A visual acuity of 4.9 is normal for children under 4 years of age, but for children over 4 years of age with a visual acuity of 4.9, there may be vision loss. 1. Normal situation: children under 4 years of age, the eyesight is not yet well developed, vision 4.9 is normal vision. 2. Possible vision loss: Children over 4 years old with a visual acuity of 4.9 may have vision loss. It may be caused by over-exertion of the eyes or prolonged exposure to electronic products, which requires further refractive correction; it may also be caused by eye diseases. It is recommended to have a more detailed examination and correct or treat the problem according to the specific cause. A child’s vision of 4.9 needs to be assessed according to the child’s age and various factors to determine whether the child’s vision is normal. In the process of checking the vision, the child has a tilted head and squinting performance, will also affect the results of the examination, it is recommended to repeat the examination a few times, to achieve accurate judgment, at the same time, it is recommended to establish an optometric file for the child, and regularly take the child to the eye vision checkups.