Allison I. Summers, David G. Morrison, Danielle L. Chandler, Robert J. Henderson, Angela M. Chen, David A. Leske, Kimberly R. Walker, Zhuokai Li, B. Michele Melia, Derek P. Bitner, Sudhi P. Kurup, Megan Allen, Paul H. Phillips, David L. Nash, Adriana P. Grigorian, Courtney L. Kraus, Aaron M. Miller, Jenna R. Titelbaum, Raymond T. Kraker, Jonathan M. Holmes, Susan A. Cotter,

A Pilot Randomized Clinical Trial of Base-in Relieving Prism Spectacle Treatment of Intermittent Exotropia

  • Optometry
  • Ophthalmology
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SIGNIFICANCEThis pilot randomized trial, the first to evaluate a specific base-in relieving prism treatment strategy for childhood intermittent exotropia, did not support proceeding to a full-scale clinical trial. Defining and measuring prism adaptation in children with intermittent exotropia are challenging and need further study.PURPOSEThis study aimed to determine whether to proceed to a full-scale trial of relieving base-in prism spectacles versus refractive correction alone for children with intermittent exotropia.METHODSChildren 3 years old to those younger than 13 years with distance intermittent exotropia control score of ≥2 points on the Intermittent Exotropia Office Control Scale (Strabismus 2006;14:147–150; 0 [phoria] to 5 [constant]), ≥1 episode of spontaneous exotropia, and 16 to 35∆ by prism-and-alternate-cover test, who did not fully prism adapt on a 30-minute in-office prism-adaptation test were randomized to base-in relieving prism (40% of the larger of distance and near exodeviations) or nonprism spectacles for 8 weeks. A priori criteria to conduct a full-scale trial were defined for the adjusted treatment group difference in mean distance control: “proceed” (≥0.75 points favoring prism), “uncertain” (>0 to <0.75 points favoring prism), or “do not proceed” (≥0 points favoring nonprism).RESULTSFifty-seven children (mean age, 6.6 ± 2.2 years; mean baseline distance control, 3.5 points) received prism (n = 28) or nonprism (n = 29) spectacles. At 8 weeks, mean control values were 3.6 and 3.3 points in prism (n = 25) and nonprism (n = 25) groups, respectively, with an adjusted difference of 0.3 points (95% confidence interval, −0.5 to 1.1 points) favoring nonprism (meeting our a priori “do not proceed” criterion).CONCLUSIONSBase-in prism spectacles, equal to 40% of the larger of the exodeviations at distance or near, worn for 8 weeks by 3- to 12-year-old children with intermittent exotropia did not yield better distance control than refractive correction alone, with the confidence interval indicating that a favorable effect of 0.75 points or larger is unlikely. There was insufficient evidence to warrant a full-scale randomized trial.

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