JAMA Ophthalmology, April 2021
Chen et al. set out to evaluate overminus spectacle therapy for the treatment of intermittent exotropia (IXT) in children between 3 and 10 years of age. They found that 12 months of overminus therapy improved distance exotropia but was associated with increased myopic shift. Moreover, the effect on distance exotropia was not maintained after treatment was discontinued.
For this trial, the researchers enrolled 386 children (mean age, 6.3 years) with IXT, a mean distance control score of 2 or worse, and a refractive error between 1 D and –6 D. The children were randomly assigned to either:
- overminus spectacle therapy (–2.5 D for 12 months, then –1.25 D for three months, followed by nonoverminus spectacles for three months), or
- nonoverminus spectacles (corrected for astigmatism, anisometropia, and myopia) worn for 18 months.
Follow-up visits took place at six, 12, 15, and 18 months. To keep participants masked, the spectacle prescription was sealed in an envelope, and lenses were changed in both groups at the 12-and 15-month marks. The main outcome measures were the mean distance IXT control scores at 12 and 18 months. Change in refractive error from baseline to 12 months was compared between groups. At each follow-up visit, adherence with treatment was rated based on parental reports of the percentage of wear time during waking hours.
During the treatment period, spectacle wear adherence was reported as excellent (more than 75% of the time) for 149 of the 196 children in the overminus group and 144 of the 190 children in the nonoverminus group. The overall completion rate was 93% at 12 months and 86% at 18 months, with 176 of the overminus group and 155 of the nonoverminus group completing 18 months of follow-up.
At 12 months, mean distance control was better in those who wore the overminus spectacles (1.8 vs. 2.8 points; adjusted difference, –0.8; 95% confidence interval [CI], –1.0 to –0.5; p < .001). But by 18 months, that advantage had dissipated (2.4 points for the overminus group, vs. 2.7 for the nonoverminus group; adjusted difference, –0.2; 95% CI, –0.5 to 0.04; p = .09). Moreover, those in the overminus group were more likely to have a myopic shift at 12 months: Thirty-three of 189 (17%) children in this group had a shift greater than 1 D from baseline, versus two of 169 (1%) children in the nonoverminus group.
In an extension phase of this study, the researchers are collecting data on change in refractive error and axial length at 24 and 36 months. (Also see related commentary by Boon Long Quah, MBBS, MMed, in the same issue.)
The original article can be found here.