Objective evaluation of fusional vergence after a vision therapy protocol in typical binocular vision

Vision therapy is an effective treatment option for binocular vision and accommodative anomalies. However, its effect on typical binocular vision is less documented. The aim of this study was to evaluate objectively the change in near fusional vergence amplitudes in adults with typical binocular vision after performing a vision therapy protocol.

Thirty-four adults were randomly classified into an experimental group (EG), who underwent a vision therapy protocol for 12 weeks, and a control group (CG), who received a placebo treatment for 12 weeks (Phase 1). In Phase 2, the CG performed the same therapy protocol as the EG. Fusional vergence amplitudes were measured objectively in a haploscopic set-up using smooth and step fusional vergence tests. The break points of positive and negative fusional vergence (PFV and NFV, respectively) were determined using a custom algorithm.

After Phase 1, there were no significant differences between the groups for fusional vergences. After Phase 2, PFV and NFV increased significantly as measured with the smooth and step tests (p = 0.002 and p < 0.001 for NFV and p = 0.03 and p = 0.02 for PFV, respectively). These improvements were maintained after 1 month without any further intervention (all p > 0.05).

Based on these results, clinicians should consider that the vergence system cannot be trained beyond 2 and 5 Δ for NFV and PFV, respectively, when aiming to enhance vergence skills with vision therapy in patients without binocular dysfunctions.