Trends in the incidence and causes of amblyopia and strabismus among teenagers

Abstract

Purpose : To estimate the prevalence of amblyopia and predisposing factors among teenagers, and analyze time trends.

Methods : The records of 112,559 teenagers born between 1971 and 1993 were reviewed. Amblyopia was defined as best-corrected visual acuity (BCVA) of <0.67 in either eye or as an inter-ocular difference of ≥2 lines. The prevalence across birth years was analyzed. Additionally, trends in the severity as well as the potential causes of amblyopia, including anisometropia (anisohyperopia >+1.5 diopters (D), anisoastigmatism >2D, or anisomyopia >-|3D|), isoametropia (hyperopia >+4D, myopia >|-5D|, astigmatism>2D) and strabismus were examined.

Results : The prevalence of amblyopia decreased from 1.3% in subjects born before the year 1985 to 0.9% among those born after 1985 (R²=0.88, p<0.0001). This was mostly due to a decrease in unilateral amblyopia (R²=0.92, p<0.0001). Bilateral amblyopia did not significantly change over the years (p>0.05). The severity of amblyopia did not change in a specific way across the birth years, with 57-63% of subjects having mild, 22-28% moderate, and 12-15% severe amblyopia. Anisometropia ranged between 16-25% among unilateral amblyopic teenagers across the different birth years, without a significant trend (p>0.05), while strabismus ranged between 6-13% across the different birth years, with no significant trend (p>0.05). Among bilateral amblyopes there was no significant trend in isoametropia (hyperopic, myopic, or astigmatic), ranging together between 52-58% (p>0.05). The incidence of strabismus in the entire cohort decreased over the years, ranging from 1.4% in subjects born in earlier years to 0.6% in those born in the later years (R²=0.75, p<0.0001). Amblyopia occurred in 5-17% of strabismic subjects, and increased over the birth years (R²=0.93, p<0.01). The increase over the last years was mostly attributed to higher proportion of mild amblyopia (1.5-11%) in teenagers with strabismus (R²=0.73, p<0.01). Moderate amblyopia (1.5%-5%) and severe amblyopia (0.8%-5%) did not have a consistent trend over the birth years.

Conclusions : The incidence of amblyopia and strabismus in Israel decreased among teenagers over a span of two decades. Among strabismic teenagers the incidence of amblyopia increased in later years.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.