Falsini B, Iarossi G, Fadda A, Porrello G, Valentini P, Piccardi M, Scullica L
Department of Ophthalmology, Catholic University, Rome, Italy.
Clin Neurophysiol. 1999 Sep;110(9):1554-62. doi: 10.1016/s1388-2457(99)00106-6.
The flicker electroretinogram (FERG) consists mainly of a linear (fundamental, 1F) and a non linear (second harmonic, 2F) component. Previous results indicate that 2F originates more proximally in the retina than 1F, and that retinitis pigmentosa (RP) may affect 2F to a greater extent than 1F. The aim of this study was to evaluate FERG 1F and 2F abnormalities in RP as a function of the stimulus temporal frequency (TF).
Twelve patients with typical RP and 10 age-matched controls were examined. FERGs were recorded in response to uniform fields (18 degrees) presented in the macula on a light-adapting background. Stimuli were flickered sinusoidally at different, closely spaced TFs between 3.7 and 52 Hz. Amplitudes and phases of the Fourier analysed 1F and 2F components were measured. Components' apparent latencies were estimated from the rate at which phase lagged with TF.
When compared to controls, mean 1F amplitudes of patients were reduced at both low (3.7-12.6 Hz) and high (14-52 Hz) TFs, with greatest losses (0.5 log units) around the peaks (3.7 and 41 Hz) of the normal TF function. Mean 2F amplitudes were reduced mainly at low TFs, with greatest losses (0.5 log units) at 5-8 Hz. On average, the shape of the 2F, but not 1F amplitude versus TF function, differed between patients and controls, showing a selective attenuation at low TFs. Mean 1F apparent latencies were delayed at both low and high TFs, with greater delays at low (85 ms) than at high (33 ms) TFs. Mean 2F apparent latencies were delayed only at low TFs (58 ms).
In RP, 1F and 2F phase delays as well as 2F amplitude losses are dependent on TF, suggesting that FERG generators' subpopulations in both distal and proximal retina are differentially affected. Analysis of the FERG TF response is potentially useful to characterize cone system dysfunction in different genetic subtypes of RP.
闪烁视网膜电图（FERG）主要由一个线性成分（基波，1F）和一个非线性成分（二次谐波，2F）组成。先前的研究结果表明，2F在视网膜中的起源比1F更靠近近端，并且视网膜色素变性（RP）对2F的影响可能比对1F的影响更大。本研究的目的是评估RP患者中FERG的1F和2F异常与刺激时间频率（TF）的关系。
对12例典型RP患者和10例年龄匹配的对照者进行检查。在光适应背景下，记录黄斑区呈现的均匀视野（18度）所诱发的FERG。刺激以3.7至52Hz之间不同的、间隔紧密的TF进行正弦闪烁。测量傅里叶分析后的1F和2F成分的振幅和相位。根据相位随TF的滞后速率估计成分的表观潜伏期。
与对照组相比，患者的平均1F振幅在低TF（3.7 - 12.6Hz）和高TF（14 - 52Hz）时均降低，在正常TF函数的峰值（3.7和41Hz）附近损失最大（0.5对数单位）。平均2F振幅主要在低TF时降低，在5 - 8Hz时损失最大（0.5对数单位）。平均而言，患者和对照组之间2F的形状（而非1F振幅与TF函数的关系）不同，在低TF时表现出选择性衰减。平均1F表观潜伏期在低TF和高TF时均延迟，低TF时（85ms）的延迟大于高TF时（33ms）。平均2F表观潜伏期仅在低TF时延迟（58ms）。
在RP中，1F和2F的相位延迟以及2F的振幅损失取决于TF，这表明视网膜远端和近端的FERG发生器亚群受到不同程度的影响。FERG TF反应分析可能有助于表征不同遗传亚型RP中的视锥系统功能障碍。
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