方法：采用分层整群抽样方法，在长沙市共抽取12所初中和12所高中的16 843名中学生为视力筛查对象。采用灯光视力表箱检查视力，应用Epidata3.20建立数据库，用SPSS 18.0软件进行统计分析。

结果：长沙市中学生视力不良检出率为71.44%，视力不良检出率女生(74.47%)高于男生(68.20%)，差异有统计学意义(χ²=80.79，P<0.01)。总体来说，视力不良检出率随着年龄的增长而增加，相同年龄段，女生检出率显著高于男生。轻度视力不良、中度视力不良和重度视力不良检出率分别为8.64%，22.35%和40.44%，不同年龄段视力不良检出率差异具有统计学意义(P<0.01)。

结论： 保护中学生视力是一项主要的社会工程，必须动员家庭、学校及社会有关方面的共同配合，采取综合性措施。

METHODS: A total of 16 843 students, selected from 12 junior high schools and 12 senior high schools in 6 districts in Changsha city with stratified-cluster sampling method, were brought into the eyesight screening. Light visual chart case was used to test eyesight. Database was established by Epidata 3.20 software and analyzed by SPSS 18.0 statistical software.

RESULTS: Poor sight relevance ratio in middle school students in Changsha city was 71.44%, and poor sight relevant ratio in female students(74.47%)was higher than that in male(68.20%), and the difference was statistically significant(χ²=80.79,P<0.01). In general, poor sight relevance ratio was increased with the growth of age. In the same age group, poor sight relevant ratio in female students was higher than that in male. The relevance ratio of mild poor sight, middle poor sight and severe poor sight was 8.64%, 22.35% and 40.44%, respectively. The poor sight relevance ratio in different age groups was discrepant, and the difference was statistically significant(P<0.01).

CONCLUSION: It is a social engineering to protect the middle school students' sight, so we should concentrate effort from family, school and social guidance together, and then come into comprehensive measures.