: The purpose of this study is to investigate alterations in optical coherence tomography (OCT) and OCT angiography (OCT-A) parameters in patients with pediatric-onset multiple sclerosis (POMS). This prospective cross-sectional study included 37 POMS patients and 36 healthy controls (HCs). We performed OCT and OCT-A scans. POMS eyes were categorized into two subgroups: those with a history of optic neuritis (MS + ON) and those without (MS-ON). The mean ages of the POMS patients and HCs were 15.8 ± 0.2 and 14.7 ± 2.5 years, respectively (p = 0.266). Compared with that in HCs, the retinal nerve fiber layer (RNFL) thickness in MS + ON eyes was lower in three segments; it was significantly lower only in the temporal segment in MS-ON eyes. In all quadrants, except one, ganglion cell-inner plexiform layer (GC-IPL) thicknesses were significantly thinner in MS + ON and MS-ON eyes than in HCs. In multiple quadrants, vessel density (VD) in the radial peripapillary capillary (RPC) plexus was significantly lower in MS + ON eyes than in MS-ON and HCs. Compared with those of MS-ON and HCs, the whole and perifoveal VDs in the superficial capillary plexus (SCP) of MS + ON eyes were significantly lower. VD in the deep capillary plexus (DCP) and foveal avascular zone (FAZ) did not differ between groups. Conclusions: The OCT-A findings in POMS patients include a reduction in vessel density in the macula and peripapillary area in the setting of optic neuritis. The thinning of the GC-IPL and RNFL was observed in POMS eyes irrespective of prior ON history, but ON was associated with more prominent thinning.

Background: • On the basis of the reported clinical association between the MS course and retinal dysfunction, quantitative retinal vessel measurements may be potential markers for MS. • The literature shows that the majority of OCT and OCT-A studies were in adult MS patients, with a limited number of studies in children. Background: • In this study, we present 37 POMS patients, identify clinically silent retinal nerve fiber and ganglion cell loss independent of optic neuritis, and demonstrate a reduction in vessel density in the macula and peripapillary area in the setting of optic neuritis. • The inclusion of very early cases of MS, such as the pediatric group, may offer a unique opportunity to better understand the impact of retinal vascular changes on disease pathogenesis.