Virtual Reality-Based Screening Tool for Distance Horizontal Fusional Vergence in Orthotropic Young Subjects: A Prospective Pilot Study.

This prospective pilot study aimed to develop and evaluate a VR-based screening tool for assessing distance fusional vergence amplitude in healthy orthotropic young adults aged 18 to 30 years. A VR-based balloon-hitting game was used to measure hitting deviation angles and total vergence amplitudes under five conditions: control (0 prism diopter [PD]), inward image rotation for 10 and 20 PD (negative fusional vergence [NFV] 10/20 groups), and outward image rotation for 10 and 20 PD (positive fusional vergence [PFV] 10/20 groups). Of the 20 subjects recruited, one was excluded due to esotropia, leaving 19 participants (mean age: 22.2 ± 2.2 years; 13 wore glasses and 3 were female). In the control group, the mean hitting deviation was 0.65 ± 0.25 PD. The PFV 10 PD group showed similar deviation (0.67 ± 0.25 PD, = 0.67), while the PFV 20 PD group had a significant increase (1.71 ± 2.0 PD, = 0.04). NFV groups demonstrated greater deviations (NFV 10 PD: 3.40 ± 2.05 PD; NFV 20 PD: 9.9 ± 2.40 PD, both < 0.01). Total vergence amplitudes were 8.65, 16.48, 6.60, and 10.05 PD for PFV 10, PFV 20, NFV 10, and NFV 20 PD, respectively. The VR-based tool enables standardized, efficient assessment of fusional vergence and shows promise for large-scale screening.