Retinal nerve fiber layer thickness associates with cognitive impairment and physical disability in multiple sclerosis

Background: Reductions of the peripapillary retinal nerve fiber layer (pRNFL) thickness has been indicated even in early-stages of multiple sclerosis (MS). The aim was to investigate the association between pRNFL thickness, measured with optical coherence tomography (OCT), and physical disability and cognitive impairment in MS. Methods: 465 MS patients and 168 healthy controls (HCs) were included. MS subjects were divided into subgroups according to disease subtype. All subjects underwent OCT examination of all pRNFL quadrants using Canon OCT-HS100. Associations were tested using linear mixed effect models. Physical disability was assessed with the Expanded Disability Status Scale (EDSS) and cognitive function with the Symbol Digit Modalities Test (SDMT). Results: The average pRNFL, inferior pRNFL and temporal pRNFL thicknesses were significantly correlated to both EDSS (-1.0 mu m, p < 0.01; -1.2 mu m, p < 0.05; -1.2 mu m, p < 0.01) and SDMT (0.1 mu m, p < 0.05; 0.2 mu m, p < 0.05; 0.2 mu m, p < 0.01). A significant thickness loss compared with HCs was seen in the average pRNFL and in all quadrants except for the superior quadrant of primary progressive MS. The largest reduction compared with HCs was seen in the temporal pRNFL of PPMS eyes (-15.8 mu m; p < 0.001). Conclusion: The reduction of average pRNFL, inferior pRNFL and temporal pRNFL thickness is associated with physical and cognitive disability in MS. We suggest the use of temporal pRNFL as a more sensitive outcome as it showed the strongest association to both EDSS and SDMT.