Optical treatment of amblyopia in astigmatic children: the sensitive period for successful treatment.

OBJECTIVE To compare the effectiveness of eyeglass treatment of astigmatism-related amblyopia in children younger than 8 years (range, 4.75-7.99 years) versus children 8 years of age and older (range, 8.00-13.53 years) over short (6-week) and long (1-year) treatment intervals. DESIGN Prospective, interventional, comparative case-control study. PARTICIPANTS Four hundred forty-six nonastigmatic (right and left eye, <0.75 diopters [D]) and 310 astigmatic (RE, > or =1.00 D) Native American (Tohono O'odham) children in kindergarten or grades 1 through 6. INTERVENTION Eyeglass correction of refractive error, prescribed for full-time wear, in astigmatic children. MAIN OUTCOME MEASURES Amount of change in mean right-eye best-corrected letter visual acuity for treated astigmatic children versus untreated, age-matched nonastigmatic children after short (6-week) and long (1-year) treatment intervals. RESULTS Astigmatic children had significantly reduced mean best-corrected visual acuity at baseline compared to nonastigmatic children. Astigmats showed significantly greater improvement in mean best-corrected visual acuity (0.08 logarithm of the minimum angle of resolution [logMAR] unit; approximately 1 line), than the nonastigmatic children (0.01 logMAR unit) over the 6-week treatment interval. No additional treatment effect was observed between 6 weeks and 1 year. Treatment effectiveness was not dependent on age group (<8 years vs. > or =8 years) and was not influenced by previous eyeglass treatment. Despite significant improvement, mean best-corrected visual acuity in astigmatic children remained significantly poorer than in nonastigmatic children after 1 year of eyeglass treatment, even when analyses were limited to results from highly compliant children. CONCLUSIONS Sustained eyeglass correction results in significant improvement in best-corrected visual acuity in astigmatic children, including those previously believed to be beyond the sensitive period for successful treatment.