Documenta ophthalmologica. Advances in ophthalmology · 2020
Pattern-onset and OFFset visual evoked potentials in the diagnosis of hemianopic field defects.
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Marmoy Oliver R, Handley Sian E, Thompson Dorothy A
Аннотация
BACKGROUND: Visual evoked potentials (VEPs) assess the function of the visual pathway from the retina to the primary visual cortex. There is much evidence that monocular pattern-reversal and flash VEPs can distinguish dysfunction due to chiasmal and post-chiasmal afferent pathway lesions. There is less evidence about the use of pattern-onset/OFFset VEPs to identify post-chiasmic dysfunction.
METHODS: We present nine patients with a range of visual pathway defects that caused dense hemianopic field defects. These patients had pattern onset-OFFset VEPs recorded from an array of occipital electrodes referred to a mid-frontal electrode to checks that appeared for 230 ms and disappeared for 300 ms into a background of mean luminance, in a stimulus field of 30°.
RESULTS: We found pattern-onset VEP components lateralise to occipital electrodes overlaying the functional hemisphere, whereas pattern-OFFset VEP components demonstrate the paradoxical lateralisation phenomenon, described in reversal VEPs, and are maximal over the contralateral occiput.
CONCLUSION: Our findings show how extending the recording time window to include an OFFset VEP facilitates identification of hemianopic visual field defects. We advocate the pattern-onset/OFFset VEP in the assessment of patients with hemianopia, having particular value for patients who are otherwise unable to perform more demanding half-field electrophysiology, imaging or psychophysical testing.
METHODS: We present nine patients with a range of visual pathway defects that caused dense hemianopic field defects. These patients had pattern onset-OFFset VEPs recorded from an array of occipital electrodes referred to a mid-frontal electrode to checks that appeared for 230 ms and disappeared for 300 ms into a background of mean luminance, in a stimulus field of 30°.
RESULTS: We found pattern-onset VEP components lateralise to occipital electrodes overlaying the functional hemisphere, whereas pattern-OFFset VEP components demonstrate the paradoxical lateralisation phenomenon, described in reversal VEPs, and are maximal over the contralateral occiput.
CONCLUSION: Our findings show how extending the recording time window to include an OFFset VEP facilitates identification of hemianopic visual field defects. We advocate the pattern-onset/OFFset VEP in the assessment of patients with hemianopia, having particular value for patients who are otherwise unable to perform more demanding half-field electrophysiology, imaging or psychophysical testing.