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E.M. Harvey, V. Dobson, J.M. Miller; Treatment of Astigmatism–Related Amblyopia: Evidence for a Sensitive Period that Extends beyond Early Childhood . Invest. Ophthalmol. Vis. Sci. 2004;45(13):2580.
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Purpose: Previous retrospective studies with small numbers of subjects have suggested that the end of sensitive period for successful eyeglass treatment of astigmatism–related amblyopia is prior to age 7 years (Cobb and McDonald, 1978, Mitchell et al., 1973). We conducted a prospective study to determine if children beyond the hypothesized end of the sensitive period demonstrate improvement in vision with eyeglass treatment of astigmatism–related amblyopia. Methods: Subjects were 418 children ranging in age from 8 to 13 years. Measurements of refractive error (subjectively refined cycloplegic autorefraction using the Nikon Retinomax K+) indicated that 35% of children had at least 1.00 D of astigmatism in the RE. On a separate day, baseline letter acuity was tested while all subjects wore their best eyeglass correction. Approximately 1 month and 1 year later, follow–up measures of best–corrected letter acuity were obtained. Subjects were assigned to one of two groups: astigmatic (RE cyl ≥ 1.00D) or control (RE and LE cyl < 0.75 D). Subjects who did not meet the criteria for either group, did not have data for all 3 acuity measures, had anisometropia, or had ocular abnormalities other than refractive error were excluded from analyses. Change in right eye best–corrected acuity from baseline to 1 month and from 1 month to 1 year was compared between groups. Results: Mean best–corrected acuity for astigmatic subjects was significantly poorer (2.4 logMAR lines) than control subjects at baseline, indicating that astigmatism–related amblyopia was present. After 1 month, the astigmatic group showed a 1 logMAR line improvement in best–corrected acuity, while the control group showed no change. Neither group showed significant change in best–corrected acuity from 1 month to 1 year. At 1 month and 1 year, mean acuity in the astigmatism–group remained significantly (1.5 logMAR lines) poorer than the control group. Conclusions: These findings suggest that the sensitive period for successful reduction in astigmatism–related amblyopia persists beyond age 7 years, since these 8– to 13–year–old children showed a significant improvement in best–corrected acuity after 1 month of eyeglass wear. Amblyopia was not eliminated, however. Failure to see complete elimination of amblyopia after 1 year could reflect reduction in plasticity in older children, or may be due in part to poor treatment compliance in some subjects.
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