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Kenneth Ciuffreda, Preethi Thiagarajan; Effect of oculomotor rehabilitation on vergence responsivity in mild traumatic brain injury (mTBI). Invest. Ophthalmol. Vis. Sci. 2013;54(15):1919.
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To evaluate a range of laboratory and clinical measures of vergence before and after conventional oculomotor training versus SHAM training in individuals with mTBI.
Twelve non-strabismic individuals with mTBI (mean age: 29 [± 3] years) having oculomotor-based, reading-related near vision symptoms were tested. Laboratory-based vergence dynamics to a symmetric step stimulus (targets at 1m and 0.33m) was recorded objectively using the Power Refractor II. All clinical vergence parameters were measured using conventional and standardized clinical techniques. All parameters were assessed before and after the oculomotor (step and ramp vergence training) and SHAM training (6 weeks each, 2 sessions/week, 45 minutes/session). In addition, near vision symptoms using the convergence insufficiency symptom survey (CISS) scale and subjective visual attention using the visual search and attention test (VSAT) were assessed. Significance level was p<0.05.
Mean peak velocity increased significantly following the oculomotor training for both convergence (13 to 18 deg/sec) and divergence (11.6 to 13.5 deg/sec). Concomitantly, mean time constant reduced significantly for both convergence (399 to 228 msec) and divergence (378 to 312 msec). Clinically, this increase in the response speed was consistent with a significant increase in mean vergence prism facility (5.5 to 10.2 cycles/min). The steady-state (SS) response variability for convergence reduced (0.9 to 0.75 degrees) significantly following training, but did not for divergence. Clinically, the amplitude of convergence (NPC break and recovery), positive and negative fusional amplitudes, and near stereoacuity improved significantly. In addition, individuals reported significantly reduced symptoms (~25%) and increased subjective visual attention (~55%). None of the parameters were found to change significantly following the SHAM training.
The marked improvement in vergence eye movements, both clinically and in the laboratory, following oculomotor training demonstrates considerable residual brain visual system plasticity via oculomotor learning. The improved vergence impacted positively on nearwork-related symptoms and subjective attention.
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