Color vision impairment in multiple sclerosis and neuromyelitis optica spectrum disorder

Introduction
To evaluate the color vision impairment in multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD) and its relation to retinal neurovascular parameters measured by spectral-domain optical coherence tomography (SDOCT) and OCT angiography (OCTA).

Material and methods
A total of 40 relapsing-remitting MS patients, 13 aquaporin-4 antibody-positive NMOSD patients, and 20 healthy controls were included. MS and NMOSD were divided into groups: eyes with a history of optic neuritis (MS+ON, NMOSD+ON) and eyes without previous ON (MS-ON, NMOSD-ON). Color vision was assessed with the FarnsworthMunsell 100 hue test and results were presented as the square root of total error score (√TES) and total partial error score (√TPES) for the blue-yellow (B-Y) and red-green (R-G) axes. Ganglion cell complex (GCC) and retinal nerve fiber layer (RNFL) thickness was obtained with SD-OCT and vessel density of superficial, deep, and radial peripapillary capillary plexuses (SCP, DCP, RPC) was obtained with OCTA.

Results
√TES, B-Y, and R-G √TPES were significantly higher in MS+ON, MS-ON, NMOSD+ON, and NMOSD-ON than in the control group. Color vision was comparable between MS+ON and MS-ON, whereas in NMOSD+ON, it was significantly more impaired than in NMOSD-ON and MS+ON. Within the groups, the severity of dyschromatopsia did not differ between the B-Y and R-G axes. √TES correlated with GCC thickness only in NMOSD-ON eyes, while in MS+ON, an association between √TES and vessel density of SCP and RPC was observed. Color vision did not correlate with RNFL thickness and vessel density of DCP in any group.

Conclusions
Color vision defects were found in MS and NMOSD eyes, regardless of the history of ON. No specific predilection towards the blue-yellow or red-green axis was detected.