Association Between Refractive Error Change and Overminus Lens Therapy for Childhood Intermittent Exotropia

This study is an extension of the previously published PEDIG study in 2021 titled "Overminus Lens Therapy for Children 3 to 10 Years of Age With Intermittent Exotropia: A Randomized Clinical Trial," which showed that the short-term positive effects of overminus lens therapy in improving control of intermittent exotropia (IXT) did not persist at the 18-month follow-up period, during which the child had been weaned off the overminus lens therapy. The therapy consisted of three phases. During phase one (12 months), the child was required to wear prescription glasses incorporating a −2.50 D overcorrection relative to baseline cycloplegic refraction. Phase two consisted of a 3-month duration, during which the overminus prescription lenses were reduced to −1.25 D. Phase three was a 3-month period, during which the overminus prescription lenses were eliminated.

This article presents the results obtained by extending the previous study's follow-up period from 18 months to 36 months following the cessation of treatment. It shows two important points. Firstly, the magnitude of the IXT and its control scores at 24 and 36 months did not differ between the overminus and non-overminus groups. This reinforces the previous study's conclusion that overminus lens therapy does not have a lasting positive effect on IXT. Secondly, for children in the age range studied who had already progressed to myopia, there was a higher mean increase in myopic shift during the period of overminus lens wear than experienced by the non-overminus group of comparable refractive profiles. Although the subsequent rates of myopic progression were comparable in the two groups at the 24-month and 36-month periods, the net result was that the increased myopic shift in the overminus treatment group was not transient. Therefore, the authors concluded that parents should be apprised of the risk of overminus lens therapy resulting in a higher myopic shift during the treatment period.

Given that overminus lens therapy may result in asthenopia at near, has no long-term benefit, and can result in the acceleration of myopia during the treatment period, practitioners and parents should be cautioned about its utilization. Perhaps future studies will show utility in customizing overminus lens therapy. For example, one might use lower amounts of overminus lens treatment if the accommodative convergence–to-accommodation ratio is high and/or combine overminus lens treatment with an add based on plus lens acceptance findings at near. Lastly, the use of prisms and/or vision therapy in conjunction with individualized overminus lens treatment may have a synergistic effect.