Falkenberg Helle K, Bex Peter J
Department of Optometry and Vision Science, Buskerud University College, Kongsberg, Norway.
Invest Ophthalmol Vis Sci. 2007 Jun;48(6):2913-21. doi: 10.1167/iovs.06-0752.
Primary open angle glaucoma (POAG) is a leading cause of irreversible adult blindness and is characterized by progressive optic neuropathy and constriction of the visual field. Behavioral tests for POAG target retinal ganglion cell (RGC) classes that have reduced redundancy or that might be selectively damaged, but these tests cannot differentiate dysfunctional from nonfunctional RGC inputs to motion sensors. In this study, a signal-to-noise motion-sensitivity task was used to investigate the sources of motion-sensitivity loss in patients with POAG.
An equivalent noise paradigm was used to investigate sensitivity to the direction of radial optic flow patterns across the visual field in visually normal observers and patients with POAG. Internal noise and sampling efficiency were estimated from the direction of heading contrast-discrimination thresholds as a function of the level of added external noise.
Contrast sensitivity to optic flow fell with retinal eccentricity for all observers, and decreased with both age and POAG. Equivalent noise analysis showed that the fall-off with eccentricity was primarily due to reduced sampling efficiency with relatively little increase in the level of internal noise and that the fall-off with age was attributable to both sources of error. Compared with age-matched control observers, patients with POAG have similar levels of internal noise but significantly lower sampling efficiency at all retinal loci.
Motion-sensitivity losses with age, eccentricity, and POAG can arise from higher levels of internal noise and lower sampling efficiency. The central and peripheral glaucomatous neuropathy is mostly attributable to a reduction in sampling efficiency, suggesting that RGCs are nonfunctional rather than dysfunctional in this condition.
原发性开角型青光眼（POAG）是成人不可逆性失明的主要原因，其特征为进行性视神经病变和视野缩窄。针对POAG的行为测试以冗余度降低或可能被选择性损伤的视网膜神经节细胞（RGC）类别为目标，但这些测试无法区分输入到运动传感器的功能失调与无功能的RGC。在本研究中，使用了一种信噪比运动敏感性任务来调查POAG患者运动敏感性丧失的来源。
采用等效噪声范式来研究视力正常的观察者和POAG患者对整个视野中径向光流模式方向的敏感性。根据航向对比度辨别阈值的方向作为外加外部噪声水平的函数来估计内部噪声和采样效率。
所有观察者对光流的对比度敏感性均随视网膜离心率下降，且随年龄和POAG病情加重而降低。等效噪声分析表明，离心率导致的下降主要是由于采样效率降低，内部噪声水平增加相对较少，而年龄导致的下降归因于两种误差来源。与年龄匹配的对照观察者相比，POAG患者的内部噪声水平相似，但在所有视网膜位点的采样效率显著较低。
年龄、离心率和POAG导致的运动敏感性丧失可能源于更高水平的内部噪声和更低的采样效率。青光眼性中央和周边神经病变主要归因于采样效率降低，这表明在此情况下RGC是无功能的而非功能失调。
