Two-year-old baby’s vision can usually reach 0.4 or more, but in fact, we all know that the general vision of 1.0 and 1.0 or more is called normal vision, why only 0.4 vision is not necessarily considered abnormal, because children generally to 8-9 years old, vision can develop to the level of adults, that is, after 8-9 years old, vision should be in 1.0 or 1.0 or more, 8-9 years old before It does not reach 1.0 and is not considered abnormal. Each age group has a different lower limit of visual acuity, and only when the visual acuity test results do not reach the corresponding lower limit of visual acuity for the age group can we consider that there may be a problem with visual development. Usually, a child can reach 0.2 at the age of one, 0.4 or more at the age of two, 0.5 or more at the age of three, 0.6 or more at the age of four, and 0.8 or more at the age of five and above.