OBJECTIVE:To assess the sensitivity of optic coherence tomography (OCT) and visual evoked potentials (VEPs) to visual pathway abnormalities in multiple sclerosis (MS).
METHODS:A total of 40 MS subjects, 28 with optic neuritis (ON) at least 3 months before (bilateral in 5), underwent assessment of visual acuity, Expanded Disability Status Scale (EDSS), OCT and VEPs, the latter quantified with a 0-4 conventional score.
RESULTS:OCT and VEPs were abnormal in 36% and 56% respectively in all eyes (p=0.11), 68% and 86% in eyes with previous ON (p=0.12), and in 19% versus 40% in eyes without ON history (p=0.007). Combining VEP and OCT increased sensitivity to 89% in ON and 44% in non-ON eyes. Considering all eyes, global retinal nerve fibre layer (RNFL) thickness and VEP score were significantly correlated between them (ρ=-0.63, p<0.001) and with EDSS (RNFL: ρ=0.40, p<0.001; VEP score: ρ=0.47, p<0.001). Disease duration correlated with VEP score (ρ=0.25, p=0.025) and RNFL thickness (ρ=-0.71, p<0.001).
CONCLUSIONS: In eyes without ON, VEPs were more frequently abnormal than OCT, while the two techniques showed similar sensitivity in eyes previously affected by ON. The correlation of VEPs and OCT measures with disability prompts further exploration of the two techniques as potential markers of disease burden.
OCT is like ultrasound of the eye using light rather than sound but it detects nerve loss in the eye as a result of nerve loss in the optic nerve. Visual evoke potentials measure changes occurring in the the pathway between the eye and the brain and can pick up loss of nerves and loss of myelin. When there was optic neuritis detected in the eyes both techniques could pick it up, but when optic neuritis was not detected VEP were more likely to show up differences which is hardly surprising as one would suspect that VEP is a more sensitive marker.