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Erin M Harvey, Joseph M Miller, Howard P Apple, Pavan Parashar, Deborah Apple, John Daniel Twelker, Mabel Crescioni, Tina K Leonard-Green, Amy L Davis; Accommodation patterns in astigmatic children during visual task performance.. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2741.
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© ARVO (1962-2015); The Authors (2016-present)
To test the prediction that accommodative response is dependent upon visual task demand and presence of uncorrected astigmatism.
Subjects were Tohono O’odham students who have a high prevalence of with-the-rule astigmatism. Continuous measurements of non-cycloplegic right eye (RE) spherical equivalent refractive error (M) were obtained for 26 second intervals using the Grand Seiko open field autorefractor (WAM-5500) under three task conditions: “age-appropriate text reading” (AA text, sentences with letters approx. 20/100), “near-threshold text reading” (TH text, sentences with letters 2 logMAR lines above threshold) and “video”. Students read sentences out loud during reading conditions and viewed a cartoon during the video condition. Measurements for each task were made with stimuli at near (40cm) and distance (2m). Students with myopia > 2.50D (most myopic meridian per cycloplegic refraction), ocular abnormalities, anisometropia (aniso M > 1.50, aniso Cyl > 1), or less than 7 measurements in any task/distance condition were excluded. Students were classified as low (< 1.00D), moderate (1 to < 3D) or high astigmats (≥ 3D) based on RE cycloplegic refraction. Subjects accommodating to the spherical equivalent focal plane would have M measurements approximately -2.50 at near and -0.50 D at distance. RMANOVA assessed the influence of viewing distance, task condition and astigmatism magnitude on mean M, with age as a covariate.
RMANOVA yielded a significant interaction of viewing distance, task condition and astigmatism (p < 0.001). At near and distance, mean M more closely approximated predicted M (-2.50 at near, -0.50 D at distance) in the low and moderate astigmatism groups than in the high astigmatism group for all task conditions. M was more negative and was closer to predicted for the text reading conditions than for the video conditions, and this was true for both test distances and for all astigmatism groups.
Subjects tended to under-accommodate relative to the spherical equivalent focal plane, but this effect was greatest in high astigmats, who showed high variability across subjects perhaps due to accommodation to the anterior focal plane. Overall, subjects tended to accommodate closer to the spherical equivalent plane when task demand was higher (text reading conditions). Further analyses will examine the relation between accommodation patterns and acuity development.
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