Eye-tracking metrics during image viewing as possible biomarkers of cognitive alterations: A systematic review and meta-analysis in people with bipolar disorder

Eye-tracking metrics, such as fixation latency, fixation count, saccade amplitude, and gaze duration, are emerging digital biomarkers that can enhance our understanding of cognitive and emotional alterations in mental disorders. For bipolar disorder (BD), eye-tracking offers a promising approach to investigate the mechanisms underlying the deficits in attention, inhibitory control, and emotion processing. This meta-analysis examined the differences in eye-tracking metrics in individuals with BD compared to healthy controls (HCs) or individuals with other psychiatric conditions, while observing images with emotional or non-emotional content. A comprehensive search of the PubMed/MEDLINE, Scopus, and PsycINFO databases was conducted from inception to August 20, 2024. Studies investigating differences in eye-tracking metrics using an image viewing paradigm were reviewed, and meta-analyses were performed. Ten studies met the inclusion criteria: BD (n = 337) was compared to HCs (n = 352) in all ten studies, to major depressive disorder (n = 60) in two studies, and to schizophrenia (n = 22) in one study. Meta-analyses were only feasible for comparisons between BD and HCs. Individuals with BD exhibited higher latency for the first fixation, a reduced number of fixations, shorter gaze duration, and lower saccadic peak velocity and amplitude. Additionally, they showed shorter fixation durations only when viewing images with negative content. This report provides valuable insights into the cognitive and emotional difficulties faced by individuals with BD, which can guide the development of more targeted and effective assessments and interventions for this population.