Optical coherence tomography in multiple sclerosis: thickness of the retinal nerve fiber layer as a potential measure of axonal loss and brain atrophy.

BACKGROUND: Axonal distribution within the retinal nerve fiber layer (RNFL) measured by optical coherence tomography (OCT) correlates with axonal viability and integrity. OBJECTIVE: To investigate correlations between RNFL and MRI measures of axonal loss in MS patients. METHODS: Fifty one remitting-relapsing MS patients, 20 with a history of optic neuritis (MS-ON), 31 without optic neuritis (MS N-ON), and 12 healthy control subjects (HC) were included in the study. RNFL was measured by OCT and brain atrophy was assessed by MRI. RESULTS: The average RNFL in the affected eye (AE) in the MS-ON group was significantly lower than the RNFL in the MS N-ON (p = 0.01) and in HC (p = 0.01). The average RNFL in the unaffected eye (UE) and RNFL in MS N-ON were also lower than HC, but this value did not achieve significance. In MS N-ON a lower average RNFL was associated with an increased T1 lesion volume (p = 0.03) and T2-lesion volume (p = 0.001). The RNFL in MS N-ON was also associated with a reduction of BPF and %gm fraction (p = 0.01, p = 0.02 respectively). In MS-ON there was a much weaker, non-significant correlation between RNFL thickness and T1, T2 volume, BPF, %gm and %wm fractions that might have resulted from a pronounced post-inflammatory local optic nerve atrophy in AE. CONCLUSION: The RNFL measured by OCT may be useful as a surrogate marker for assessment of brain atrophy in MS.