Three-Year Observation of Children 3 to 10 Years of Age with Untreated Intermittent Exotropia

Abstract

Purpose: To describe the course of intermittent exotropia (IXT) in children followed up without treatment for 3 years.

Design: Observation arm from randomized trial of short-term occlusion versus observation.

Participants: One hundred eighty-three children 3 to 10 years of age with previously untreated IXT and 400 seconds of arc (arcsec) or better near stereoacuity.

Methods: Participants were to receive no treatment unless deterioration criteria were met at a follow-up visit occurring at 3 months, 6 months, or 6-month intervals thereafter for 3 years.

Main outcome measures: The primary outcome was deterioration by 3 years, defined as meeting motor criterion (constant exotropia ≥10 prism diopters [Δ] at distance and near) or near stereoacuity criterion (≥2-octave decrease from best previous measure). For the primary analysis, participants also were considered to have deteriorated if treatment was prescribed without meeting either deterioration criterion.

Results: The cumulative probability of protocol-specified deterioration by 3 years was 15% (95% confidence interval, 10%-22%), but that was likely an overestimate, partly because of misclassification. Among 25 deteriorations, 2 met motor deterioration, 11 met stereoacuity deterioration, and 12 started treatment without meeting either criteria (7 for social concern, 1 for diplopia, 4 for other reasons). Among the 132 participants who completed the 3-year visit and had not been treated during the study, only 1 (<1%) met motor or stereoacuity deterioration criteria at 3 years. Of the 4 participants completing the 3-year visit who met deterioration criteria previously and had not started treatment, none still met deterioration criteria. Between the baseline and 3-year examination for these 132 patients, improvement occurred in distance and near stereoacuity (mean improvement, 0.14 and 0.14 logarithm of arcsec; P ≤ 0.001 and P ≤ 0.001, respectively), distance exotropia control (mean improvement, 0.6 points; P ≤ 0.001), and distance exodeviation magnitude (mean improvement, 2.2 Δ; P = 0.002).

Conclusions: Among children 3 to 10 years of age with IXT for whom surgery was not considered to be the immediately necessary treatment, stereoacuity deterioration or progression to constant exotropia over 3 years was uncommon, and exotropia control, stereoacuity, and magnitude of deviation remained stable or improved slightly.

Figure 1:

Cumulative Proportion with Deterioration at Any Time during 3 Years (Primary Outcome). Parentheticals indicate 95% confidence intervals.

Figure 2:

Baseline versus 3-Year Stereoacuity for Participants Who Completed the 3-Year Visit and Had Not Been Prescribed Treatment Anytime during the Study (N=132) Figure 2a shows distance stereoacuity; Figure 2b shows near stereoacuity. Center diagonal line represents the same score for baseline and 3 years. The upper diagonal line indicates worsening of two octaves (0.6 logarcsec); the lower diagonal line indicates improvement of two octaves (0.6 logarcsec).

Figure 3:

Baseline Control versus 3-Year Control for Participants Who Completed the 3-Year Visit and Had Not Been Prescribed Treatment Anytime during the Study (N=132) Figure 3a shows distance control; Figure 3b shows near control. Center diagonal line represents the same control score for baseline and 3 years. The upper diagonal line indicates worsening of 3 points on a scale between 0 (phoria) and 5 (constant) based on the 3-point threshold for real change; the lower diagonal line indicates improvement of 3 points.

Figure 4:

Baseline versus 3-Year PACT for Participants Who Completed the 3-Year Visit and Had Not Been Prescribed Treatment Anytime during the Study (N=132) Figure 4a is distance PACT; Figure 4b is near PACT. Center diagonal line represents the same PACT for baseline and 3 years. The upper diagonal line indicates worsening that exceeds published repeatability coefficients based on test-retest data (8∆ for distance PACT and 13∆ for near PACT); the lower diagonal line indicates improvement of those amounts.