Corneal Confocal Microscopy: An Imaging Endpoint for Axonal Degeneration in Multiple Sclerosis

To evaluate whether corneal confocal microscopy (CCM) detects axonal degeneration and whether this is associated with retinal nerve fiber degeneration and clinical disability in patients with multiple sclerosis (MS).

Twenty-five patients with MS and 25 healthy control subjects underwent CCM, optical coherence tomography (OCT), and assessment of neurological disability using the expanded disability status scale (EDSS) and MS severity score (MSSS).

In patients with MS compared with controls, there was a significant reduction in corneal nerve fiber density (CNFD), branch density (CNBD), and length (CNFL). There was no significant difference in CCM parameters between patients with optic neuritis (MS-ON) and without (MS-NON), or between relapsing-remitting (RRMS) and secondary-progressive MS (SPMS). There was significant thinning of the retinal nerve fiber layer (RNFL) in the global, temporal, temporal superior, and temporal inferior quadrants, with no difference between MS-ON and MS-NON. Patients with SPMS compared with RRMS had a significantly lower global, temporal superior, temporal inferior, nasal, and nasal superior RNFL. The EDSS and MSSS correlated significantly with CNBD, nasal, nasal superior, and nasal inferior RNFL and with CNBD and nasal inferior RNFL, respectively.

CCM and OCT detect significant corneal and retinal nerve degeneration which relates to the severity of neurological deficits in patients with mild MS.