Definition of amblyopia: In 1996, the National Amblyopia Prevention and Control Group defined amblyopia as a condition in which the distance visual acuity is ≤0.8 and cannot be corrected due to functional factors without obvious organic lesions. The definition of amblyopia by consensus of the Strabismus and Pediatric Ophthalmology Group of the Chinese Medical Association Ophthalmology Branch in 2010: The best corrected visual acuity of one or both eyes during visual development due to monocular strabismus, uncorrected refractive aberration and high refractive error and form deprivation is lower than the corresponding age visual acuity or the difference in visual acuity of both eyes is 2 lines or more. Visual acuity examination: different visual acuity charts are recommended for different ages; graphic visual acuity charts are recommended for 3-5 years old, VEP etc. can be used for less than 3 years old; single letter visual acuity chart examination; qualitative examination of the difference in visual acuity between the two eyes should be emphasized. Amblyopia classification: (a) Strabismic amblyopia: Amblyopia is formed by monocular strabismus. The visual center of the brain actively inhibits the visual impulses transmitted from the strabismic eye, resulting in long-term inhibition of macular function and the formation of amblyopia. (b) Refractive amblyopia: The difference between the two eyes is 1.5DS for hyperopic spherical lens and 1.0DC for column lens, which can lead to amblyopia in the eye with high refractive error. (c) Refractive amblyopia: mostly occurs in people with high refractive error who have not worn refractive correction lenses. It is mainly seen in high hyperopia or astigmatism, and it is generally believed that hyperopia ≥ 5.0DS and astigmatism ≥ 2.0DC will increase the risk of amblyopia. (iv) Formal deprivation amblyopia: visual stimulus blockage caused by deprivation factors such as refractive interstitial clouding and ptosis.