Vergence in mild traumatic brain injury: A pilot study

Abstract

Abstract-Vergence dysfunction in individuals with mild traumatic brain injury (mTBI) may have a negative effect on quality of life, functional abilities, and rehabilitative progress. In this study, we used a range of dynamic and static objective and subjective measures of vergence to assess 21 adult patients with mTBI and nearwork symptoms. The results were compared with 10 control adult subjects. With respect to dynamic parameters, responses in those with mTBI were slowed, variable, and delayed. With respect to static parameters, reduced near point of convergence and restricted near vergence ranges were found in those with mTBI. The present results provide evidence for the substantial adverse effect of mTBI on vergence function.

Effect of oculomotor rehabilitation on vergence responsivity in mild traumatic brain injury

“…This suggests improved convergence sustainability involving the slow vergence mechanism [63]. Our previous study in this area [41] found abnormal, reduced vergence adaptation in those with mTBI, which is also typically found in those without mTBI but with vergence-related dysfunction and correlated symptoms [68]. In contrast, the SS variability did not change markedly for divergence at the 1-m test distance.…”

“…More recently, a wide range of static and dynamic vergence parameters were tested in 21 visually symptomatic adult patients with mTBI (mean ±1 standard error of mean [SEM] age: 45.7 ± 3.1 yr), as related to nearwork, by the State University of New York (SUNY) acquired TBI research group [41]. Five static parameters were found to be significantly different and abnormal between the mTBI and the visually nondisabled groups: near point of convergence (NPC) break and recovery values were receded, positive fusional vergence (PFV) break and recovery values were reduced, and the stereoacuity threshold was elevated (presumably related to inaccurate vergence) in the group with mTBI [10].…”

“…All clinical measures were assessed using standardized clinical techniques [57]. All laboratory-based objective measures were performed using commercially available instrumentation with well-established test protocols developed in our laboratory for version [54], accommodation [58], and vergence [41]. All measures were noninvasive and were recorded with the subject's habitual distance correction in place.…”

“…2. Laboratory-based objective measures: Vergence dynamics to symmetric step vergence stimuli was recorded using the Power Refractor II (PRII) (Plusoptix Inc; Atlanta, Georgia) based on the principle of infrared videography and dynamic retinoscopy, with a sampling rate of 12.5 Hz (resolution: <0.9°) for binocular recording, as described elsewhere [41]. This sampling rate exceeds the Nyquist criterion [59].…”

“…Three artifact-free (free of blinks and/or saccades) convergence and three divergence responses were selected for analysis from the right eye position traces for each subject from a sample of seven to eight responses in each direction. The middle three responses were used for analysis, and the initial and final responses were omitted to avoid possible learning and fatigue effects, respectively [41]. An exponential decay function was fit to the traces, and the response amplitudes and time constants were obtained using GraphPad Prism (GraphPad Software Inc; La Jolla, California).…”