Tony Kriss Visual Electrophysiology Unit, Clinical and Academic, Department of Ophthalmology, Great Ormond Street Hospital for Children, London, WC1N 3JH, UK.
Manchester Metropolitan University, Manchester, UK.
Doc Ophthalmol. 2021 Apr;142(2):165-176. doi: 10.1007/s10633-020-09785-w. Epub 2020 Jul 20.
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.
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°.
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.
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.
视觉诱发电位（VEPs）评估从视网膜到初级视觉皮层的视觉通路的功能。有大量证据表明，单眼模式反转和闪光 VEP 可以区分因视交叉和视交叉后传入通路损伤引起的功能障碍。关于使用模式起始/结束 VEP 来识别视交叉后功能障碍的证据较少。
我们介绍了 9 例具有不同程度视觉通路缺陷的患者，这些患者的致密偏盲性视野缺损。这些患者的视交叉后功能障碍，记录了从枕部电极排列的模式起始/结束 VEP，参考中额电极，检查在背景平均亮度下出现 230 毫秒，消失 300 毫秒，刺激场为 30°。
我们发现，模式起始 VEP 成分偏向于覆盖功能半球的枕部电极，而模式结束 VEP 成分则表现出反转 VEP 中描述的反常侧化现象，在对侧枕部最大。
我们的发现表明，如何延长记录时间窗口以包括结束 VEP，有助于识别偏盲性视野缺损。我们主张在评估偏盲患者时使用模式起始/结束 VEP，对视交叉后功能障碍患者尤其有价值，这些患者无法进行更具挑战性的半视野电生理学、影像学或心理物理学测试。
