Effect of office-based vergence and anti-suppression therapy on binocular vision and accommodation in small-to-moderate angle intermittent exotropia: A randomised clinical trial.

Purpose: To evaluate the short-term (1 week after completion of treatment) effect of office-based vergence and anti-suppression therapy (OBVAT) on binocular vision and accommodative function when compared to observation alone in children with small-to-moderate angle intermittent exotropia (IXT).

Methods: In this single-masked (examiner masked), two-arm, single-centre randomised clinical trial, 40 participants, 6 to <18 years of age with untreated IXT were randomly assigned to OBVAT or observation alone. Participants assigned to therapy received 16 weeks of OBVAT (60 min per visit, once per week) with home reinforcement (15 min per day, 5 days a week). Therapy included vergence, accommodation and anti-suppression techniques. This paper reports the results of clinical measures of binocular vision and accommodation, including fusional vergence, near point of convergence, vergence facility, amplitude of accommodation, the Worth 4-dot test and the Fusion Maintenance Score (FMS).

Results: Treatment group differences at the primary outcome visit significantly favoured the OBVAT group (n = 20) over the observation group (n = 16) in negative fusional vergence break point at both distance (p ≤ 0.001; r = 0.58) and near (adjusted mean difference: 12.3 Δ; 95% CI: 5.3-19.3 Δ; p = 0.001; partial eta squared: 0.28), positive fusional vergence break point at both distance (p = 0.009; r = 0.43) and near (adjusted mean difference: 20.6 Δ; 95% CI: 11.8-29.4 Δ; p ≤ 0.001; partial eta squared: 0.41), vergence facility (adjusted mean difference: 5.6 cpm; 95% CI: 1.9-9.4 cpm; p = 0.005; partial eta squared: 0.22) and the FMS (p = 0.007; r = 0.44).

Conclusions: In this randomised clinical trial of participants aged 6 to <18 years with IXT, those in the OBVAT group had a significantly better fusional vergence range, vergence facility, near Worth 4-dot test result and FMS than the observation group at the 17-week visit. The improvement in these areas further support the effectiveness of OBVAT for improving IXT.