Khanani Arshad M, Brown Sandra M, Xu Ke Tom
Department of Ophthalmology and Visual Sciences, Texas Tech University Health Sciences Center, Lubbock, TX, USA.
J Cataract Refract Surg. 2004 Nov;30(11):2377-82. doi: 10.1016/j.jcrs.2004.05.027.
To investigate the contrast thresholds (CTs) in normal subjects using a high-luminance, letter-recognition task under clinically relevant testing conditions.
Texas Tech University Health Sciences System, Lubbock, Texas, USA.
Sixty normal subjects aged 20 to 49 years with a best corrected visual acuity of 20/20 or better in both eyes participated. M & S Technologies software was used to display black-on-white Sloan letters at contrast levels of 25%, 20%, 15%, 12%, and 10% through 1% in 1% decrements. The effects of age, sex, optotype size, eye dominance, ambient illumination level (bright = 625 - 630 lux; dim = <3 lux), and direction of approach to threshold were analyzed using a multivariate, ordinary, least-squares analysis.
Age and sex did not influence CTs. Ascending versus descending testing was not statistically significant (P>.5). The effects of room illumination and eye dominance were significant (P<.01). Significant differences were found between 20/30 and 20/50, 20/30 and 20/70, and 20/50 and 20/70 optotype sizes (P<.01 for all comparisons).
A commercially available, computer-based test of CTs was easy to administer and apparently easy for inexperienced subjects to perform. The results suggest criteria for detecting visual problems concerned with familiar but complex spatial-image shapes. This information might be used to assess the effects of treatments such as laser refractive surgery on recognition contrast. Further study is warranted.
在临床相关测试条件下，使用高亮度字母识别任务来研究正常受试者的对比度阈值（CTs）。
美国得克萨斯州拉伯克市的得克萨斯理工大学健康科学系统。
60名年龄在20至49岁之间、双眼最佳矫正视力为20/20或更好的正常受试者参与了研究。使用M & S Technologies软件以25%、20%、15%、12%和10%的对比度水平显示白底黑字的斯隆字母，对比度以1%的递减幅度从1%开始变化。使用多元普通最小二乘法分析年龄、性别、视标大小、眼优势、环境光照水平（明亮=625 - 630勒克斯；昏暗=<3勒克斯）以及接近阈值的方向的影响。
年龄和性别不影响对比度阈值。上升测试与下降测试无统计学显著差异（P>.5）。室内光照和眼优势的影响显著（P<.01）。在20/30与20/50、20/30与20/70以及20/50与20/70视标大小之间发现了显著差异（所有比较P<.01）。
一种基于计算机的市售对比度阈值测试易于实施，对于缺乏经验的受试者来说显然也易于操作。结果表明了检测与熟悉但复杂的空间图像形状相关的视觉问题的标准。这些信息可用于评估诸如激光屈光手术等治疗对识别对比度的影响。有必要进行进一步研究。
