Accommodative responses in children with high and low levels of astigmatism

SIGNIFICANCE: 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. PURPOSE: 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. METHODS: 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. RESULTS: 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%). CONCLUSIONS: 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.