方法：前瞻性研究。选取30名志愿者，年龄18～24(平均20.9±2.1)岁，男12名，女18名，根据主觉验光结果将其分为3组：远视组H(10例)、正视组E(10例)和近视组M(10例)。所有受试者配戴软性角膜接触镜在33～40cm处观看平板电脑上播放的视频图像。应用红外电脑验光仪分别在观看前、观看后30、60min测量受试者右眼远距屈光值(每次测量5次，取平均值并按等效球镜计算)。然后立即停止近距离工作，每隔5s测量右眼远距屈光度数，记录每名受试者NITM完全消退所需时间。暂时性近视度数等于该时间点的屈光度数减去用眼前的屈光度数。采用配对t检验比较同一组内屈光度变化差异，单因素方差分析用于比较不同组间屈光度变化及NITM消退时间的差异。

结果：与用眼前相比，远视组在2个时间点的屈光变化量无明显统计学差异(t=1.627，P=0.138)； 正视组与近视组均出现近视性漂移现象且各时间点的NITM差异明显，有统计学意义(正视：t=2.699，P=0.024； 近视：t=4.930，P=0.001)。在第30、60min时，近视组平均NITM值与其他两组相比差异均有统计学意义(P<0.05)，但远视组和正视组相比屈光变化量的差异无统计学意义(P>0.05)。停止近距离工作后， 三组间NITM消退时间的差异有统计学意义(F=787.983，P<0.001)。

结论：近距离工作相同时间后，与远视和正视组相比，近视组更容易诱导出NITM且消退时间明显延长，NITM可能在近视发生发展中起重要作用。

METHODS: Prospective study. Thirty subjects(aged 18-24, average 20.9±2.1, 12 males and 18 females)were recruited in this study. They were divided into 3 groups according to the subjective refraction: 10 with hyperopia(H), 10 with emmetrope(E)and 10 with myopia(M). All the subjects with soft contact lens watched videos on a panel computer at near distance(33cm～40cm). Five measurements of distance refraction in the right eye were performed by using an infrared optometer before, after 30min and 60min sustained viewing task, and the mean of 5 refractive values was recorded as spherical equivalent. Then distance refraction of right eyes was done every 5s followed by stopping near tasking until NITM was disappeared completely and the decay time of NITM was recorded for each subject. The value of NITM was the difference of refractive values between before and after near tasking. Paired-t test was used to compare the changes of refractive values in the same group. ANOVA was used to determine the differences of NITM and its decaying time among three groups.

RESULTS: Compared with pre-task, no significant refractive changes were found in hyperopic group(t=1.627,P=0.138); While subjects with emmetropia and myopia showed more myopic shifts at the two time points(t_E=2.699,P_E=0.024; t_M=4.930,P_M=0.001). With continuous viewing until the 30^th min and 60^th min, significant differences of averaged NITM were found between myopic group and other 2 groups(P<0.05), but no difference was found between hyperopic group and emmetropic group(P>0.05). Significant differences of the decay time of NITM can be seen among the three groups after near tasking(F=787.983,P<0.001).

CONCLUSION: Subjects with myopia are more susceptible to produce NITM than other 2 groups during sustained nearwork for the same time and the decaying time of NITM is longer in myopia group after near tasking, thus it is suggesting that NITM might be attributed to the development and progression of myopia.