To test the hypothesis that veterans with near vision symptoms after TBI have impaired ocular convergence, as measured quantitatively by a custom virtual-reality (VR) application.

Near vision impairment is a common post-concussive symptom, but its mechanism is incompletely understood. Although It is often attributed to convergence insufficiency (CI), many individuals with TBI do not undergo detailed eye examination, and quantitative eye movement analysis is largely limited to research laboratories. The goals of this project were to develop a VR tool for assessment of convergence and near vision function, to test its feasibility, and to conduct a preliminary study to test the hypothesis that near vision symptoms after TBI are explained by CI.

We recruited 16 veterans with TBI (assessed with the OSU TBI-ID). Twelve had near vision symptoms based on a Convergence Insufficiency Symptom Survey (CISS) score ≥ 21. The TBI veterans were compared to a group of 12 asymptomatic individuals without TBI. A custom VR application was developed to detemine the near point of convergence (vrNPC). Participants tracked an object moving toward them in virtual space (6 trials each). High-speed continuous eye tracking determined the time at which the eyes diverged.

Maximum vrNPC ranged from 0° (no effective convergence) to 60.4°. There was no correlation between absolute CISS score and vrNPC (r² = 0.072, p = 0.174), nor was there a group difference in vrNPC between those with normal and abnormal CISS (p = 0.542, Wilcoxon rank-sum). There was a trend for vrNPC to be higher for TBI vs non-TBI (p = 0.064), and abnormal vrNPC (< 33°) was overrepresented for TBI (9/16 vs 1/12).

CI is common in veterans with TBI but does not explain all near vision symptoms. The CISS is non-specific and a poor predictor of convergence capacity.