Postprocessing of Structural En Face OCT Images of the Choroidal Haller Layer for Quantitative Assessment: An...

Background/Objectives: To develop a binarization workflow for structural en face OCT images of the choroidal Haller layer and examine how postprocessing parameters affect measurements, using chronological age as an exploratory reference. Methods: We included 66 healthy volunteers (66 eyes; 22-73 years; three age groups). En face Haller layer images from swept-source OCT angiography scans (DRI OCT Triton; 6 × 6 mm) were binarized using retinal vessel masking and Phansalkar thresholding. Radius R (22 values) and coefficients k and r (24 combinations) were varied. Results: Measurements depended strongly on R; age-group separation was similar over R = 13-26 pixels; permutation testing gave p = 0.031 across radii and p = 0.115 across all 45 configurations. Using the representative working configurations (R = 17 pixels; default k = 0.25 and r = 0.50), vessel density (VD), vessel length density (VLD), and inter-vessel distance (IVD) showed modest, non-monotonic nominal age-group differences (η² ≈ 0.10); those for VD and IVD were lost after accounting for masked regions. Adjusted for sex and spherical equivalent, VLD decreased and IVD increased with age, whereas VD did not. Conclusions: Measurements depend substantially on postprocessing parameters. The working configuration, selected and evaluated in one cohort, requires repeatability testing and independent validation.