Eye Dominance and Testing Order Effects in the Circularly-Oriented Macular Pigment Optical Density Measurements

Purpose: Psychophysical discrimination of structured light (SL) stimuli may be useful in screening for various macular disorders. The circularly-oriented macular pigment optical density (coMPOD), calculated from the discrimination performance of SL-induced entoptic phenomena, may reveal a novel functional biomarker of macular health. This study investigated the potential influence of eye dominance and testing order effects on SL-based stimulus perception, factors that potentially influence the sensitivity of screening tests based on SL technology. Methods: A psychophysical task was performed where various SL-based entoptic images with multiple azimuthal fringes rotating with a specific temporal frequency were projected onto the participants’ retinas (n = 28). By occluding the central areas of entoptic images, the retinal eccentricity R_T of the perceivable area of the stimuli was measured. The scale parameter of the coMPOD profile (α-value) was calculated for each participant using a spatiotemporal sensitivity model that takes into account the perceptual threshold measurements of SL stimuli with varying spatial densities and temporal frequencies. Results: The mean ± SD α-values for the dominant and non-dominant eyes were 0.11° ± 0.06° and 0.11° ± 0.05°, respectively. Similarly, the values for the first and second eyes were 0.11° ± 0.05° and 0.10° ± 0.05°, respectively. The Pearson correlation coefficient between eye dominance and testing order effects was r = 0.80 (p < 0.01). The Bland–Altman plots for both factors indicated zero bias. Conclusions: The results indicated repeatable measurements for both eyes, implying minimal impact from eye dominance and testing order on SL-based stimulus perception. The results provide a foundation for future studies exploring the clinical utility of SL tools in eye health.