In the first large-scale randomized clinical trial to evaluate the effectiveness and safety of overminus spectacle therapy for intermittent exotropia, researchers found that children three to 10 years old exhibited improved distance exotropia control after 12 months of overminus spectacle wear. However, this treatment was associated with an increased myopic shift and its effect on distance exotropia control was not maintained after tapering off treatment for three months and examining the children three months later.

The study enrolled 386 children age three to 10 with intermittent exotropia, a mean distance control score of two or worse and a refractive error between 1.00D and -6.00D. Participants were randomly assigned to overminus spectacle therapy (n=196) or to non-overminus spectacle use (n=190) The overminused subjects wore -2.50D correction for 12 months, then -1.25D for three months, followed by non-overminus spectacles for three months.

The team reported an improved mean distance control at 12 months in participants treated with overminus spectacles compared with non-overminus spectacles (1.8 vs. 2.8 points). However, there was little or no difference in mean distance control between the groups at 18 months (2.4 vs. 2.7 points).

The myopic shift from baseline to 12 months was greater in the overminus group than the non-overminus group (-0.42D vs. -0.04D), with 33 of 189 children (17%) in the overminus group vs. two of 169 (1%) in the non-overminus group displaying a shift greater than 1.00D.

“This randomized controlled trial is the first study to provide robust evidence that overminus lens treatment is associated with a greater myopic shift, particularly in children who are already myopic before initiating treatment,” wrote Angela Chen, OD, in a Practice Update commentary. “This finding is of great importance for clinicians who routinely recommend overminus lenses to treat IXT, even as a temporary treatment before considering surgery or orthoptics.”

Chen AM, Erzurum SA, Chandler DL, et al. Overminus lens therapy for children three to 10 years of age with intermittent exotropia: a randomized clinical trial. JAMA Ophthalmol. March 4, 2021. [Epub ahead of print].