The Role of Vitamin D and Gender in Optic Neuritis

Background: Optic neuritis (ON) is a common manifestation of demyelinating disease. The optic nerve can serve as a model of the central nervous system, allowing for evaluation of inflammation and degeneration using optical coherence tomography (OCT) to measure retinal nerve fiber layer (RNFL) thickness and other afferent pathway markers. Vitamin D insufficiency is a risk factor for multiple sclerosis and ameliorates inflammation.  Assessment of vitamin D status in ON may support a neuroprotective role.

Objectives: We hypothesize that vitamin D sufficiency (25(OH)D > 80 nmol/L) is associated with better OCT outcomes and axonal preservation/recovery after ON. Outcomes include RNFL, ganglion cell layer (GCL) thickness and inter-eye difference (IED) in both at 6 months and baseline between vitamin D sufficient and insufficient groups.

Methods: In this prospective cohort study, patients with acute ON <= 30 days undergo OCT to assess RNFL GCL, macular volume (MV), and serum 25(OH)D testing at baseline and month 6.  Additional vision metrics and EDSS testing are also performed at these times.

Results: Presently, 49 patients have been enrolled (36F/13M) and 42 have completed the study.  At baseline, 68% of patients were vitamin D insufficient, which was associated with greater mean baseline edema in RNFL (131 vs 106 µm, p=0.14) and MV (10.2 vs 9.8 mm³, p=0.036).  At month 6, while RNFL edema persisted, mean GCL IED was greater in vitamin D insufficient patients (14 vs 7 µm, p=0.094).  Regardless of baseline RNFL or vitamin D, men had significantly lower 6 month mean RNFL (70 vs 81 µm, p=0.025) and greater IED in both mean RNFL and GCL (both 21 vs 8 µm, p=0.005 and p=0.004 respectively) versus women.

Conclusions: Optical coherence tomography demonstrates that in acute ON, vitamin D insufficiency is associated with greater edema, in keeping with its known anti-inflammatory actions.  At month 6, vitamin D insufficiency and male gender are both risk factors for poorer OCT outcomes (such as GCL thinning), suggesting that both vitamin D status and female gender, possibly acting together, may confer neuroprotection and/or improved repair in the optic nerve after an ON event.