AUG 29, 2012
This prospective study evaluated accommodative performance as a function of spherical equivalent (SE) and astigmatic refractive error in a cross-section of infants and toddlers. It found that mature accommodative behavior is seen at 5 to 24 months of age and that poor accommodation is associated with hyperopia.
The authors used a modified bell retinoscopy (MBR) technique to measure accommodation lag and cycloplegic retinoscopy to measure refraction in 189 children aged 5 to 24 months.
Ninety-five percent of children showed lag < 1.25 D. Accommodative lag varied with refractive error: larger accommodation lags were associated with hyperopia, especially with hyperopia ≥ 4.0 D. Lag in the more hyperopic meridian increased with increasing amounts of astigmatism in children with hyperopic astigmatism, but did not vary with the amount of astigmatism in children with myopic or mixed astigmatism.
The authors write that the term lag does not mean the accommodative response is deficient. Some discrepancy between accommodative demand and accommodative response is normal. Because there are few normative data for accommodative lag in young children, and none using MBR, the 95th percentile of observed values was used in this study to define the upper limit of normal, and lags ≥ 1.25 D were considered high.
They note that SE hyperopia and with-the-rule hyperopic astigmatism coexisted, raising the question of whether these variables are independently associated with lag. Because SE hyperopia and cylinder were not correlated overall, it is unlikely that the association of lag with hyperopia is an artifact of measuring the more hyperopic meridian in astigmatic children. However, further study of larger samples of high pure spherical hyperopes would help confirm this.
They conclude these findings support the hypothesis that children with different types of astigmatism may select different accommodative strategies to minimize defocus across a range of target distances and can account for the patterns of visual acuity deficits observed in preschool children having predominantly with-the-rule astigmatism.