Rubin Glen R, Kraft Timothy W
Department of Vision Sciences, University of Alabama at Birmingham, 924 18th Street South, Worrell Building, Birmingham, AL 35294-4390, USA.
Doc Ophthalmol. 2007 Nov;115(3):165-72. doi: 10.1007/s10633-007-9066-9. Epub 2007 Aug 3.
Critical flicker frequency (CFF) is the lowest frequency for which a flickering light is indistinguishable from a non-flickering light of the same mean luminance. CFF is related to light intensity, with cone photoreceptors capable of achieving higher CFF than rods. A contemporaneous measure of rod and cone function can facilitate characterization of a retinal degeneration. We used sinusoidal flicker ERG to obtain CFF values, over a wide range of light intensities, in RCS dystrophic (RCS-p(+)) and wild type rats. Recordings were made at PN23, PN44, and PN64. The CFF curve in control animals increased in proportion to the log of stimulus intensity, with a gentle slope over the lowest 4 log-unit intensity range. The slope of the CFF curve dramatically increased for higher intensities, indicating a rod-cone break. In the RCS rats the rod driven CFF was significantly lower in amplitude compared to normal rats at the earliest age tested (PN23). By PN64 the rod driven CFF was immeasurable in the RCS rats. The amplitude of the cone driven CFF approached normal values at PN23, but was greatly reduced by PN44. By PN64 the entire CFF function was greatly depressed and there was no longer a discernable rod-cone break. These CFF/ERG data show that RCS rats exhibit significant early degeneration of the rods, followed soon after by degeneration of the cones. Using this approach, rod and cone function can be independently accessed using flicker ERG by testing at a few select intensities.
临界闪烁频率（CFF）是指闪烁光与具有相同平均亮度的非闪烁光无法区分的最低频率。CFF与光强度有关，锥状光感受器能够实现比杆状光感受器更高的CFF。同时测量杆状和锥状光感受器的功能有助于对视网膜变性进行特征描述。我们使用正弦闪烁视网膜电图（ERG）在广泛的光强度范围内获取了RCS营养不良大鼠（RCS-p(+)）和野生型大鼠的CFF值。记录在出生后第23天（PN23）、第44天（PN44）和第64天（PN64）进行。对照动物的CFF曲线与刺激强度的对数成比例增加，在最低的4个对数单位强度范围内斜率平缓。对于更高的强度，CFF曲线的斜率显著增加，表明存在杆状-锥状光感受器转换点。在最早测试的年龄（PN23），RCS大鼠中杆状光感受器驱动的CFF幅度与正常大鼠相比显著降低。到PN64时，RCS大鼠中杆状光感受器驱动的CFF无法测量。锥状光感受器驱动的CFF幅度在PN23时接近正常值，但在PN44时大幅降低。到PN64时，整个CFF功能大幅下降，不再有可辨别的杆状-锥状光感受器转换点。这些CFF/ERG数据表明，RCS大鼠的杆状光感受器早期出现明显退化，随后不久锥状光感受器也发生退化。使用这种方法，通过在几个选定的强度下进行测试，可以使用闪烁ERG独立评估杆状和锥状光感受器的功能。
