Randomized Controlled Trial of Brock String Vision Therapy for Receded Near Point of Convergence Following Concussion

The objective of this study was to compare the effectiveness of Brock string vision therapy (BSVT) with usual care (UC) for receded near point of convergence (NPC) following concussion. This study employed a single-blind, randomized controlled trial design involving participants aged 11-30 years within 10 days of a concussion. Participants with receded NPC (i.e., mean NPC ≥5 cm) were randomized to either BSVT or UC. The BSVT group was prescribed BSVT exercises (5 reps, 2× daily, using ∼3 meters string with three colored beads). The UC group was prescribed symptom-specific management strategies (i.e., breaks during reading or other visual tasks) and behavioral management (e.g., sleep, hydration, diet) until follow-up (7-14 days post-enrollment). Two-way mixed effects analyses of variance examined the interaction between group (BSVT, UC) and time (enrollment, follow-up) on mean NPC (primary outcome) and secondary outcomes (e.g., Concussion Clinical Profile Screen [CP Screen]). Fifty participants were enrolled, with 25 in BSVT (age = 15.8 ± 4.1, 44% F, 84% sport-related concussion [SRC]) and 25 in UC (age = 17.9 ± 4.8, 36% F, 60% SRC). Results supported an interaction in the BSVT group for NPC (F[1, 48] = 5.3, p = 0.026, η_p² = 0.10) and CP Screen Neck (F[1, 43] = 4.9, p = 0.033, η_p² = 0.10). The BSVT group exhibited greater improvement in mean NPC distance (-8.9 cm, 95% confidence interval [CI] = -12.1, -5.7, p < 0.001) than the UC group (-3.8 cm, 95% CI = -6.9, -0.6, p = 0.02), and greater improvement in CP Screen Neck symptoms (-0.6, 95% CI, -1.1, -0.03, p = 0.039) than the UC group (0.27, 95% CI, -0.3, 0.8, p = 0.32). BSVT improved mean NPC distance compared with UC, suggesting that this simple, inexpensive, and early intervention may be effective for treating receded NPC following concussion. Trial registration: www.clinicaltrials.gov; identifier: NCT04076657.