Rahman Anmar M A, Sanderson Gordon F
School of Optometry and Vision Science, University of New South Wales, New South Wales, Australia.
Optom Vis Sci. 2008 Jul;85(7):547-58. doi: 10.1097/OPX.0b013e31817dba51.
Frequency doubling technology (FDT) is a recent psychophysical test for glaucoma. It measures the contrast threshold to low spatial frequency, high temporal frequency sinusoidal luminance profile bars. We wanted to confirm, with stricter controls, Vaegan and Hollow's report that contrast thresholds of steady state visual evoked potentials (ssVEPs) to a stimulus resembling the central field of the FDT test was more sensitive to glaucoma than the subjective threshold to the same stimulus and to start to optimize the technique.
A double masked trial using 57 eyes of 42 subjects. Both thresholds were estimated by modified binary search. In psychophysical testing, subjects were given a two alternative forced choice task. In ssVEP testing a significant signal in any one of eight channels was deemed to be a detection. In some subjects electrode positions were compared, both eyes were tested, tests were repeated to estimate reliability, stimulus frequencies were varied or full contrast functions were obtained.
Thresholds and percent abnormal increased as a function of glaucoma severity for ssVEPs but not for psychophysics. Both threshold measures were reliable. Interocular correlations were low. SsVEP amplitude against contrast functions had similar thresholds to those found by modified binary search. The data was too irregular for individual thresholds to be estimated from a fitted exponential. Amplitudes were greatest at 7 to 10 Hz, < or =6 cm above inion and least laterally. Noise was similar across electrodes.
SsVEP contrast thresholds to a stimulus like the central field of the FDT test detected glaucoma better than corresponding psychophysical thresholds at 18.29 Hz, when formal controls were used, as they had in a less controlled previous study at 7.14 Hz.
倍频技术（FDT）是一种用于青光眼的最新心理物理学测试方法。它测量对低空间频率、高时间频率正弦亮度轮廓条的对比度阈值。我们希望通过更严格的对照，证实Vaegan和Hollow的报告，即对类似于FDT测试中心视野的刺激的稳态视觉诱发电位（ssVEP）的对比度阈值比相同刺激的主观阈值对青光眼更敏感，并开始优化该技术。
对42名受试者的57只眼睛进行双盲试验。两种阈值均通过改良二分法搜索进行估计。在心理物理学测试中，受试者被给予二选一的强制选择任务。在ssVEP测试中，八个通道中任何一个通道的显著信号都被视为检测到。在一些受试者中，比较了电极位置，对双眼进行了测试，重复测试以估计可靠性，改变了刺激频率或获得了完整的对比度函数。
ssVEP的阈值和异常百分比随青光眼严重程度增加，而心理物理学测试则不然。两种阈值测量方法都可靠。两眼之间的相关性较低。ssVEP振幅与对比度函数的阈值与改良二分法搜索得到的阈值相似。数据过于不规则，无法从拟合指数中估计个体阈值。振幅在7至10Hz时最大，在枕外隆凸上方≤6cm处，外侧最小。各电极的噪声相似。
当使用正式对照时，对类似于FDT测试中心视野的刺激的ssVEP对比度阈值在18.29Hz时比相应的心理物理学阈值能更好地检测青光眼，正如他们在之前控制较差的7.14Hz研究中所做的那样。
