Yeo Anna Chwee Hong, Atchison David A, Schmid Katrina L
Applied and Health Sciences Cluster, Singapore Polytechnic, Singapore.
Optom Vis Sci. 2013 Feb;90(2):156-63. doi: 10.1097/OPX.0b013e31827ce23a.
Inaccurate accommodation during nearwork and subsequent accommodative hysteresis may influence myopia development. Myopia is highly prevalent in Singapore; an untested theory is that Chinese children are prone to these accommodation characteristics. We measured the accuracy of accommodation responses during and nearwork-induced transient myopia (NITM) after periods spent reading Chinese and English texts.
Refractions of 40 emmetropic and 43 myopic children were measured with a free-space autorefractor for four reading tasks of 10-minute durations: Chinese (SimSun, 10.5 points) and English (Times New Roman, 12 points) texts at 25 cm and 33 cm. Accuracy was obtained by subtracting accommodation response from accommodation demand. Nearwork-induced transient myopia was obtained by subtracting pretask distance refraction from posttask refraction, and regression was determined as the time for the posttask refraction to return to pretask levels.
There were significant, but small, effects of text type (Chinese, 0.97 ± 0.32 diopters [D] vs. English, 1.00 ± 0.37 D; F1,1230 = 7.24, p = 0.007) and reading distance (33 cm, 1.01 ± 0.30 D vs. 25 cm, 0.97 ± 0.39 D; F1,1230 = 7.74, p = 0.005) on accommodation accuracy across all participants. Accuracy was similar for emmetropic and myopic children across all reading tasks. Neither text type nor reading distance had significant effects on NITM or its regression. Myopes had greater NITM (by 0.07 D) (F1,81 = 5.05, p = 0.03) that took longer (by 50s) (F1,81 = 31.08, p < 0.01) to dissipate.
Reading Chinese text caused smaller accommodative lags than reading English text, but the small differences were not clinically significant. Myopic children had significantly greater NITM and longer regression than emmetropic children for both texts. Whether differences in NITM are a cause or consequence of myopia cannot be answered from this study.
近距离工作时不准确的调节及随后的调节滞后可能会影响近视的发展。近视在新加坡非常普遍；一种未经检验的理论是，中国儿童容易出现这些调节特征。我们测量了阅读中文和英文文本后近距离工作诱发的短暂性近视（NITM）期间及之后调节反应的准确性。
使用自由空间自动验光仪对40名正视儿童和43名近视儿童进行验光，进行四项时长为10分钟的阅读任务：在25厘米和33厘米处阅读中文（宋体，10.5号）和英文（新罗马体，12号）文本。通过从调节需求中减去调节反应来获得准确性。通过从任务后验光度数中减去任务前验光度数来获得近距离工作诱发的短暂性近视，并将回归确定为任务后验光度数恢复到任务前水平的时间。
对于所有参与者而言，文本类型（中文，0.9±0.32屈光度[D]对英文，1.00±0.37 D；F1,1230 = 7.24，p = 0.007）和阅读距离（33厘米，1.01±0.30 D对25厘米，0.97±0.39 D；F1,1230 = 7.74，p = 0.005）对调节准确性有显著但较小的影响。在所有阅读任务中，正视儿童和近视儿童的准确性相似。文本类型和阅读距离对NITM及其回归均无显著影响。近视儿童的NITM更大（大0.07 D）（F1,81 = 5.05，p = 0.03），消散时间更长（长50秒）（F1,°81 = 31.08，p < 0.01）。
阅读中文文本比阅读英文文本引起的调节滞后更小，但差异较小，无临床意义。对于两种文本，近视儿童的NITM明显大于正视儿童，回归时间更长。本研究无法回答NITM的差异是近视的原因还是结果。
