If a child is younger than 4 years old and has a visual acuity of 0.4, it is generally normal. If a child is older than 4 years old and has a visual acuity of 0.4, it is generally suggestive of an abnormality, and if it is due to myopia alone, it is generally not serious. Children’s naked eye visual acuity of 0.4, if it is due to pure myopia caused, generally suggests that myopia degree in 200 degrees or so, belongs to mild myopia, generally not serious, can be corrected through the use of corrective glasses to correct. Children with a naked eye visual acuity of 0.4, generally in myopia, often combined with astigmatism, need to be examined in an eye hospital in a timely manner, accurate optometry, so that according to the results of the choice of appropriate corrective eyeglasses. Children’s visual acuity 0.4, generally not serious, but need to be corrected in time.