Department of Clinical Sciences, Swedish University of Agricultural Sciences, PO Box 7054, SE-750 07, Uppsala, Sweden.
BMC Vet Res. 2020 Jul 29;16(1):261. doi: 10.1186/s12917-020-02463-8.
Visual evoked potentials (VEPs) are electrical potentials generated by neurons in the central nervous system in response to visual stimuli. A series of positive and negative wavelets in response to flash-stimuli (flash-VEP; FVEP) or reversing, iso-luminant patterns (pattern-VEP; PVEP) are recorded. Pathological conditions affecting the post-retinal pathways can alter overall waveform morphology, and also affect wavelet peak times and amplitudes. FVEPs have recently been described in horses, but more data on the variability within and between subjects is required, to adequately interpret results from clinical equine patients. Therefore, the purpose of this study was to describe the variability, repeatability and test-retest reliability of equine FVEPs in normal, adult horses.
Equine FVEPs were recorded from one randomly selected eye in 17 horses, from both eyes in eight of these horses, and also at two separate recording sessions in six horses. N1, P2, N2 and P4 wavelets were present in 100% of the recordings in all horses, while P1, N2a, P3 and P5 were only present in some recordings. Coefficients of variation (CVs) were low for P2, N2 and P4 peak times, but higher for all amplitudes. There were no statistically significant differences comparing peak times and amplitudes between eyes or between sessions. Coefficients of repeatability (CRs) are reported for P2, N2 and P4 peak times between eyes (P2; 5 ms, N2; 18 ms, P4; 18 ms) and also between sessions (P2; 5 ms, N2; 16 ms, P4; 39 ms). Intraclass correlation coefficients (ICCs), as an estimate of test-retest reliability, was assessed to be fair to excellent for most parameters.
This study provides important data on variability, repeatability and test-retest reliability of FVEPs in normal, adult horses. We conclude that P2, N2 and P4 peak times should be included in the evaluation of equine FVEPs. The large inherent variability of FVEP amplitudes is likely to make them less suitable and useful for establishing a diagnosis on their own in most clinical patients, but they may occasionally provide support to a clinical diagnosis.
视觉诱发电位（VEPs）是中枢神经系统神经元对视觉刺激的电反应。闪光刺激（FVEP）或反转、等亮度模式（PVEP）会产生一系列的正、负小波。影响视网膜后通路的病理状况会改变整个波形形态，也会影响小波峰的时间和幅度。FVEP 最近在马中被描述过，但需要更多关于个体内和个体间变异性的数据，以便充分解释临床马患者的结果。因此，本研究旨在描述正常成年马的 FVEP 的变异性、可重复性和测试-重测信度。
在 17 匹马中，随机选择一只眼记录了马的 FVEP，其中 8 匹马的双眼都记录了，6 匹马在两次单独的记录中都记录了。在所有马的记录中，都存在 N1、P2、N2 和 P4 小波，而 P1、N2a、P3 和 P5 仅在一些记录中存在。P2、N2 和 P4 峰时间的变异系数（CV）较低，但所有幅度的 CV 都较高。比较双眼和两次记录之间的峰时间和幅度，没有统计学上的显著差异。报告了 P2、N2 和 P4 峰时间的重复性系数（CR），双眼之间（P2；5ms，N2；18ms，P4；18ms）和两次记录之间（P2；5ms，N2；16ms，P4；39ms）。作为测试-重测可靠性的估计，内类相关系数（ICC）评估为大多数参数的中等至良好。
本研究提供了正常成年马 FVEP 变异性、可重复性和测试-重测信度的重要数据。我们得出结论，P2、N2 和 P4 峰时间应该包括在马的 FVEP 评估中。FVEP 幅度的固有大变异很可能使它们在大多数临床患者中不太适合和有用，无法单独做出诊断，但它们可能偶尔会为临床诊断提供支持。
