Axonal loss in the retinal nerve fiber layer in patients with multiple sclerosis

To quantify axonal loss in the retinal nerve fiber layer (RNFL) in patients with multiple sclerosis (MS), with and without a history of optic neuritis, by means of ocular imaging technologies.

This cross-sectional study enrolled 50 patients with MS and 25 age- and sex-matched healthy controls. All patients underwent neurologic assessment and a complete ophthalmic examination that included visual acuity, visual field examination, optical coherence tomography (OCT), scanning laser polarimetry (GDx) and visual evoked potentials (VEPs). Visual parameters and RNFL measurements were evaluated in MS eyes with a prior optic neuritis episode (MS-ON), with no prior episode (MS-NON) and control subjects.

There were significant differences (p < 0.05, analysis of variance) between MS-ON (n = 25 eyes) and healthy eyes (n = 25 eyes) for all RNFL parameters measured by OCT and GDx. Significant differences between MS-NON (n = 75 eyes) and healthy eyes were also found for most of these parameters. RNFL thickness in the temporal quadrant was the parameter with the greatest differences between groups (71.79 microm in healthy eyes, 60.29 microm in MS-NON and 53.92 microm in MS-ON, p < 0.0005). Although there was a highly significant but moderate correlation between RNFL thickness and duration of the disease, no correlation was observed between RNFL thickness and neurologic impairment (Expanded Disability Status Scale).

Axonal loss was detected not only in MS eyes with a previous acute optic neuritis, but also in MS eyes with no known optic neuritis episode. Structural abnormalities correlate with functional assessments of the optic nerve.