Study of the mechanism of visual function in incomplete type of congenital stationary night blindness

我们研究了完全型和不完全型先天性静止性夜盲症（CSNB）的视功能机制，结果如下。采用从接近绝对阈值到明亮的全视野刺激，记录完全性、不完全性CSNB患者和正常人的ERG强度序列。完全性CSNB患者的棒状b波和STR均不可记录。在不完全CSNB中，STR明显可记录，尽管绝对阈值略有升高。b波刺激阈值未升高，阈值附近的b波振幅正常。STR波峰值时间延迟约80毫秒，而b波峰值时间正常。以上结果提示，完全型夜盲症的发病位点可能位于杆状双极细胞，而不完全型夜盲症的发病位点可能位于杆状双极细胞的近端。视杆-视锥相互作用适应黑暗的视杆对视锥反应有抑制作用。应用这一现象分析CSNB的病理机制。我们的研究结果表明，在完全和不完全CSNB中，SRCI是正常的，但在某些情况下，由于局限性视网膜功能障碍，SRCI缺失。

We studied the mechanism of visual function in complete and incomplete type of congenital stationary night blindness (CSNB) with the following results.1.Locus of night blindnessUsing full-field stimuli with light intensities ranging from near absolute threshold to bright, ERG intensity series from patients with complete and incomplete CSNB and from normal subjects were recorded. Neither the rod b-wave nor the STR was recordable from patients with complete CSNB.In the incomplete CSNB,the STR was clearly recordable, although the absolute threshold was elevated slightly. The b-wave stimulus threshold was not elevated, and the b-wave amplitude near threshold was normal. The peak time of the STR was delayd by approximately 80 msec, whereas that of b-wave was normal.Above results suggest that the locus of the night blindness of the complete type may lie in the rod bipolar cell, while that of incomplete type may lie proximal to the rod bipolar cell.2.Rod-cone interactionDark-adapted rods have a suppressive effect on cone response (SRCI). This phenomenon was applied to analyze the pathological mechanism of CSNB.Our results indicated that SRCI is normal in both complete and incomplete CSNB,but in some cases, SRCI is absent because of localized retinal dysfunction.