Eye-Movement Intervention for Cognitive Impairment Across Schizophrenia Spectrum

Cognitive function will be assessed using the MATRICS Consensus Cognitive Battery (MCCB), a standardized neurocognitive battery widely used in schizophrenia research. The MCCB consists of nine subtests, including Trail Making Test, Symbol Coding, Hopkins Verbal Learning Test-Revised, Spatial Span, Neuropsychological Assessment Battery Mazes, Brief Visuospatial Memory Test-Revised (BVMT-R), Category Fluency Test, Continuous Performance Test-Identical Pairs, and Mayer-Salovey-Caruso Emotional Intelligence Test-Managing Emotions. The MCCB evaluates seven cognitive domains: speed of processing, attention/vigilance, working memory, verbal learning, visual learning, reasoning and problem solving, and social cognition. Particular attention will be given to the visual learning domain assessed by BVMT-R, which measures visuospatial memory. Changes in MCCB composite T-score, domain-specific T-scores, and BVMT-R performance from baseline to week 4 will be analyzed.

Fixation stability tasks will be used to assess participants' ability to maintain stable visual fixation under simple and distracted conditions. Participants will be instructed to keep their gaze on a black dot (0.5° in size) presented at the center of the screen while ignoring peripheral distractor stimuli ("*" mark, 0.5° in size). During the first 5 seconds of each trial, only the central target will be presented (simple fixation condition). During the subsequent 5-10 seconds, distractor stimuli will appear randomly around the target (distracted fixation condition), with varying locations (left/right) and eccentricities (near/far). A total of 10 trials will be conducted. Eye movement data will be recorded throughout the task. Outcome measures will include fixation duration and saccade count, reflecting fixation stability and the ability to suppress involuntary eye movements.

Antisaccade tasks will be used to assess oculomotor inhibitory control and executive regulation. Participants will first fixate on a central cross presented on a white screen. A peripheral target will then appear at different eccentricities, and participants will be instructed to suppress the reflexive saccade toward the target and generate a voluntary saccade toward the mirror position opposite to the target location. The task will include 30 antisaccade trials, with equal numbers of near- and far-target conditions. Outcome measures will include saccade latency, error rate, and saccade velocity, reflecting response initiation, inhibitory control, and oculomotor regulation.

Smooth pursuit tasks will be used to assess participants' ability to accurately track a moving visual target. Participants will be instructed to keep their heads motionless and follow a black dot presented on the screen using their eyes. The target will move according to predefined frequencies and trajectories. In the horizontal/vertical pursuit paradigm, the target will move horizontally and vertically with sinusoidal trajectories for 2.5 seconds each. In the Lissajous pursuit paradigm, the target will move simultaneously in horizontal and vertical directions using Lissajous trajectories with different frequencies and durations, including slow Lissajous pursuit (20 seconds) and fast Lissajous pursuit (10 seconds). Each trial will be repeated once. Outcome measures will include velocity gain, root mean square error (RMSE), and catch-up saccade count, reflecting pursuit accuracy, tracking precision, and compensatory eye movement responses.

Free-viewing tasks will be used to assess visual exploration patterns and attentional allocation. Participants will be instructed to freely view 35 static images, including natural landscapes, social scenes, objects, and abstract patterns. Each image will be presented for 10 seconds, with participants maintaining fixation on a central cross between image presentations. Eye movement parameters will be extracted during image viewing. Outcome measures will include fixation count, fixation duration, scan path length, and mean pupil diameter, reflecting visual exploration strategies and attentional allocation.

Psychosis-risk symptom severity will be assessed using the Structured Interview for Psychosis-Risk Syndromes (SIPS), with symptom severity quantified using the Scale of Psychosis-Risk Symptoms (SOPS) in clinical high-risk participants. The SOPS consists of 19 items across four domains: positive symptoms, negative symptoms, disorganized symptoms, and general symptoms. Each item is rated on a 7-point scale (0-6), with higher scores indicating greater symptom severity. The total SOPS score ranges from 0 to 114. Changes in total and domain-specific SOPS scores from baseline to week 4 will be evaluated.

Schizophrenia symptom severity will be assessed using the Positive and Negative Syndrome Scale (PANSS) in first-episode and chronic schizophrenia participants. The PANSS consists of 30 items grouped into three subscales: positive symptoms, negative symptoms, and general psychopathology. Each item is rated on a 7-point scale (1-7), with higher scores indicating greater symptom severity. The total PANSS score ranges from 30 to 210. Changes in total and subscale PANSS scores from baseline to week 4 will be evaluated.