Once many parents find that their child’s visual acuity is less than 1.0, their first reaction is that there is something wrong with their child’s vision. In fact, to figure out what a child’s normal visual acuity should be, we need to understand the developmental patterns of children’s eyes, refractive state and visual acuity. When a baby is born, the eye is very small. During the period from birth to 3 years old, the length of the eye grows rapidly, from 16 to 17 mm at birth to about 20.5 mm; during the period from 3 to 18 years old, the length of the eye grows slowly, from 20.5 mm to 23.5 mm on average. As the length of the eye grows, the refractive state of the eye is also changing. The eye is highly hyperopic at birth and gradually decreases in hyperopia with age. At age 3: refraction averages +3.0 D; at age 4: +2 D; at age 5: +1.5 D; at ages 8 to 14: orthophoria is reached. Accordingly, the best corrected visual acuity of children gradually increases with age: 3 years old: 0.5-0.6; 4 years old: 0.6-0.8; 5 years old: 0.8-1.0; 6 years old: 1.0 or more. Some children with lower than average visual acuity development, but the refractive state is still within the normal range, and there are no other eye diseases, this situation does not require any treatment, close follow-up observation, the future visual acuity is likely to reach the normal level. Therefore, once parents find that their children have vision problems, they must take them for a detailed eye examination and assess them according to their age based on the examination results, not just thinking that 1.0 is normal vision.