The relationship between motor fusion and stereoacuity in adults with normal binocular single vision

Purpose: To explore the relationship between motor fusion and stereoacuity in adults with normal binocular single vision.Method: A sample of 31 adult participants was recruited by convenience sampling. The inclusion criteria included age 18-40 and no history of uncorrectable vision loss or strabismus. Examinations included visual acuity, orthoptic assessment and non-cycloplegic autorefraction (Canon RK-F2). Stereoacuity was performed using Precision Vision's Real Depth Stereo Test, Frisby Stereo Test, Titmus Stereo Fly Test and TNO. Prism fusion ranges were performed at 33 cm and 6 m, using an accommodative target. Written informed consent was obtained from all participants prior to the examination.Results: Participants had a mean age of 23.16 ± 2.48 years, were 80.6% female and 71% had myopia. Most were orthophoric (58.1%) at distance fixation and exophoric (67.7%) at near fixation. There was a moderate and significant correlation between distance and near convergence by prism fusion ranges (r = 0.64, p < .001). There was a moderate negative correlation between near convergence by prism fusion and stereoacuity using the Real Depth Stereo Test (r = -0.42, p = .018) and Frisby Stereo Test (r = -0.52, p = .003). However, there was no correlation between near convergence by prism fusion with Titmus (r = 0.19, p = .36) or TNO (r = -0.31, p = .1). Near divergence fusion range was not significantly correlated to any stereoacuity test (all p > .05).Conclusion: There was a significant relationship between convergence fusion range and stereoacuity measured using the Frisby and Real Depth stereo tests in this population of adults with normal binocular single vision.