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EM Harvey, V Dobson, JM Miller; Below Normal Best-Corrected Grating Acuity Across Stimulus Orientation in Children With High Astigmatism . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4692.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Astigmatism in early childhood results in visual deprivation that can lead to the development of meridional amblyopia, a difference in best-corrected grating acuity (BCGA) for orthogonally-oriented gratings. The purpose of the present study was to determine if grade-school children with astigmatism show evidence of meridional differences in BCGA, and to determine if they show reduced BCGA across stimulus orientations in comparison to non-astigmatic children. Methods: Subjects were 111 children in grades K-8 who attend school on the Tohono O’Odham reservation. Previous research has documented a high prevalence of astigmatism in Tohono O’Odham children. Children were tested while wearing best correction, determined by cycloplegic refraction with refinement. BCGA for horizontal, vertical, and oblique lines was measured for each child’s right eye. Subjects were assigned to one of three groups based on their right eye refractive error: control group (cyl < 1.00 D, [n=75]), myopic/mixed astigmatism group (M/MA, sph < 0 D, plus cyl ≷1D, [n=24]), or hyoperopic astigmatism group (HA, sph ≷ 0 D, plus cyl ≷1 D, [n=12]). Astigmatism was with-the-rule in all MA/M and HA children. For M/MA group, horizontal lines are in poorer focus than vertical lines when uncorrected, and therefore the M/MA group should show greater BCGA deficits for horizontal than vertical stimuli if meridional amblyopia is present. The HA group can accommodate to bring either horizontal or vertical lines into focus when uncorrected and may be less likely to show meridional differences in BCGA. Results: Children in the M/MA group showed meridional amblyopia: mean horizontal BCGA poorer than vertical BCGA (mean difference 0.1 log unit (l.u.), p < 0.008). There was no evidence of meridional amblyopia in the HA group (p = 0.84). In comparison to the control group, the M/MA group showed significant deficits for horizontal and oblique BCGA (mean deficits 0.15 and 0.14 l.u., ps < 0.01), and vertical BCGA deficits neared significance (mean deficit 0.06 l.u., p < 0.07). In the HA group, there were significant deficits for horizontal BCGA (mean deficit 0.14 l.u., p < 0.04) and for oblique BCGA (mean deficit 0.22 l.u., p < 0.01), and vertical BCGA deficits neared significance (0.16 l.u., p < 0.07). Conclusion: Only the M/MA group had meridional amblyopia. However, the M/MA and HA groups both showed evidence of below-normal BCGA for all 3 stimulus orientations. Further work focusing on the nature of visual deficits associated with amblyopia in children with astigmatism is in progress.
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