Abstract
PURPOSE: To longitudinally characterize structural and vascular density changes in demyelinating optic neuritis (DON) using spectral-domain optical coherence tomography (OCT) and OCT angiography (OCTA). METHODS: This prospective study included 23 patients (mean age 41.1 ± 15.3 years; 75.9% female) with first unilateral DON at a Portuguese tertiary center. Baseline (T0) and 6-month (T6) assessments included best-corrected visual acuity (BCVA), peripapillary retinal nerve fiber layer (pRNFL), ganglion cell complex (GCC), focal loss volume (FLV), global loss volume (GLV), and vessel densities from the radial peripapillary capillary (RPC) and macular superficial vascular plexus (SVP). Affected and fellow eyes were compared. The Wilcoxon test was applied, and p-values were adjusted using the Benjamini-Hochberg method (p < 0.05). RESULTS: At baseline, affected eyes showed increased pRNFL thickness compared with fellow eyes, particularly in nasal sectors including nasal, inferonasal, nasal-upper, and nasal-lower regions (p ≤ 0.024). At 6 months, significant thinning was detected in average pRNFL and temporal quadrant (both p = 0.036), accompanied by higher FLV and GLV values (p ≤ 0.036). Longitudinally (T0-T6), progressive thinning occurred across all quadrants and ONH sectors in affected eyes (p < 0.05), while fellow eyes remained stable. OCTA revealed reduced vessel density in whole-image all-vessels, as well as in superior and inferior peripapillary sectors (p ≤ 0.028) at T6, with no significant longitudinal change after correction. CONCLUSION: Demyelinating optic neuritis exhibits a dynamic course with early structural thickening followed by progressive neuroaxonal loss. Significant longitudinal pRNFL and ONH thinning supports sustained axonal degeneration beyond the acute phase. OCTA changes were restricted to selected peripapillary sectors, suggesting subtle parallel microvascular alterations. OCT and OCTA offer complementary information for comprehensive assessment and monitoring of demyelinating optic neuropathies.