Anderson Andrew John, Johnson Chris A
Discoveries in Sight, Devers Eye Institute, Portland, Oregon 97232, USA.
Invest Ophthalmol Vis Sci. 2003 Sep;44(9):4147-52. doi: 10.1167/iovs.02-1076.
The frequency-doubling technology (FDT) perimeter has no provision for introducing corrective lenses, save for the patient's spectacles, and so patients are sometimes tested in the presence of moderate levels of defocus. The effect of defocus on frequency-doubling (FD) sensitivity was determined for both the commercially available instrument and for smaller targets that may be useful in spatially localizing visual field defects. In addition, whether stimulus artifacts may be detectable in the presence of defocus was assessed.
Detection and resolution thresholds for FD stimuli, along with detection thresholds for spatially uniform flickering stimuli, were measured in normal observers in the presence of up to +6 D of defocus. In addition, the effect of defocus on the summary indices (mean deviation [MD], and pattern standard deviation [PSD]) of both the commercial FDT perimeter and a customized perimeter with smaller, higher spatial frequency targets was determined.
Thresholds for conventional FD targets (0.25 cyc/deg, 25 Hz) increased 0.1 log unit with +6 D defocus, whereas thresholds for smaller, higher spatial frequency (0.5 cyc/deg) targets increased 0.4 log unit. Despite the presence of a luminance artifact in the FD stimuli, detection, and resolution thresholds remained coincident at maximum defocus, suggesting that the artifact was not detectable. MD was significantly affected by defocus for the customized FD perimeter only, and PSD was not altered for either the conventional or customized test.
In normal observers, optical defocus has little effect on FDT perimetry sensitivity and does not make low spatial frequency artifacts detectable. Improving the spatial resolution of FDT perimetry decreases its robustness to defocus.
倍频技术（FDT）视野计除患者眼镜外，没有引入矫正镜片的装置，因此患者有时在存在中度散焦的情况下进行测试。确定了散焦对市售仪器以及对可能有助于在空间上定位视野缺损的较小目标的倍频（FD）敏感度的影响。此外，评估了在存在散焦的情况下是否可检测到刺激伪迹。
在正常观察者中，在高达 +6 D 的散焦情况下，测量了 FD 刺激的检测和分辨阈值以及空间均匀闪烁刺激的检测阈值。此外，还确定了散焦对商用 FDT 视野计和具有较小、较高空间频率目标的定制视野计的汇总指标（平均偏差 [MD] 和模式标准差 [PSD]）的影响。
传统 FD 目标（0.25 周/度，25 Hz）的阈值在 +6 D 散焦时增加 0.1 对数单位，而较小、较高空间频率（0.5 周/度）目标 的阈值增加 0.4 对数单位。尽管 FD 刺激中存在亮度伪迹，但在最大散焦时检测和分辨阈值仍然一致，这表明该伪迹不可检测。仅定制的 FD 视野计的 MD 受散焦的显著影响，而传统或定制测试的 PSD 均未改变。
在正常观察者中，光学散焦对 FDT 视野检查敏感度影响很小，并且不会使低空间频率伪迹可检测到。提高 FDT 视野检查的空间分辨率会降低其对散焦的稳健性。
