Hagan Richard P, Fisher Anthony C, Brown Malcolm C
Clinical Engineering Department, Duncan Building, Royal Liverpool University Hospital, Prescot Street, Liverpool, L9 8XP, UK.
Doc Ophthalmol. 2006 Jul;113(1):21-7. doi: 10.1007/s10633-006-9009-x. Epub 2006 Aug 30.
The mfERG, when first introduced by Erich Sutter used long sequences with short periods (approximately 15 ms) between steps (flashes). Since then a number of studies have introduced slower or modified sequences to emphasise Oscillatory Potentials (OPs), Optic Nerve Head Components (ONHC) or the s-wave. With this reduction in the rate of presentation many of the investigators have reduced the length of the sequence to allow a shorter recording period. This is also desirable for patient comfort and co-operation in diagnostic investigations. When reducing the length of the sequence there is a risk that it will be too short to ensure orthogonality of the first order component and all significant higher order components, particularly when a large number of areas (hexagons) are stimulated. This paper aims to verify that a short sequence (using the sequence used by the Roland Retiscan stimulating 19 hexagons) is capable of keeping responses of both first and higher orders separate for each stimulating area. The sequence was investigated by placing photodiodes connected to a Diagnosys Espion and then exported to Excel and MATLAB for analysis. It was determined that the sequences used were m-sequences length n = 9. The photodiode only responded to flashes of light so was unable to detect a correcting 0 at the end of sequence. The sequences driving each hexagon were then determined and found to be shifted 26 steps from each other. The correlation coefficients between all sequences was found to be -1/(2n -1). The sequences to decode the second order kernels were determined and the correlation coefficients between each of these sequences, and between these and the original sequences, were also -1/(2n -1). This work provides a mathematical validation of the use of short sequences for slow mfERG, and describes an empirical test method.
最初由埃里希·萨特引入的多焦视网膜电图（mfERG）使用的是步长（闪光）之间周期较短（约15毫秒）的长序列。从那时起，许多研究引入了更慢或经过修改的序列，以突出振荡电位（OPs）、视神经乳头成分（ONHC）或s波。随着呈现速率的降低，许多研究者缩短了序列长度，以缩短记录周期。这对于患者在诊断检查中的舒适度和配合度也是很有必要的。在缩短序列长度时，存在序列过短而无法确保一阶成分和所有重要高阶成分正交性的风险，尤其是在刺激大量区域（六边形）时。本文旨在验证短序列（使用罗兰视网膜扫描仪刺激19个六边形时使用的序列）能够使每个刺激区域的一阶和高阶反应保持分离。通过将连接到Diagnosys Espion的光电二极管放置好，然后导出到Excel和MATLAB进行分析，对该序列进行了研究。确定所使用的序列是长度n = 9的m序列。光电二极管仅对闪光有反应，因此无法检测序列末尾的校正0。然后确定驱动每个六边形的序列，发现它们彼此之间相差26步。发现所有序列之间的相关系数为-1/(2n - 1)。确定了解码二阶核的序列，并且这些序列之间以及它们与原始序列之间的相关系数也为-1/(2n - 1)。这项工作为慢mfERG使用短序列提供了数学验证，并描述了一种实证测试方法。
