7～16岁学生不同对比度视力的观察

Contrast visual acuity in the 7 - 16 years old students

目的研究7-16岁学生不同对比度下的视力（CVA）及不同对比度、年龄和性别对CVA的影响，评估在学生体检时引入低对比度视力测量的重要性。方法横断面研究。入选标准：年龄7-16岁学生，单眼裸眼视力≥1．0。共入选299名学生，将学生分为7-10岁、11-13岁和14-16岁3个年龄组。对受检者先行视力及眼部检查，然后使用电子视力测量仪MFVA-200检测对比度分别为100％标高及10％标低下的CVA。结果随着MFVA-200检查时对比度的下降，各年龄组受检者的右眼和左眼的CVA均有下降趋势，差异有统计学意义（t右眼=56．28，t左眼=63．93，P值均〈0．01）；在100％对比度下，3个年龄组间CVA差异无统计学意义（右眼CVA：F100=1．74，P=0．18；左眼CVA：F100=1．73，P=0．18），在标低10％对比度下，3个年龄组间CVA差异有统计学意义（右眼CYA：F10：4．59，P=0．01；左眼CVA：F10=5．65，P=0．004），右眼7-10岁、11-13岁和14-16岁3个年龄组CVA分别为（0．53±0．14）、（0．50±0．14）和（0．46±0．15），左眼分别为（0．53±0．16）、（0．49±0．15）和（0．45±0．15）；男性和女性在标高和标低对比度下，男性CVA值均高于女性，差异有统计学意义（右眼CVA：t100=3．67，P〈0．001；t10=2．54，P〈0．01；左眼CVA：t100=3．64，P〈0．001；t10=3．83，P〈0．001）。结论7-16岁学生随着对比度的下降，视力也出现下降趋势，高对比度视力年龄组间无差异的学生，在低对比度下年龄较大组视力差于年龄较小组，同-对比度下男性CVA好于女性。对于近视高发年龄段的学生，在体检时引入对比度视力的测量是十分重要的。

Objective To evaluate the contrast visual acuity （CVA） in Chinese 7 - 16 years old students and to study the effects of different contrast, age and sex on CVA. Methods It was a cross-sectional study. We selected two hundreds and ninety-nine students with age from 7 - 16 years old and naked monocula visual acuity equal or more than 1.0. According to the grade, we divided them to three groups： 7 - 10 years old group, 11- 13 years old group and 14 - 16 years old group. After visual acuity and eye examination, the CVA was measured on the instrument MFVA- 200 in the different contrast （ 100% and 10% ）. Results In the 7 - 16 years old students group, CVA was significantly decreased with the decrease of the contrast （tOD = 56.28,P 〈 0.01; tos = 63.93 ,P 〈 0.01 ） ;CVA in the high contrast was similar among the 3 age groups （ F100%CVAOD= 1.74 ,P = 0.18 ; F100%CVAOS = 1.73 ,P = 0.18 ）. CVA in the low contrast was significantly different among the 3 age groups （F10%CVAOD = 4. 59 ,P 〈 0.01; F10%CVAOS = 5.65 ,P 〈 0.01 ）. The mean value and standard deviation of CVA of the fight eye was 0.53 -0. 14 in the 7 - 10 age group,0.50±0.14 in the 11 - 13 age group and 0.46 -0.15 in the 14 - 16 age group. The mean value and standard deviation of CVA of the left eye was 0.53 ± 0.16 in the 7 - 10 age group, 0.49 -0.15 in the 11 - 13 age group and 0.45 ±0.15 in the 14 - 16 age group. CVA of the high or low contrast was a significantly difference between male and female（ t100%CVAOD= 3.69, P 〈 0. 001 ; t10%CVAOD =2.54,P〈0.01;t100%CVAOs=3.64,P〈0.001; t10%CVAOS=3.83,P〈0.001）. Conclusions In the7-16 years old students, CVA was significantly decreased with the decrease of the contrast;In the low contrast, the CVA of the older group was poorer than that of the younger group, however the CVA in the high contrast was similar in the 3 age groups. In the same contrast, CVA of male is better than that of female. The measurement of CVA was very important in the eye examination of students with the age of myopia.