[Risk factors for reduced visual acuity in female junior high school students: findings of a cross-sectional study]

The purpose was to explore the risk factors for reduced visual acuity in female junior high school students that are relevant to their living habits/environment.

A cross-sectional survey was conducted to collect data on the living habits/environment and visual acuity of female junior high school students. All the variables measured in the study were categorized into multiple, mostly two, categories, since distributions of data that are obtained at school medical examinations are often right-skewed with possible outliers; in particular, application of accurate measurement of visual acuity such as the method of refractive power was not feasible. Multiple logistic regression was employed in the analysis of data, incorporating the graphical modelling technique. Akaike Information Criteria (AIC) was used to select the best model fit for the data.

The odds ratio for students watching TV from less than a 2 m distance relative to more than 2 m was 2.08 (95%CI 1.23-3.50) and statistically significant, after adjustment for the study time at home/cram school, reading time, sleeping time, and use of glasses/contact lenses by parents/siblings. On the other hand, after the same adjustment, the odds ratio for students watching the TV for 2 h or more relative to those watching the TV for less than 2 h was close to unity and not even selected in the final model. The results also indicated that study time at home/cram school, reading time, and use of glasses/contact lenses by parents/siblings are significantly associated with reduced visual acuity. The risks of combinations of these variables were evaluated by means of the odds ratios.

We found several risk factors that are responsible for reduced visual acuity in female junior high school students. It is considered that the distance of TV viewing is the most important and yet relatively amenable to intervention for improvement to avoid reduction in visual acuity. Multivariate evaluation of the risks for visual acuity decrease was possible by means of odds ratios. Concrete suggestions can thus be made to female junior high school students to prevent decrease of visual acuity by changing the living habits/environment.