视网膜电图和多焦视网膜电图视杆细胞ON和OFF反应记录研究

目的:研究全视野视网膜电图(electroretinogram,ERG)和多焦视网膜电图(multifocal eletroretinogram,mf-ERG)视杆细胞ON和OFF反应记录条件并分析其波形特征。方法:2例正常人放瞳、暗适应30 min后,分别采用矩形刺激(rectangle stimulus)、锯齿状的 rapid on和rapid off刺激模式记录反应波形,并改变刺激强度和频率观察波形变化。采用模拟矩形刺激、锯齿状的rapid on和rapid off刺激模式记录mf-ERG波形。结果:ERG采用矩形和rapid-on刺激模式可记录到大的正向波,随刺激频率增加,振幅减小, 潜伏时变化不明显。采用rapid-off刺激模式记录到小的负向波,潜伏时80 ms左右,在负向波下降支近波谷处可见小的正向波。随刺激频率增加,负向波潜伏时延长,而小正向波振幅逐渐减小。当刺激频率大于3 Hz时,上述反应均出现类似振荡电位波形。mf-ERG采用模拟矩形和模拟rapid-on刺激模式可记录到大的正向波,其波形特征与ERG矩形刺激模式的波形类似;采用模拟rapid-off刺激模式仍可记录大的正向波,但其后出现较大陡峭的负向波。结论:采用锯齿状的rapid-on和rapid-off刺激模式可以记录到视杆细胞ON和OFF反应,视杆细胞OFF反应的负向波下降支近波峰处存在小的正向波,采用模拟的rapid-on刺激模式记录到mf-ERG视杆细胞ON反应。建议记录ERG视杆细胞ON和OFF反应采用0．5-1Hz 刺激频率和低强度刺激光。将来可利用这些刺激模式研究视网膜疾病,具有一定的临床价值。

Recording Rod ON and OFF Responses in ERG and Multifocal ERG

Purpose: To investigate feasibility and recording conditions of recording rod on and off responses in electroretinograms (ERG) and multifocal electroretinograms (mf-ERG), and observe character and influence factors of these responses. Methods : ERG responses were recorded using the rectangle stimulus, sawtooth rapid- on and rapid-off stimulus in normal subjects after dark adaptation. Flash frequency and flash intensities varied to obtain appropriate recording conditions for clinical use. Mf-ERG responses were recorded in using simulated rectangle stimulus, saw tooth rapid-on and rapid-off stimulus. Results: A large positive wave was found in ERG of rectangle stimulus and rapid-on stimulus. Increasing flash frequency decreased response amplitudes, however, the latency time changed little. A small negative wave with 80 ms latency time was found in ERG of rapid-off stimulus, and a very small positive wave with 75 ms latency time was found in the downhill of the negative wave. Increasing flash frequency increased latency time of the negative wave, but decreased the amplitude of the small positive wave. Oscillatory wave-like waves were found in the responses when flash frequency increased to 3 Hz. A large negative wave following a positive wave was found in mf-ERG of simulated rapid-off stimulus, which was difference from the wave of simulated rectangle stimulus and rapid-on stimulus. Conclusions: Rod on and off responses of ERG can be recorded with sawtooth rapid-on and rapid-off stimulus. There is a small positive wave in downhill of negative wave in rod off response. Rod on response of mf-ERG can be recorded with simulated rapid-on stimulus. The flash frequency of 0.5-1Hz and small flash intensity were suggested to appropriate conditions for recording rod on and off responses in ERG. The simulated rapid-on, sawtooth rapid-on and rapid-off stimulus can be used to investigate retinal disease.