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V. Dobson, J.M. Miller, D.L. Sherrill, E.M. Harvey; Stability of Astigmatism in Native American Preschool Children . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4773.
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Purpose: To examine the stability of astigmatism in a preschool population in which there is a high prevalence of astigmatism. Methods: Subjects were 208 children who were participants in the Tohono O'Odham Head Start program. All were >3 and <5 years of age at the first test session. Refractive error was measured using cycloplegic (cyclopentolate 2%, followed by cyclopentolate 1%) autorefraction (Nikon Retinomax K+) on a minimum of 3 and a maximum of 6 occasions (mean = 3.7), over an average period of 1.4 years (minimum=0.6 year, maximum=2.5 years). Test-retest variability in autorefractor results were calculated based on data from 99 test-retest comparisons from 73 children who were tested twice in at least one test session. These variability results were used in Monte Carlo simulations to generate a 95% confidence interval on the slope describing the change in diopters of cylinder per year for each subject, in order to determine whether this slope differed significantly from zero. Data are reported for the right eye of each subject. Results: For the 208 subjects, mean cylinder was 1.27 D (SD=1.14, median= 0.75 D) at the first refraction and 1.30 D (SD=1.23, median=0.75 D) at the final refraction. Examination of slope data showed that 16 children (7.7%) showed a significant decrease in astigmatism, 166 (79.8%) showed no change in astigmatism, and 26 (12.5%) showed a significant increase in astigmatism. Multinomial logistic regression with slope categorized as increasing or decreasing (as compared to stable) showed that increasing or decreasing slopes were not related to age at first refraction, time between first and last refraction, or gender. Logistic regression showed that subjects with high baseline astigmatism (>1.50 D) were more likely than subjects with no-to-low astigmatism (<1.50 D) to have increasing slopes over time (odds ratio=3.37, p=0.006). Among subjects with high baseline astigmatism (>1.50 D), 15/69 (21.7%) showed increasing slopes, compared to 11/139 (7.9%) of those with no-to-low astigmatism (X2=8.06, p=0.005). Average change was 0.04 D/year (SD=0.36) in the high astigmatism group versus 0.02 D/year (SD=0.18) in the no-to-low astigmatism group. This difference was not significant. Conclusions: Preschool children with high astigmatism are more likely to show an increase in astigmatism during the preschool years than are preschool children with little or no astigmatism. However, the increase is small and not clinically significant.
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