Chromatic visual evoked potentials in young patients with demyelinating disease

Abstract

The purpose of this study was to evaluate color vision in young patients with demyelinating disease both clinically and electrophysiologically. Thirty young patients (8-28 years, mean age 19 years) with demyelinating disease with or without a history of optic neuritis (ON) were investigated. Color vision was evaluated clinically with the Ishihara test and the Farnsworth-Munsell 100 hue (FM 100 hue) test and electrophysiologically with chromatic visual evoked potentials (cVEPs). Color deficiency axis and error score (ES) obtained with the FM 100 hue test were analyzed. cVEPs to isoluminant red-green (R-G) and blue-yellow (B-Y) stimuli were recorded. The stimulus was a 7 deg circle composed of horizontal sinusoidal gratings with a spatial frequency of 2 cycles/deg and 90% chromatic contrast. Onset-offset mode of stimulation (ON:OFF=300∶700 ms) was used. Since the majority of the patients were adults (>18 years), the negative wave (N wave) of the cVEP respones is the prominent part and therefore was analyzed. Sixty eyes were studied-22 with at least one episode of ON (ON group) and 38 without any clinically evident episode of ON (nON group). The average ES in the ON group was 179.18±171.8, whereas in the nON group it was 87.60±65.34. The average N-wave latency in the ON group was 144±44 ms for the R-G stimulus and 146±56 ms for the B-Y stimulus, whereas in the nON group, it was 117±13 ms for the R-G stimulus and 121±22 ms for the B-Y one. The average N-wave amplitude in the ON group was 9.3±7.1 μV for the R-G stimulus and 5.1±3.9 μV for the B-Y one, whereas in the nON group, it was 10.8±8.3 μV for the R-G stimulus and 6.4±4.3 μV for the B-Y one. A significant difference between the ON and the nON group was found: in the ON group, ES was higher (p=0.01) and N-wave latency was longer (p=0.01) compared with those in the nON group. The study showed that color vision is expectedly more affected in the ON group, but also often in the nON group, which may indicate increased parvocellular visual pathway vulnerability in demyelinating diseases.

Analysis of Color-Specific Visual Processing Speed Differences in Division 1 College Football Players

“…Color vision loss and demyelinating disorders such as optic neuritis have been linked with retinal axonal loss visible in OCT imaging 9,14 and to increased error scores and N-wave latencies in VEP waveforms. [15][16][17][18][19] The players' baseline OCT scans, however, revealed that retina, optic nerve head, and ganglion cell complex anatomy are within normal, healthy limits (data not shown and Bixenmann et al 9 ). This suggests that the players' red/green differences are due to optic nerve or retinal dysfunction.…”

“…15 The neural generators of N75 and P100 are in the primary visual cortex, and the two components are physiologically distinct. 17,18,20,21 Furthermore, L/M cone signal processing already present in the retina and LGN is also observed at the visual cortex and a lack of either photoreceptor types led to a dominance of the ON pathways of the remaining photoreceptor type. 7,15 This inverse relationship may explain why our players have diminished perception of and speed with red, which is significantly different from green.…”