two articles per month were sent to the parent/primary caregiver for acceptance of the intervention, and one month after the intervention began, an"Expert said" video intervention was added, at the beginning of each month, a video was posted for them to learn; three months after the start of the intervention, the wechat message intervention was added, and relevant knowledge about myopia prevention and control was sent to the wechat group every Tuesday morning; nine months after the start of the intervention, increase the text message intervention, send text messages every Friday evening to remind children of the weekend outdoor activities. In addition, live broadcasts will be held in March September and June 6 to answer parents' questions and concerns.

No intervention of any kind

The Digital Intervention Programme for parents/primary caregivers is primarily a digital intervention to address the attitudes, knowledge and actions of parents or primary caregivers of pre-school children regarding the prevention and control of myopia.

The scale was used to assess the prevention and control of myopia health literacy of parents/primary caregivers, including 3 dimensions, 6 aspects and 31 items, each with 3 or 5 options. The forward score was 1,2,3,4,5(1,2,3) , and the reverse score was 5,4,3,2,1(3,2,1) . The scale scores ranged from 0 to 102, the higher the score, the higher the health literacy of prevention and control of myopia.

Myopia screening includes Naked Eye Far Vision Examination, computer optometry and axial length measurement.In the state of non-ciliary paralysis, SE ≤ -0.50 D, visual acuity ≤4.7 at 3 years old, 4.8 at 4 years old, 4.9 at 5 years old, and less than 5.0 in the naked eye of children and adolescents over 6 years old were considered as screening myopia.

BMI = weight (kg)/[ height (m)]2. The standard deviation method was used to evaluate the physical growth of children（WS/T 423-2022）, + 1 SD≤ age BMI ≤ + 2 SD was defined as overweight, + 2 SD ≤ age BMI≤ + 3 SD was defined as Obesity.

The mental health status of preschool children was evaluated by Strength and Difficulties Questionnaire, SDQ，SDQ includes 5 dimensions: emotional symptoms, conduct problems, hyperactivity problems, peer interaction problems and prosocial behaviors.The questionnaire was scored on a 3-point scale, and was evaluated from non-conformity (0 points) to full conformity (2 points) . The scale scores ranged from 0 to 40, the higher the score, the more serious the emotional and behavioral problems.