... of myopia 17.42% and desire to reduce to 7.5% with α = 0.05, β = 0.2. The sample size for each group are 173 students. Due to the intervention study is conducted in 2 years, to ensure that ... intervention group 1 (100.3%). Myopia ratio in the intervention group 1 reduces to 4%, intervention groups 2 reduces to 4.6%, control groups increase 11% and 12%. The incidence of myopia in ... 2009 25.5 Ho Chi Minh HCM eye institution. 1994 9.75 Ho Chi Minh Le Thi Thanh Xuyen 2002 17.20 Ho Chi Minh Le Thi Thanh Xuyen 2006 38.88 Thai Nguyen Vu Quang Dzung 2002 8.9 Thai Nguyen (data...