Do eyes with and without optic neuritis in multiple sclerosis age equally?

Purpose: Anterior visual pathway reflects axonal loss caused by both optic neuritis (ON) and neurodegeneration in multiple sclerosis (MS). Although the axonal injury post-ON is thought to be complete by 6 months of onset, most studies using optical coherence tomography (OCT) to evaluate retinal changes as a marker of neurodegeneration exclude eyes with a history of ON or consider them separately. The objective of this study was to assess whether the eyes post-ON (>6 months) show in later years different rate of chronic retinal changes than the fellow eyes not affected by ON. Patients and methods: Fifty-six patients with MS with a history of ON in one eye (ON eyes ) and no ON in the fellow (FL) eye, who were followed by OCT for >2 years, were selected from a cohort of patients with MS. Paired eye analysis was performed. Results: Mean interval post-ON at baseline was 5.65 (SD 5.05) years. Mean length of follow-up by OCT was 4.57 years. There was no statistical difference in absolute or relative thinning of retinal nerve fiber layer in peripapillary area between the ON and FL eyes. Conclusion: This study has shown that we do not need to exclude eyes with a history of ON from longitudinal studies of neurodegeneration in MS, provided that we use data outside of the frame of acute changes post-ON. Long-term changes of peripapillary retinal nerve fiber layer in ON and FL eyes are equal.