The study examined the relationship between early onset of menstruation and the incidence of myopia in 468 twelve-year-old girls in Chongqing, China. The results showed that the incidence of myopia in the right eye was 82.7% in girls with early onset of menstruation (aged 11 years and earlier), while it was 72.3% in girls with late onset of menstruation. In the left eye, the prevalence of myopia in the early-onset group was 77.0%, compared to 67.3% in the normal-onset group. When moderate-to-severe myopia was used as the outcome, early onset of menstruation was significantly associated with a higher incidence of myopia in both eyes, even after controlling for other factors. The study authors concluded that additional interventions may be needed to prevent the early onset of myopia in early adolescence.