McKendrick Allison M, Anderson Andrew J, Johnson Chris A, Fortune Brad
Discoveries in Sight, Devers Eye Institute, Portland, Oregon, USA.
Invest Ophthalmol Vis Sci. 2003 Mar;44(3):1111-6. doi: 10.1167/iovs.01-1251.
To determine whether the spatial structure of the frequency doubling technology (FDT) perimetry stimulus is visible at detection-contrast threshold in normal observers and those with glaucoma and to assess its perceived spatial frequency at threshold and suprathreshold contrast.
Three subject groups were assessed: 10 young normal observers (aged <40 years), 10 older normal observers (aged >50 years), and 10 subjects with glaucoma. Detection thresholds for centrally and eccentrically presented 10 degrees squares, 0.25-cyc/deg, 25-Hz counterphase flicker sine-wave gratings were obtained by using a yes-no staircase procedure. Eccentric locations were in areas of loss of FDT sensitivity (< or =21 degrees ) in subjects with glaucoma, or at 7 degrees or 21 degrees inferonasally in normal observers. Resolution-contrast thresholds were determined by a two-alternative, forced-choice staircase procedure in which subjects selected the orientation of the grating stimulus tilted at +/-45 degrees. Perceived spatial frequency was determined by having subjects alter the spatial frequency of a temporally interleaved stationary sine-wave grating to match the FDT stimulus.
No significant difference was found between detection- and resolution-contrast thresholds, implying that spatial structure was visible at detection threshold. In general, subjects perceived the spatial structure to have a spatial frequency closer to doubled than to veridical, although the young normal subjects reported a lower apparent spatial frequency than older individuals.
When instructed as for clinical testing, subjects respond to the presence of the structure of the grating, and perceive the FDT stimulus to have a spatial frequency greater than its true spatial frequency. These findings were consistent across both normal observers and those with glaucoma, at both central and eccentric test locations.
确定在正常观察者和青光眼患者中，倍频技术（FDT）视野检查刺激的空间结构在检测对比度阈值时是否可见，并评估其在阈值和超阈值对比度下的感知空间频率。
评估了三个受试者组：10名年轻正常观察者（年龄<40岁）、10名年长正常观察者（年龄>50岁）和10名青光眼患者。通过使用是-否阶梯程序获得中心和偏心呈现的10度正方形、0.25周/度、25赫兹反相闪烁正弦波光栅的检测阈值。偏心位置在青光眼患者FDT敏感性丧失的区域（≤21度），或在正常观察者鼻下7度或21度处。分辨率对比度阈值通过二选一、强制选择阶梯程序确定，受试者在该程序中选择倾斜±45度的光栅刺激的方向。通过让受试者改变时间交错的静止正弦波光栅的空间频率以匹配FDT刺激来确定感知空间频率。
在检测对比度阈值和分辨率对比度阈值之间未发现显著差异，这意味着空间结构在检测阈值时是可见的。一般来说，受试者感知到的空间结构的空间频率更接近加倍而不是真实值，尽管年轻正常受试者报告的表观空间频率低于年长个体。
当按照临床测试的指示进行操作时，受试者对光栅结构的存在做出反应，并感知FDT刺激的空间频率大于其真实空间频率。这些发现对于正常观察者和青光眼患者在中心和偏心测试位置均一致。
