Effects of Fingolimod Therapy on Choroidal Vascularity Index in Patients with Relapsing–Remitting Multiple Sclerosis: A Retrospective Longitudinal Study

PURPOSE: To evaluate the longitudinal effects of fingolimod therapy on choroidal vascular architecture, particularly the choroidal vascularity index (CVI), in patients with relapsing-remitting multiple sclerosis (RRMS). METHODS: This retrospective study included 51 RRMS patients who initiated fingolimod therapy and were followed for a median of 24 months (range 12-36 months). 51 age- and sex-matched healthy individuals served as a cross-sectional reference group. Central macular thickness (CMT), retinal nerve fibre layer (RNFL) thickness, subfoveal choroidal thickness (SFCT), choroidal luminal area (LA), stromal area (SA), total choroidal area (TCA), and CVI were assessed at baseline and end of follow-up using spectral-domain OCT with enhanced depth imaging. Spearman correlation analysis was performed between treatment duration and the magnitude of change in CVI and SA. RESULTS: CMT, SFCT, RNFL, LA, and TCA remained stable throughout follow-up (all p > 0.05). SA decreased significantly (p = 0.007) and CVI increased significantly (0.6968 ± 0.0287 → 0.7082 ± 0.0321; mean paired difference +0.0114, 95% CI 0.0040-0.0188; p = 0.003). Follow-up CVI was significantly higher in patients than in healthy controls (p = 0.017). No patient developed macular oedema. A moderate positive correlation was found between treatment duration and ΔCVI (ρ = 0.38, p = 0.006).No correction for multiple comparisons was applied; all findings are exploratory. CONCLUSION: Fingolimod does not affect conventional OCT parameters in RRMS patients. A statistically significant increase in CVI accompanied by stromal reduction, correlating modestly with treatment duration, suggests a progressive change in choroidal vascular-stromal balance associated with treatment duration. These are exploratory findings; prospective studies with untreated RRMS comparators, longitudinal control data, and functional visual endpoints are required before drawing causal conclusions.