Structural and Vascular Characteristics of PHOMS in Pediatric Pseudopapilledema Running Title: PHOMS in Pediatric Pseudopapilledema

Purpose To evaluate the structural and vascular characteristics of peripapillary hyperreflective ovoid mass-like structures (PHOMS) in pediatric pseudopapilledema and to investigate their relationship with retinal nerve fiber layer (RNFL) thickness and optic nerve head parameters. Methods This retrospective study included 38 pediatric patients with pseudopapilledema (with or without optic disc drusen [ODD]) and 36 age- and sex-matched healthy controls. Structural optical coherence tomography (OCT) and OCT angiography (OCTA) parameters were analyzed, including global and sectoral RNFL thickness, ganglion cell complex (GCC) metrics, Bruch’s membrane opening (BMO) diameter, choroidal vascularity index (CVI), radial peripapillary capillary (RPC) density, and macular vascular parameters. In PHOMS-positive eyes, maximum PHOMS diameter was measured on enhanced depth imaging OCT. Group comparisons were performed using generalized estimating equations. Correlation and regression analyses were conducted to evaluate associations between PHOMS size and structural or vascular parameters. Results In single-eye analysis, PHOMS-positive eyes (n = 23) demonstrated significantly higher global RNFL thickness compared with controls (p = 0.018). No significant differences were observed in spherical equivalent, BMO diameter, optic disc area, GCC thickness, CVI, or OCTA-derived vascular parameters (all p > 0.05). Maximum PHOMS diameter showed a significant positive correlation with global RNFL thickness (r = 0.526, p = 0.010) and remained independently associated in multivariable regression analysis (β = 0.44, p = 0.044). In eye-level analyses including ODD-positive, ODD-negative, and healthy eyes, RNFL thickness differed significantly among groups (p < 0.001), whereas no consistent differences were observed in vascular or ganglion cell parameters. Conclusions In pediatric pseudopapilledema, PHOMS are associated with increased RNFL thickness, and PHOMS size independently predicts RNFL variation. The absence of consistent vascular or ganglion cell alterations suggests that PHOMS predominantly represent a structural optic nerve head phenotype rather than a generalized microvascular disorder. Recognition of this pattern may aid in differentiating benign structural variants from early optic neuropathy in children.