Quantitative optical property mapping of the periocular region using spatial frequency domain imaging

Noninvasive characterization of periocular skin optical properties is critical for understanding tissue alterations associated with thyroid eye disease and other orbital adnexal pathologies. Spatial frequency domain imaging (SFDI) provides quantitative, in vivo assessment of tissue absorption and scattering, making it a promising tool for clinical evaluation of the periocular region. However, the complex curvature and height variations of orbital anatomy pose unique challenges that may affect measurement accuracy and reproducibility. This study evaluates the feasibility and repeatability of SFDI for periocular imaging in healthy subjects, establishing a foundation for future investigations of disease-related tissue changes.

The study aims to establish normative SFDI-derived optical properties of periocular skin in the absence of cutaneous disease.

Twenty-five healthy participants were imaged using the Reflect RS™ SFDI system. Reduced scattering ( ${\mu }_s^{\text{'}}$ ) and absorption ( ${\mu }_a$ ) coefficients were quantified for predefined regions of interest (ROI): inferior temporal, inferior nasal, and forehead (control). A subset of seven subjects underwent imaging in both frontal and lateral orientations to evaluate the effect of acquisition angle.

Normative ranges for ${\mu }_s^{\text{'}}$ and ${\mu }_a$ across periocular and forehead ROIs are reported. Imaging angle did not significantly affect optical property estimates. Across the cohort, ${\mu }_a$ increased and ${\mu }_s^{\text{'}}$ decreased with higher Fitzpatrick scores, consistent with prior literature. We observed that laterality and ROI appear to be significant when measuring optical properties. In addition, ${\mu }_s^{\text{'}}$ suggests a potential stepwise decline with advancing age.

This study provides the first quantitative characterization of normal periocular skin using SFDI across diverse skin types. Measurements were robust to acquisition angle but varied with pigmentation, underscoring the need to account for Fitzpatrick scores in clinical applications. Establishing normative data is essential for future studies involving periocular disease.