How severe does myopia, or nearsightedness, need to be for a child to be at risk for amblyopia?

The American Association for Pediatric Ophthalmology and Strabismus (AAPOS) published revised guidelines about amblyopia risk factors in 2012. AAPOS determined that the amount of myopia that puts a child at risk for amblyopia varies according to age, since the amount of myopia normally naturally lessens as a child ages and his eyes grow. For children aged 12-30 months, AAPOS guidelines consider the child at risk for myopia greater than -3.5 diopters; for children aged 31-48 months, myopia greater than -3.0 diopters is considered a risk factor for amblyopia, and for children 49 months and older, nearsightedness of more than -1.5 diopters is considered an amblyopia risk factor. iScreen Vision uses AAPOS guidelines in analyzing images and determining whether or not a child who is screened or tested for amblyopia should be referred for myopia.