Hood D C, Birch D G
Department of Psychology, Columbia University, New York, NY 10027.
Invest Ophthalmol Vis Sci. 1994 Jun;35(7):2948-61.
Relationships between the Lamb and Pugh model of transduction in single rod photoreceptors and the parameters derived from human rod a-waves are examined to evaluate transduction abnormalities in retinitis pigmentosa (RP) and cone-rod dystrophy (CRD).
ERGs were obtained from 15 patients, 11 with RP and 4 with CRD, and from 15 normal subjects. Rod-only responses were derived from responses to blue (W47B) flashes over a wide range of flash energies by computer-subtracting estimates of the cone contribution. A model of the rod's response was fitted to the a-waves of the rod-only responses as well as to the responses to the blue flashes by estimating three parameters-sensitivity (S), delay (td), and maximum response (RmP3). To assess the limits of the cone contributions to the parameters of the model, ERGs were obtained from two of the patients, two normal subjects, and three additional patients with nondetectable rod responses using white flashes.
All patients had significantly decreased values of RmP3, and eight had significantly decreased values of S compared to the control subjects. The values of the parameters estimated from the responses to the blue flashes were reasonably similar to those for the rod-only responses except in patients with nondetectable rod signals. For the white flashes, the estimate of S was considerably larger and the fit of the model noticeably poorer.
The authors reached two conclusions. First, some forms of RP and CRD alter the activation stages of transduction. Transduction appears normal in other patients, despite extensive receptor damage as indicated by markedly reduced RmP3 values. Second, the cone contribution to a blue flash only affects the estimate of the key parameters in patients in whom the rod component is minimal. The cone contribution to a white flash contaminates the fit and the estimate of the parameters in all patients and normal subjects.
研究单根视杆光感受器中兰姆（Lamb）和普格（Pugh）转导模型与源自人类视杆a波的参数之间的关系，以评估视网膜色素变性（RP）和锥杆营养不良（CRD）中的转导异常。
从15名患者（11名RP患者和4名CRD患者）以及15名正常受试者中获取视网膜电图（ERG）。通过计算机减去对视锥贡献的估计值，从对广泛闪光能量的蓝色（W47B）闪光反应中得出仅视杆反应。通过估计三个参数——敏感度（S）、延迟（td）和最大反应（RmP3），将视杆反应模型拟合到仅视杆反应的a波以及对蓝色闪光的反应上。为了评估视锥对模型参数贡献的限度，使用白色闪光从两名患者、两名正常受试者以及另外三名视杆反应不可检测的患者中获取ERG。
与对照组相比，所有患者的RmP3值均显著降低，8名患者的S值显著降低。从对蓝色闪光的反应中估计的参数值与仅视杆反应的参数值相当相似，除了视杆信号不可检测的患者。对于白色闪光，S的估计值明显更大，模型的拟合明显更差。
作者得出两个结论。第一，某些形式的RP和CRD会改变转导的激活阶段。尽管RmP3值显著降低表明存在广泛的感受器损伤，但在其他患者中转导似乎正常。第二，视锥对蓝色闪光的贡献仅影响视杆成分最小的患者中关键参数的估计。视锥对白色闪光的贡献会干扰所有患者和正常受试者中参数的拟合和估计。
