Definition of Amblyopia

Unilateral amblyopia was defined as a 2-line interocular difference in best-corrected VA with ≤20/32 in the worse eye and with coexisting risk factor of 1) strabismus (upon examination or history of strabismus surgery); 2) anisometropia consistent with the eye with worse VA (≥1.00 D SE anisohyperopia, ≥3.00 D SE anisomyopia, or ≥1.50 D anisoastigmatism); or 3) past or present obstruction of the visual axis (e.g. cataract, ptosis, corneal opacity). Bilateral amblyopia was defined as bilaterally decreased best-corrected VA (<20/50 for 30- to 47-month-old or <20/40 for ≥48-month-old) in the presence of bilateral ametropia (≥4.00 D SE hyperopia, ≤-6.00 D SE myopia, or ≥2.50 D astigmatism) or with evidence of visual axis obstruction of both eyes[16].