Long-term visual performance was defined as the number of correct answers of the reading comprehension test. Again, the mean answer (mean of correct answers on the 10-item comprehension test) of the 5 female and 5 male subjects were used instead of individual number of correct answers to avoid the confounding of subjects’ difference. Analysis of variance (ANOVA) and calculation of effect size (2) were conducted using Statistical Products & Service Solutions (SPSS 13.0).