Amblyopia more common and severe in young children with higher-magnitude anisometropia

This retrospective observational study found that young children with higher magnitudes of anisometropia had a higher prevalence and greater depth of amblyopia. The condition was more common and severe in anisometropic children aged three to five years compared with their younger counterparts.

The study's authors also found that low-magnitude anisometropia in children younger than age three might not predispose them to amblyopia, whereas children aged three to five years with low-magnitude anisometropia often experienced moderate amblyopia. These findings suggest that current American Association for Pediatric Ophthalmology and Strabismus screening criteria for the detection of refractive pathology of greater than 1.5 D in children age five and younger are too stringent and should be revised for those younger than age three to recommend a follow-up examination only when anisometropic magnitude is greater than 2.5 D, the authors concluded.

To conduct the study, the authors identified 974 children with anisometropia greater than 1 D in one meridian and complete data among 199,079 children up to age 72 months screened through a statewide preschool vision photoscreening program over a nine-year period. Of those with anisometropia, 640 (65.7 percent) had amblyopia, which the authors defined as a two-line difference in verbal recognition visual acuity measured with linear Allen, HOTV, or Snellen. Forty-three percent of amblyopic children had mild amblyopia of at least a two-line but less than a four-line difference, 42 percent had moderate amblyopia of at least a four-line but less than a six line difference, and 15 percent had severe amblyopia of at least a six-line difference.

The authors found that more than 80 percent of children with less than 2 D of anisometropia had no or only mild amblyopia, but 60 percent of those with at least 4 D of anisometropia had moderate or severe amblyopia. Additionally, close to 80 percent of anisometropic children younger than three years had no or only mild amblyopia, but 70 percent of the older anisometropic children had moderate or severe amblyopia.