A 10-year-old child’s vision is generally considered to develop to the level of a normal person’s vision. Normal human vision is generally considered to be 5.0, or 1.0 or above as it used to be called. 8-9 year olds can in fact basically reach this standard, while children under 8-9 years old are in the developmental growth stage and may not reach 5.0, but they are not necessarily considered abnormal. Each age group has a lower limit of visual acuity, below which the child should be considered to have delayed visual development, and further tests should be done to rule out the cause and do targeted treatment. It is generally believed that the lower limit of vision is 0.5 for three-year-olds, 0.6 for 4-5-year-olds, 0.7 for six-year-olds, and 0.8 for seven-year-olds and above, so when you check your vision at each age, you should refer to the lower limit of vision in relation to your own age, rather than taking 5.1 as a standard.