Zhang Jun-Yun, Zhang Ting, Xue Feng, Liu Lei, Yu Cong
State Key Laboratory of Cognitive Neuroscience and Learning, Beijing Normal University, Beijing, China.
Invest Ophthalmol Vis Sci. 2007 May;48(5):2383-90. doi: 10.1167/iovs.06-1195.
Written Chinese contains an enormous number of characters with a wide range of spatial complexities. Consequently, the legibility of Chinese characters is expected to vary significantly, and this variability offers the challenge of deriving a simple visual function measurement for the Chinese reading population. The purpose of this study was to suggest a solution to the challenge through psychophysical studies of Chinese character legibility.
To illustrate legibility variations in Chinese characters, visual acuities for six groups of Chinese characters from low to high spatial complexities and one group of Sloan letters were determined in six normal-sighted Chinese observers. The relationship between legibility and optical defocus were then determined for the Landolt C, the Snellen E, and three groups of Chinese characters representing low, medium, and high spatial complexities in 26 normal-sighted Chinese readers.
The acuity size of Chinese characters increased steadily with stimulus complexity, though at a slower rate than would be expected if visual acuity were based on the finest details of the stimuli. The acuity size versus optical defocus functions of three Chinese character groups and the Snellen E had similar slopes and differed only by a vertical shift, depending on the optotype spatial complexity. The function of the Landolt C was significantly steeper.
The findings indicate that visual acuity assessment in Chinese readers is complicated by the spatial complexity of Chinese characters, but the fact that the Snellen E, which is the current national standard of acuity measurement in China, and Chinese characters showed similar dependence on optical defocus may indicate a potentially valid way to infer functional vision in Chinese readers with Snellen E acuity.
中文包含大量具有广泛空间复杂性的汉字。因此，汉字的易读性预计会有显著差异，而这种变异性为推导针对中文阅读人群的简单视觉功能测量方法带来了挑战。本研究的目的是通过对汉字易读性的心理物理学研究来提出应对这一挑战的解决方案。
为了说明汉字易读性的差异，在六名视力正常的中国观察者中测定了六组从低到高空间复杂性的汉字以及一组斯隆字母的视力。然后在26名视力正常的中国读者中确定了兰道环C、斯内伦E以及代表低、中、高空间复杂性的三组汉字的易读性与光学散焦之间的关系。
汉字的视力大小随着刺激复杂性的增加而稳步增加，不过其增加速度比基于刺激最精细细节的视力预期速度要慢。三组汉字和斯内伦E的视力大小与光学散焦函数具有相似的斜率，仅因视标空间复杂性而在垂直方向上有所偏移。兰道环C的函数则明显更陡。
研究结果表明，汉字的空间复杂性使中文读者的视力评估变得复杂，但中国目前视力测量国家标准的斯内伦E与汉字对光学散焦表现出相似的依赖性这一事实，可能表明了一种通过斯内伦E视力推断中文读者功能性视力的潜在有效方法。
