Accommodative responses in children with high and low levels of astigmatism

Children with uncorrected astigmatism are often assumed to accommodate to the circle of least confusion. However, empirical evidence in children without a history of refractive correction is lacking. This study found that most children accommodate toward the anterior focal plane, with both focal planes exhibiting a lag of accommodation.

To examine accommodative responses by measuring refractive states of the eye during near viewing in children with uncorrected astigmatism without a history of refractive correction.

Participants aged 3 to <10 years with no history of refractive correction monocularly viewed a 20/250 letter at a 3-D demand (33 cm) while accommodative responses were measured using open-field autorefraction. Responses were classified based on the focal plane closest to the stimulus: anterior or posterior focal plane, or circle of least confusion. Cycloplegic autorefraction was used to classify participants as having low astigmatism (≤1.50 D) or high astigmatism (>1.50 D). Participants were further subdivided as having hyperopia (≥2.00 D), myopia (≥0.75 D), or emmetropia (less than 0.75 D myopia and 2.00 D hyperopia) based on their spherical cycloplegic refractive error. Chi-square analyses and Fisher exact tests were used to assess the association between accommodative response and cycloplegic refractive error classification.

Of the 352 participants, 316 (89.8%) had low astigmatism and 36 (10.2%) had high astigmatism. In both groups, significantly more participants were classified as being focused at the anterior focal plane (low: 98.7%; high: 83.3%) than the posterior focal plane (low: 0.6%; high: 0.0%) or circle of least confusion (low: 0.6%; high: 16.7%; p<0.001). Almost all nonhyperopic participants in the low astigmatism group (99.2%) and hyperopic participants irrespective of astigmatism magnitude (low: 100%; high: 95.2%) accommodated closer to the anterior focal plane with accommodative lags in both meridians. Most nonhyperopic participants with high astigmatism also accommodated to the anterior focal plane (66.7%) and a third to the circle of least confusion (33.3%).

In contrast to the assumption that children with astigmatism accommodate to the circle of least confusion, our findings show that most children accommodated to the anterior focal plane during near-viewing tasks, with accommodative lags in both meridians.