The best corrected visual acuity in one or both eyes is called amblyopia when there is no obvious organic pathology in the eye, or when the visual acuity of both eyes differs by 2 lines or more, and the eye with the lower visual acuity is amblyopic. Amblyopia is basically formed during the development of the eye at a young age, and the main causes are as follows: 1. strabismus: more common (accompanied by refractive error), poor vision in the non-gaze eye of constant strabismus, in addition to strabismus can cause amblyopia or caused by amblyopia. 2. Refractive aberration: common (accompanied by strabismus), with a large difference in refractive power between the two eyes (usually a difference of 150 degrees or more). 3, Refractive interstitial clouding: such as monocular cataracts, corneal scarring, or permanent primitive vitreous hyperplasia causing preferential vision in the healthy eye, resulting in amblyopia in the affected eye. 4. Formal deprivation (monocular disuse): excessive masking in the healthy eye or long-term dilated pupil with atropine can also cause amblyopia, so regular follow-up is needed, either with short duration masking or with full correction glasses when using atropine ciliary muscle paralysis. Therefore, a variety of etiologies can lead to amblyopia in children. Amblyopia in children is usually asymptomatic and is usually detected during a monocular vision examination. Unlike myopic hyperopia, it cannot be corrected to normal vision with myopic, hyperopic, or astigmatic lenses and cannot be explained by organic pathology. It mainly affects central vision, and peripheral vision is usually normal. It is easier to recognize individual letters as opposed to whole lines of letters.