyzed fixation durations, saccade durations, and saccade amplitudes. For this study, test results were analyzed in relation to CDR-SOB.ResultsThe mean duration of saccades was significantly shorter in the CDR-SOB 0.5 group compared to healthy controls (p = 0.001), and this difference remained significant across groups with CDR-SOB >0.5. The mean amplitude of saccades was significantly lower in individuals with CDR-SOB scores ranging from 1 to 4, as well as those with scores exceeding 4.5, in comparison to healthy controls (p = 0.007).ConclusionsThese findings suggest that ET analysis of the KD test may help detect individuals with very early cognitive problems. Therefore, this method shows promise as a supportive or potentially indicative biomarker for future studies aimed at developing user-friendly tools to identify individuals at risk for AD or other memory diseases.