Multifocal visual evoked potentials for quantifying optic nerve dysfunction in patients with optic disc drusen

PurposeTo explore the applicability of multifocal visual evoked potentials (mfVEPs) for research and clinical diagnosis in patients with optic disc drusen (ODD). This is the first assessment of mfVEP amplitude in patients with ODD. MethodsMfVEP amplitude and latency from 33 patients with ODD and 22 control subjects were examined. Mean amplitude, mean inner ring (IR) amplitude (0.87-5.67 degrees of visual field) and mean outer ring amplitude (5.68-24 degrees of visual field) were calculated using signal-to-noise ratio (SNR) and peak-to-peak analysis. Monocular latency was calculated using second peak analysis, while latency asymmetry was calculated using cross-correlation analysis. ResultsCompared to normals, significantly decreased mean overall amplitude (p<0.001), IR amplitude (p<0.001) and outer ring amplitude (p<0.001) were found in ODD patients when using SNR. An overall monocular latency delay of 7ms was seen in ODD patients (p=0.001). A significant correlation between amplitude and automated perimetric mean deviation as well as retinal nerve fibre layer thickness was found (respectively, p<0.001 and p=0.003). The overall highest correlation was found in this order: outer ring, full eye and IR. In the control group, SNR intersubject variability was 17.6% and second peak latency intersubject variability was 2.8%. ConclusionDecreased mfVEP amplitude in patients with ODD suggests a direct mechanical compression of the optic nerve axons. Our results suggest that mfVEP amplitude is applicable for the assessment of optic nerve dysfunction in patients with ODD.