A randomized trial evaluating efficacy of overminus lenses combined with prism in the children with intermittent exotropia

BACKGROUND: To evaluate the efficacy of overminus lenses combined with prism spectacles in children of 3 to 6 years of age with intermittent exotropia (IXT). METHODS: Sixty patients with IXT were randomly assigned to the treatment and observation groups. Each group included 30 IXT children aged 3 to 6 years. The treatment group was prescribed overminus lenses of − 2.50 D incorporated with the 2 PD base-in prisms on each side. Ocular alignment, the status of binocular vision, as well as the refraction changes were carried out and followed at 1, 3, 6, and 12 months. A revised form of the Newcastle Control Score (NCS) was used to evaluate the patients’ ability to control their IXT. RESULTS: After 12 months, the mean refractive error was 1.42 ± 1.25 D, and 1.43 ± 1.12 D for the observation and the treatment group, respectively (95% CI: − 0.61 to 0.62)); the mean exotropia control score was 5.72 ± 1.28 and 1.75 ± 1.18 in the observation and the treatment group, respectively (95% CI: − 4.63 to − 3.33); the mean near stereoacuity was 2.16 ± 0.42 log arcsec and 1.91 ± 0.26 log arcsec in the observation and the treatment group, respectively (95% CI: − 0.44 to − 0.06). CONCLUSIONS: In our randomized clinical trial, overminus spectacles with prism significantly improved the control of IXT and stereopsis, by reducing the angle of strabismus in children with IXT. This treatment does not appear to cause myopia, at least in the manner used this series. A further randomized trial is warranted to assess the effect of overminus spectacles with prism after the treatment has been discontinued. TRIAL REGISTRATION: This study adheres to CONSORT 2010 guidelines. Chinese Clinical Trial Registry, ChiCTR1900025243. Registered 17 August 2019.