Pham Brandon H, Goldberg Jeffrey L, Marmor Michael F
Stanford University School of Medicine, 291 Campus Drive, Li Ka Shing Building, Stanford, CA, 94305, USA.
Department of Ophthalmology, Byers Eye Institute at Stanford, 2452 Watson Court, Palo Alto, CA, 94303, USA.
Doc Ophthalmol. 2020 Dec;141(3):253-257. doi: 10.1007/s10633-020-09769-w. Epub 2020 Jun 7.
The photopic negative response (PhNR) correlates with ganglion cell function and has previously been examined as an indicator of glaucomatous optic nerve damage. However, it is a prolonged response that is measured against baseline, and its clinical utility has been limited by extensive variability, poor repeatability, and baseline instability. We have observed a distinct brief negative wave ("N-wave") commonly present within the slow PhNR trough, which may provide practical and analytic advantages as a clinical measure.
We reviewed data from an interventional trial of 59 glaucoma patients who had 4 exams over an 8-month period. The PhNR was recorded with standard ISCEV stimuli (1 Hz and in some cases 4 Hz stimulation), and N-waves were measured manually, relative to return to baseline.
N-waves, when present, could be measured easily despite shifting baselines and a degree of background noise. The PhNR median amplitude centered around 18 μV, while the N-wave median centered around 7 μV, with a distribution of responses skewed toward low or zero amplitudes.
The N-wave appears to be a component of the longer PhNR, though its exact origin and significance remain unclear. As a rapid waveform that is independent of baseline, the N-wave is in many ways easier to measure accurately than the slower PhNR, which is highly dependent on baseline stability. The N-wave may prove useful clinically if further studies can optimize its stimulation, show its behavior in normal individuals and find correlation with markers of optic nerve disease.
明视负反应（PhNR）与神经节细胞功能相关，此前已被作为青光眼性视神经损伤的一项指标进行研究。然而，它是一种相对于基线测量的延长反应，其临床应用受到广泛变异性、较差的可重复性和基线不稳定性的限制。我们观察到在缓慢的PhNR波谷内通常存在一个明显的短暂负波（“N波”），作为一种临床测量指标，它可能具有实际和分析上的优势。
我们回顾了一项针对59例青光眼患者的干预性试验的数据，这些患者在8个月内接受了4次检查。使用标准的国际临床视觉电生理学会（ISCEV）刺激（1Hz，在某些情况下为4Hz刺激）记录PhNR，并相对于基线恢复情况手动测量N波。
尽管基线发生变化且存在一定程度的背景噪声，但当N波出现时仍可轻松测量。PhNR的中位振幅集中在18μV左右，而N波的中位振幅集中在7μV左右，反应分布向低振幅或零振幅倾斜。
N波似乎是较长的PhNR的一个组成部分，尽管其确切起源和意义尚不清楚。作为一种独立于基线的快速波形，N波在许多方面比高度依赖基线稳定性的较慢的PhNR更容易准确测量。如果进一步的研究能够优化其刺激方式，展示其在正常个体中的表现并找到与视神经疾病标志物的相关性，N波可能在临床上证明是有用的。
