Association of vitamin D deficiency with RNFL thickness in MS individuals without history of optic neuritis

Vitamin D deficiency has been associated with both increased risk and severity of Multiple Sclerosis (MS) as it has a modulating effect on the immune process that causes inflammation/demyelination and axonal damage. Optical Coherence Tomography (OCT) offers a quick, reliable and non-invasive way to assess the Retinal Nerve Fiber Layer (RNFL) and identifies axonal loss generated by either direct inflammation or from neurodegeneration. Objective: To determine the association of vitamin D and RNFL in MS patients without a history of Optic Neuritis (ON) by comparing RNFL thickness in patients that are vitamin D deficient with those having normal serum levels. Method: The cohort of 76 MS patients underwent OCT testing to assess the RNFL thickness and macular volume, and measurement of serum 25-OH Vitamin D level. Vitamin D deficiency was defined as <30 ng/ml and sufficiency as >= 30 ng/ml. Results: A total of 131 eyes were divided in two groups: vitamin D deficient (n=86 eyes, mean=17.7 ng/ml) and vitamin D sufficient (n=45 eyes, mean=40.3 ng/ml). Twenty one eyes had previous ON and were excluded from this analysis. Vitamin D deficiency was identified in 66% of the participants. RNFL thickness was similar for the vitamin D deficient and sufficient groups (85.5 vs 86 mu m respectively, p=0.89). Significant differences were present for age with the deficient group being younger (42 years vs 51 years, p=0.005) and having shorter disease duration (7.5 years vs 11.4 years, p=0.006). Conclusion: Vitamin D deficiency is not associated with thinning of RNFL or macular volume in MS eyes unaffected by ON. This finding suggests the role of vitamin D in modulating the severity of MS is not exerted through an influence on neuredegeneration. (C) 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).