Retinal and Choroidal Microvascular Alterations Associated with Compensatory Head Tilt in Congenital Superior Oblique Palsy: An Interocular OCTA Analysis.

Background/Objectives: To evaluate interocular retinal and choroidal microvascular alterations associated with compensatory head tilt in unilateral congenital superior oblique palsy (SOP) and to investigate their relationship with head tilt degree using optical coherence tomography angiography (OCTA). Methods: This retrospective cross-sectional study included 34 patients with congenital SOP and head tilt-dominant abnormal head posture. A paired-eye design compared the tilt-side eye with the opposite-side eye. Superficial and deep capillary plexus (SCP, DCP) vessel density, foveal avascular zone (FAZ) parameters, choroidal vascularity index (CVI), and subfoveal choroidal thickness (SFCT) were assessed. Interocular differences were defined as Δ = opposite-side eye - tilt-side eye. Correlation and multivariable regression analyses were performed to assess associations with head tilt degree. The interocular difference in CVI (ΔCVI) and its association with head tilt degree were defined as the primary outcomes, whereas retinal OCTA parameters, FAZ metrics, and SFCT were considered exploratory secondary outcomes. Results: CVI showed the most prominent interocular difference, being higher in the opposite-side eye than in the tilt-side eye (0.71 ± 0.04 vs. 0.68 ± 0.04; p < 0.001), whereas SFCT did not differ significantly (p = 0.395). SCP foveal vessel density and DCP inferior vessel density showed nominal differences in the unadjusted analyses but did not remain statistically significant after Benjamini-Hochberg false discovery rate correction. ΔCVI correlated positively with head tilt degree (ρ = +0.533, p = 0.001) and remained independently associated in multivariable analysis (p = 0.001). Conclusions: Compensatory head tilt in congenital SOP is associated with measurable interocular microvascular asymmetry, predominantly at the choroidal level. CVI demonstrated the strongest association with head tilt severity, whereas retinal OCTA findings were exploratory, suggesting that OCTA may provide objective insight into posture-related choroidal microvascular alterations.