When a child is born, the human eye is very small, and the diameter of the eye, i.e., the eye axis, is also very small, so newborns are farsighted because the eye is small and objects are imaged behind the retina through the refractive system of the eye. As the body grows and develops, the eye becomes larger, the eye axis becomes longer, and the visual axis gradually approaches the normal adult eye axis of 23~24mm, turning into an orthoptic eye. Basically, the development of the eye is divided into two periods: the rapid development period of the eye: from birth to 3 years old, when the eye axis develops rapidly from 16mm to 19.5mm, which is a sensitive period for the development of visual function; the slow development period: from 3 years old to 18 years old, when the eye axis of 19.5mm gradually develops to 23mm~24mm; if the eye axis does not reach 23mm, hyperopia is formed; if the eye continues to grow, the eye axis continues to become longer and objects become orthoptic. If the eye continues to grow, the eye axis will continue to grow and objects will be imaged in front of the retina through the refractive system of the eye, resulting in myopia and 300 degrees of myopia for every additional 1mm. Therefore, children’s refractive error and naked eye vision are different at different ages. Therefore, most parents believe that “a child’s visual acuity less than 1.0 is poor vision” is wrong. Since hyperopia can be compensated for by a child’s strong lens accommodation, we use a method that paralyzes the ciliary muscle to remove the adjustment of the lens and check the true refractive status – called “pupil dilation”. A 10 year old child with a naked eye vision of 0.8, which was considered normal by the school, was found to have a refractive error of -0.25DS to 1.2 by dilated pupillometry, which indicates that the normal refractive error is +0.75D, but the actual refractive error is -0.25DS, indicating that as the eye develops, the eye axis continues to grow. eye axis continues to grow, this child is bound to develop myopia later! At this point, although myopia is not currently occurring, parents should pay attention to it immediately and give their children good myopia prevention. Therefore, through such examinations, we can detect the “first signs of myopia” and intervene early. There are also some cases where the visual acuity is normal, but it is actually a special type of refractive error. Astigmatism: Some astigmatic eyes with low degrees (2.00DC) or less can improve their naked eye vision by “squinting”. 2. Farsightedness and visual fatigue: Farsightedness can be compensated by the adjustment of the lens, so it is often not detected by general vision examinations. However, medium to high hyperopia is often accompanied by visual fatigue, which can be detected and dealt with through standardized optometric examinations. 3, cone cornea: early and eccentric cone cornea does not affect vision at all, simple visual acuity examination can not be found, often resulting in the case of delayed disease. We once unintentionally found a cone cornea teenager who accompanied his mother to get glasses, his naked eye visual acuity was 1.0, but we found a typical cone in the process of optometry, and corneal topography further confirmed the diagnosis. We promptly explained and communicated to the parents, and promptly treated the child with RGP, and the cone changed little during the 2-year follow-up. Recent studies have shown a high incidence of cone corneas, with a prevalence of 1/2000 in Asia; it is receiving more and more attention. The majority of patients with cone corneas are found in the process of optometry, so optometric professionals should have more knowledge to avoid delaying the condition of patients. To sum up, children of school age should be examined regardless of their visual acuity! This is the basis for establishing a refractive developmental profile and is the foundation for myopia prevention.