Association Between PS-OCT Derived Polarimetric Entropy and RPE Cellular Metrics Measured With Adaptive Optics Imaging in Retinitis Pigmentosa

Purpose: The purpose of this study was to investigate the association between entropy values derived from the retinal pigment epithelium (RPE) layer using polarization-sensitive optical coherence tomography (PS-OCT) and RPE cellular metrics obtained by adaptive optics transscleral flood illumination (AO-TFI), including cell density, spacing, regularity, and dispersion. We further aimed to determine which cellular structural alterations in retinitis pigmentosa (RP) are reflected by entropy. Methods: Healthy controls and patients with RP who underwent both PS-OCT and AO-TFI imaging were included. Spearman correlation coefficients were calculated to assess the relationships between polarimetric entropy in PS-OCT and each AO-TFI-derived parameter. To account for repeated measurements within the same eye and the effects of group and eccentricity, linear mixed-effects models were constructed to evaluate the independent associations between entropy and AO-TFI metrics after adjustment for these factors. Results: Polarimetric entropy showed the strongest positive correlation with RPE cell density among the AO-TFI parameters and was negatively correlated with spacing of RPE cells. No clear associations were observed with regularity or dispersion. In linear mixed-effects models, the association between entropy and RPE cell density differed between groups, with a significant association observed in the RP group but not in healthy controls. Conclusions: PS-OCT-derived polarimetric entropy was associated with RPE cell density measured by AO-TFI, with the association primarily observed in RP rather than in healthy controls. These findings suggest that correspondence between the two imaging modalities may contribute to quantitative assessment of outer retinal-RPE complex alterations and has potential utility as a biomarker in retinal degenerative diseases.