Abstract
Purpose::
To determine the effects of eyeglass wear on best-corrected grating acuity (GA) and meridional differences in GA in astigmatic school-age children.
Methods::
K-6th grade Native American children from a Tribe with a high prevalence of astigmatism underwent eye examination and cycloplegic autorefraction (Nikon Retinomax K+), confirmed by retinoscopy. Baseline GA for horizontal and vertical stimuli was tested while children (non-cyclopleged) wore best correction. Children who met criteria for eyeglass prescription (uncorrected acuity worse than 20/20 and myopia ≥ 0.75 D or hyperopia ≥ 2.50 D in either meridian, and/or astigmatism ≥ 1.00 D, and/or anisometropia ≥ 1.50 D) were dispensed their glasses during the baseline GA testing session. Approximately 6 weeks later, best-corrected GA for horizontal and vertical stimuli was again measured. Analyses included data from children who had no ocular abnormalities or anisometropia (>1.50D), met the criteria for either the control group (right and left eye astigmatism < 0.75 D) or the astigmatic group (right eye astigmatism ≥ 1.00 D, axis 90° ± 15°), and completed GA testing at baseline and 6 weeks. Analyses examined change in best-corrected GA from baseline to 6 weeks, as well as effects of type of astigmatism (with-the-rule hyperopic (HA) vs. with-the-rule myopic or mixed (M/MA)) and age (younger cohort (< 8 years) vs older cohort (≥ 8 years).
Results::
756 children met the inclusion criteria. At baseline, astigmats (HA (n=150) and M/MA (n=162)) had significantly poorer vertical and horizontal GA than non-astigmats (n=444) (ps < 0.001). HA (p < 0.03) and M/MA (p < 0.001) groups had meridional amblyopia (MA) at baseline (horizontal better than vertical for HA, vertical better than horizontal for M/MA). Both HA and M/MA groups had significantly greater improvement in vertical and horizontal GA over the 6-week treatment interval than did the control group (ps< 0.03), but at 6 weeks, astigmats (HA and M/MA) still had significantly poorer vertical and horizontal GA than non-astigmats (ps < 0.002), and the M/MA group still showed evidence of MA (p < 0.001). There were no significant effects of age.
Conclusions::
Eyeglass wear resulted in significant improvement in GA over a 6-week treatment interval. Treatment effects were not influenced by subject age; there was no evidence that older children were less responsive to treatment. Although significant improvement was observed, astigmats still showed significantly reduced acuity after 6 weeks.
Keywords: visual acuity • amblyopia • astigmatism