低水平视觉压力的客观测量。

Objective measurements of lower-level visual stress.

作者信息

Nahar Niru K, Sheedy James E, Hayes John, Tai Yu-Chi

机构信息

College of Optometry, The Ohio State University, Columbus, Ohio 43210, USA.

出版信息

Optom Vis Sci. 2007 Jul;84(7):620-9. doi: 10.1097/OPX.0b013e3180dc99a8.

DOI:10.1097/OPX.0b013e3180dc99a8

PMID:17632311

Abstract

PURPOSE

To determine the sensitivity of the electromyography (EMG) response of the orbicularis oculi muscle to selected lower-level visually stressful conditions to establish the extent to which it can be used as a measure of visual discomfort.

METHODS

Thirty-one subjects (18 years or older) with 20/20 vision, without history of ocular pathology, oculomotor limitation, or cognitive deficits participated in the study. Subjects read on a computer display for 27 trials of 5 min duration under different low-level asthenopic conditions. The conditions were graded levels of font size, font type, contrast, refractive error, and glare. Orbicularis oculi activity was recorded using surface EMG. Blink-free epochs of EMG data were analyzed for power for all the conditions. Blink rate for all the trials was also measured. At the end of each trial, subjects rated the severity of visual discomfort experienced while reading.

RESULTS

Conditions that benefit from squint (refractive error and glare) showed increased EMG power (p < 0.001) from the orbicularis and increased blink rate (p = 0.002), whereas those that do not benefit from squint (small font and low contrast) showed no significant EMG response and a significant decrease in blink rate (p = 0.003 and p = 0.01). All conditions resulted in significant visual discomfort; the p value for font type was 0.039 and p < 0.001 for the other conditions.

CONCLUSIONS

The results suggest that the squint-beneficial conditions are operated by a local mechanism involving contraction of the orbicularis and increase in reflex blinking, whereas those that do not benefit from squint do not engage the orbicularis and decrease blink, possibly through central inhibition of spontaneous blinking. The EMG response is a sensitive objective measure for the squint-beneficial conditions. However, for the non-squint-beneficial conditions, blink rate may be a more sensitive objective measure, although EMG with longer trial durations should be tested.

摘要

目的

确定眼轮匝肌的肌电图（EMG）反应对选定的低水平视觉应激条件的敏感性，以确定其可作为视觉不适度量指标的程度。

方法

31名视力为20/20、无眼部病理史、眼球运动受限或认知缺陷的受试者（18岁及以上）参与了该研究。受试者在计算机显示器上阅读，在不同的低水平眼疲劳条件下进行27次每次持续5分钟的试验。这些条件包括字体大小、字体类型、对比度、屈光不正和眩光的分级水平。使用表面肌电图记录眼轮匝肌活动。对肌电图数据中无眨眼的时间段进行所有条件下的功率分析。还测量了所有试验的眨眼率。在每次试验结束时，受试者对阅读时所经历的视觉不适的严重程度进行评分。

结果

得益于眯眼的条件（屈光不正和眩光）显示眼轮匝肌的肌电图功率增加（p < 0.001）且眨眼率增加（p = 0.002），而那些无益于眯眼的条件（小字体和低对比度）则未显示出显著的肌电图反应且眨眼率显著降低（p = 0.003和p = 0.01）。所有条件均导致显著的视觉不适；字体类型的p值为0.039，其他条件的p < 0.001。

结论

结果表明，得益于眯眼的条件是由一种局部机制运作的，该机制涉及眼轮匝肌收缩和反射性眨眼增加，而那些无益于眯眼的条件不会使眼轮匝肌参与且眨眼减少，可能是通过对自发眨眼的中枢抑制。肌电图反应是对得益于眯眼的条件的一种敏感的客观度量指标。然而，对于无益于眯眼的条件，眨眼率可能是一种更敏感的客观度量指标，尽管应测试更长试验持续时间的肌电图。