Alexander Kenneth R, Barnes Claire S, Fishman Gerald A, Pokorny Joel, Smith Vivianne C
Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 W. Taylor Street, Chicago, IL 60612, USA.
Invest Ophthalmol Vis Sci. 2004 Dec;45(12):4510-9. doi: 10.1167/iovs.04-0188.
To define the contrast sensitivity deficits of patients with retinitis pigmentosa (RP) under testing conditions designed to emphasize threshold mediation by either the magnocellular (MC) or parvocellular (PC) pathway.
Contrast sensitivity was measured with spatially localized, narrow-band test patterns at peak spatial frequencies ranging from 0.25 to 8 cycles per degree (cpd), using a steady-pedestal paradigm (brief presentation of the test stimulus against a continuously presented luminance pedestal) and a pulsed-pedestal paradigm (simultaneous brief presentation of the test stimulus and luminance pedestal) to favor the MC and PC pathways, respectively. The contrast sensitivity functions of 12 patients with RP who had visual acuities ranging between 20/12.5 and 20/40 were compared to those of 10 visually normal, age-equivalent control observers.
Five of the patients with RP who had Snellen visual acuities better than 20/25 had contrast sensitivity functions that were within the normal limits at all spatial frequencies for both testing paradigms. The other seven patients with RP had reduced contrast sensitivities for both paradigms, with the greatest reduction in sensitivity occurring at the highest spatial frequency. Their contrast sensitivity deficits were equivalent for the steady- and pulsed-pedestal paradigms.
As observed in previous studies, the degree of contrast sensitivity loss shown by the patients with RP was greatest at the highest stimulus spatial frequency. However, in comparison to prior studies of contrast discrimination in patients with RP, there was no evidence of a preferential contrast sensitivity loss within the MC pathway. This apparent discrepancy is attributed to differences in the test targets and psychophysical judgments that were used in the studies, which emphasizes the importance of task characteristics in evaluating relative deficits within the MC and PC processing streams in visual disorders.
在旨在强调由大细胞（MC）或小细胞（PC）通路进行阈值调节的测试条件下，确定视网膜色素变性（RP）患者的对比敏感度缺陷。
使用空间定位的窄带测试图案，在每度0.25至8周/度（cpd）的峰值空间频率下测量对比敏感度，分别采用稳定背景范式（将测试刺激短暂呈现于持续呈现的亮度背景上）和脉冲背景范式（同时短暂呈现测试刺激和亮度背景）来分别有利于MC和PC通路。将12名视力在20/12.5至20/40之间的RP患者的对比敏感度函数与10名年龄匹配的视力正常对照观察者的对比敏感度函数进行比较。
12名RP患者中，5名Snellen视力优于20/25的患者在两种测试范式的所有空间频率下，其对比敏感度函数均在正常范围内。其他7名RP患者在两种范式下的对比敏感度均降低，在最高空间频率处敏感度降低最为明显。他们在稳定背景和脉冲背景范式下的对比敏感度缺陷相当。
如先前研究中所观察到的，RP患者的对比敏感度损失程度在最高刺激空间频率处最大。然而，与先前关于RP患者对比辨别力的研究相比，没有证据表明MC通路内存在优先的对比敏感度损失。这种明显的差异归因于研究中使用的测试目标和心理物理学判断的差异，这强调了任务特征在评估视觉障碍中MC和PC处理流内相对缺陷方面的重要性。
Zotero 插件