Niwa K, Tokoro T
Department of Ophthalmology, Tokyo Medical and Dental University, School of Medicine, Japan.
Optom Vis Sci. 1998 Mar;75(3):227-32. doi: 10.1097/00006324-199803000-00029.
We investigated the influence of spatial distribution of retinal image with blur on the waveform of microfluctuations in accommodation.
We studied changes in accommodation in 8 young emmetropic subjects (21.88 +/- 2.36 years old), who viewed monocularly a target with the natural pupil. The spatial frequency of the target was varied from 0.85 to 15 cpd in 7 steps, and the blur intensity was increased in 7 steps to obtain a Gaussian distribution of retinal image. Continuous accommodation signals were recorded using an eye-tracking infrared optometer with a sampling frequency of 40.98 Hz, and analyzed with a fast Fourier transform (FFT) analyzer. The power spectra of the low frequency component (LFC, < 0.6 Hz) and the high frequency component (HFC) at approximately 1.9 Hz were calculated for each target with a frequency resolution of 0.02 Hz.
Microfluctuations in accommodation increased as the blur was increased and decreased at further increases in blur intensity level. Microfluctuations peaked at a lower blur level as the spatial frequency was increased. Power spectral analysis revealed that these changes in the microfluctuations could be attributed mainly to increases of power in the LFC.
Blurring of the edge and reduction in contrast provided accommodative cues, inducing microfluctuations in accommodation, and the LFC increased as the target sharpness was reduced, possibly in an attempt by the accommodation system to maintain the sharpness of the retinal image under poor stimulus conditions. However, when the blur level was increased, the amount of blur was indistinguishable and microfluctuations in accommodation decreased.
我们研究了具有模糊效果的视网膜图像空间分布对调节过程中微波动波形的影响。
我们对8名年轻正视眼受试者（21.88±2.36岁）进行了研究，他们单眼通过自然瞳孔观察目标。目标的空间频率以7个步长从0.85变化到15周/度，模糊强度以7个步长增加，以获得视网膜图像的高斯分布。使用采样频率为40.98Hz的眼动追踪红外验光仪记录连续的调节信号，并通过快速傅里叶变换（FFT）分析仪进行分析。对于每个目标，以0.02Hz的频率分辨率计算低频成分（LFC，<0.6Hz）和大约1.9Hz处的高频成分（HFC）的功率谱。
随着模糊程度的增加，调节过程中的微波动增加，而在模糊强度水平进一步增加时微波动减少。随着空间频率的增加，微波动在较低的模糊水平达到峰值。功率谱分析表明，微波动的这些变化主要可归因于LFC功率的增加。
边缘模糊和对比度降低提供了调节线索，诱导调节过程中的微波动，并且随着目标清晰度的降低LFC增加，这可能是调节系统试图在不良刺激条件下维持视网膜图像清晰度的一种尝试。然而，当模糊水平增加时，模糊量变得难以区分，调节过程中的微波动减少。
