What causes amblyopia?

Most amblyopia is congenital, but some amblyopia may be acquired. This is related to the cause of amblyopia. Amblyopia is mainly divided into four categories, which are also the main causes, including:

1. Strabismus amblyopia: amblyopia caused by monocular strabismus.

2. Anisometropic amblyopia: binocular hyperopic refractive error, spherical refractive power difference ≥ 1.50DS, or cylindrical refractive power difference ≥ 1.00DC, amblyopia caused by the eye with higher refractive power.

3. Refractive amblyopia: binocular amblyopia, mostly occurs in patients with high refractive error who have not worn corrective glasses [hyperopia refraction ≥ 5.00DS and (or) astigmatism ≥ 2.00DC can increase the risk of amblyopia], and the corrected visual acuity of both eyes is equal or close. It is usually diagnosed after wearing refractive correction glasses for 3 to 6 months.

4. Form deprivation amblyopia: monocular or binocular amblyopia caused by form deprivation factors such as opacities in the refractive medium (such as congenital cataracts, corneal opacities, etc.), congenital ptosis blocking the visual axis, inappropriate occlusion (acquired), etc.

Among these factors, anisometropia and amblyopia due to refractive error are indeed mostly congenital. As for strabismus, some strabismuses are present after birth, while others appear in infancy or childhood, such as accommodative esotropia or acute concomitant esotropia. Even if these strabismuses do not occur after birth, they will also cause amblyopia if they occur before the child is 6 years old, when the visual development is not mature. As for the factors of form deprivation, if it is a congenital disease such as congenital cataract or congenital ptosis, the child will develop amblyopia after birth. However, if the child suffers from acquired organic lesions in the eye, ocular trauma, keratitis, etc. during the sensitive period of visual development, which affects the child's visual pathway, it will interfere with the development of the child's vision and cause acquired amblyopia.