Amblyopia: visual development caused by monocular strabismus, uncorrected refractive error and high refractive error and form deprivation, the best corrected visual acuity of one or both eyes is lower than the corresponding age visual acuity, or the visual acuity of both eyes differs by two lines or more. The lower limit of the reference value for different ages: 0.5 for 3-5 years old, 0.7 for 6 years old and above. Amblyopia classification: 1. Strabismic amblyopia: amblyopia caused by monocular strabismus 2. Refractive parallax amblyopia: 1.5DS difference between the two eyes and 1.0DC difference between the two eyes, both can make the higher refractive power of one eye to form amblyopia. 3, refractive amblyopia: mostly occurs in patients with high refractive error who have not worn refractive correction glasses. Mainly seen in both eyes with high hyperopia or astigmatism, the best corrected visual acuity in both eyes is equal or similar. It is generally believed that hyperopia ≥ 5.00DS and astigmatism ≥ 1.0DC will increase the risk of amblyopia. 4, form deprivation amblyopia: caused by deprivation factors such as refractive interstitial clouding and ptosis, amblyopia can be unilateral or bilateral, unilateral is more serious than bilateral. Suggestions for vision screening methods: Different visual acuity scales are used for different ages, and graphic visual acuity scales are recommended for ages 3-5. For those younger than 3 years old, PL, OKN, VEP, and single letter vision charts can be used, with emphasis on qualitative examination of the difference in visual acuity between the two eyes.