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

Abstract

Significance This 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 is challenging and needs further study. Purpose Determine whether to proceed to a full-scale trial of relieving base-in prism spectacles versus refractive correction alone for children with intermittent exotropia. Methods Children 3- to <13-years-old with distance intermittent exotropia control score of ≥2 points on the Intermittent Exotropia Office Control Scale1 (0 = phoria to 5 = constant), ≥1 episode of spontaneous exotropia,16–35∆ 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 non-prism 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 non-prism). Results 57 children (mean age 6.6 ± 2.2 years; mean baseline distance control 3.5 points) received prism (N = 28) or non-prism (N = 29) spectacles. At 8-weeks, mean control was 3.6 and 3.3 points in prism (N = 25) and non-prism (N = 25) groups, respectively; adjusted difference 0.3 points (95% confidence interval -0.5 to 1.1) favoring non-prism (meeting our a priori “do not proceed” criterion). Conclusions Base-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 a favorable effect of 0.75 points or larger is unlikely. There was insufficient evidence to warrant a full-scale randomized trial.

Office‐based vergence and anti‐suppression therapy for the treatment of small‐to‐moderate angle intermittent exotropia: A randomised clinical trial

“…A recent randomised clinical trial showed that base-in prism spectacles did not yield better distance control than refractive correction alone in children with IXT. 28 Based on these previous reports, the effectiveness of OBVAT for improving the control score and the absence of self-reported adverse events associated with OBVAT in the current study, eye care practitioners should consider OBVAT as a viable, nonsurgical treatment option for IXT.…”

“…Non‐surgical management of IXT has been suggested and includes watchful observation, 27 patching, 27 prism, 28 overminus lenses 29 and vision therapy/orthoptics 30‐36 . Randomised clinical trial data are available for these options except for vision therapy/orthoptics 27‐29 .…”

“…Non‐surgical management of IXT has been suggested and includes watchful observation, 27 patching, 27 prism, 28 overminus lenses 29 and vision therapy/orthoptics 30‐36 . Randomised clinical trial data are available for these options except for vision therapy/orthoptics 27‐29 . There is some evidence that vision therapy/orthoptics is effective for treating a selected group of individuals with IXT 16,30,31,32,33,34,35,36 .…”