Evidence for hypermetropia, astigmatism, and anisometropia associated with, and early glasses preventing, the development of amblyopia and accommodative esotropia

In many countries that have population-wide screening for amblyopia by measurement of visual acuity (VA), additional screening for refractive errors to prevent the development of amblyopia is being considered. We assessed the available evidence for the association between high refractive error in young children and the development of amblyopia and accommodative esotropia, and the influence of early prescription of glasses. The following search terms were used: refractive errors, amblyopia or strabismus, and children. Included were articles describing associations between high hypermetropia, astigmatism, anisometropia, and early glasses, and the development of amblyopia and accommodative esotropia. Longitudinal studies were included with children aged 6–24 months at entry, with retinoscopy in cycloplegia at least once and outcome assessed at age 3–9. Excluded were studies without a longitudinal design. In total, 5458 articles were identified. The authors of the relevant articles mainly originated from Kettering, Cambridge, Göteborg, and Columbus, Ohio, and additional studies by these research groups were added. Most studies did not determine the association, were not longitudinal, studied the accuracy of photoscreeners, the prevalence of refractive errors, or the effectiveness of screening programs. Therefore, 1 RCT, 2 controlled trials, and 13 observational cohort studies were included. For hypermetropia ≥+3.5D at 8–12 months, the odds ratio for developing amblyopia ranged between 17.09 and 141.67 (3 studies), for developing accommodative esotropia 16.13 and 22.51 (2 studies). For hypermetropia between >+2.66D and ≥+4D at 0–12 months increasing until age 3, the odds ratio for developing accommodative esotropia ranged between 5.33 and 195 (3 studies). For astigmatism ≥1.5D at 12 months, the odds ratio for developing amblyopia was 9.23 (1 study), for developing accommodative esotropia 1.42 (1 study). For astigmatism ≥1D at 12 months increasing until age 3, the odds ratio for developing amblyopia ranged between 10.13 and 141 (2 studies). For anisometropia ≥0.75D in combination with hypermetropia at 5–7 months, the odds ratio for developing accommodative esotropia was 1.31 (1 study). For early glasses at age 6–24 months, the odds ratio for developing amblyopia ranged between 0.10 and 0.79 (3 studies), for developing accommodative esotropia between 0.79 and 2 (5 studies). From our review, it seems that hypermetropia and astigmatism but not anisometropia correlate with the development of amblyopia and accommodative esotropia. The influence of early glasses seems moderate.