Evaluating the reliability of structured light entoptic tasks

Human perception of polarised light, known as Haidinger's brushes, is linked to macular health but is typically too faint for reliable clinical use. Structured light can enhance these entoptic patterns, but the test-retest reliability of this approach requires validation. Here, we evaluated the reliability of a structured light-based psychophysical task in twenty-five participants (fifty eyes) across two sessions separated by one to fourteen days. Participants viewed structured light stimuli that produced rotating entoptic patterns and identified the rotation direction in a two-alternative forced-choice paradigm while a central obstruction varied in size to determine retinal eccentricity thresholds. Intraclass correlation coefficients demonstrated good to excellent reliability, with values of 0.83 for right eyes and 0.93 for left eyes. Bland-Altman analysis revealed non-significant mean differences of -0.32 degrees and - 0.12 degrees for right and left eyes, respectively, with limits of agreement spanning approximately 6° and 4° around mean thresholds of ~ 6.1° and ~ 6.5°, confirming an absence of systematic bias. These findings indicate that structured light-based psychophysical tasks can yield repeatable measurements of entoptic pattern extent in healthy individuals. Further validation in clinical populations and older age groups is required before the method can be recommended for clinical screening.