Oculomotor Vision Rehabilitation in Mild Traumatic Brain Injury: Effect on the Visual Evoked Potential (VEP) and Visual Attentional (VAT) Responsivity

Abstract

Purpose: To assess the effect of oculomotor vision rehabilitation (OVR) on the VEP amplitude and latency, as well as subjective and objective visual attention (VAT), in mild traumatic brain injury (mTBI).

Methods: Young adults with mTBI (n=7, mean = 29 years, 1-6 years post-insult) having oculomotor and VAT deficits were trained and tested. OVR included training (6 weeks, 9 hours total, 3 hours each system) of the three oculomotor systems (version, vergence, and accommodation). Pattern-VEP testing was performed before and after the successful OVR using the DIOPSYS^TM system (17H x 15V degree field size, 20' check size, 85% contrast, 74 candelas per square meter, 1 Hz temporal frequency, 20 second trials, 1 meter test distance, binocular viewing with spectacle correction). Subjective (VSAT percentile) and objective [VEP; eyes-closed alpha (8-13 Hz) power ÷ eyes-open alpha power, the attenuation ratio (AR)] (Willeford et al., 2013) VAT were also assessed before and after the OVR. Three VEP trials were averaged for each of the 2 test conditions in each subject at each test session.

Results: There was a significant increase in the group mean VEP amplitude (17.10 to 19.15 µV), and a significant decrease in its variability (1.89 to 1.03 µV), following OVR (p ≤ 0.05). Group mean VEP latency and its variability did not change significantly before and after OVR (p ≥ 0.05). There was a significant increase in VSAT percentile score (40.25 to 59.5 percentile) (p ≤ 0.05), as well as in the alpha AR for both the full alpha band (8-13 Hz), and selected sub-bands (10, 11, and 13 Hz), following OVR (p ≤ 0.05). The significant increases in VEP amplitude and the AR ratios were found in all subjects following the OVR.

Conclusions: These findings demonstrate for the first time that OVR improves neuro-cortical activity in mTBI patients. The VEP amplitude increased with reduced variability, and VAT improved both subjectively and objectively, with this latter finding being consistent with earlier subjective results (e.g., Solan et al., 2003), thus suggesting that embedded in OVR is attentional training/enhancement. Furthermore, these results demonstrate that the VEP could be used reliably and objectively to assess the effect of OVR in mTBI.

Keywords: 507 electrophysiology: clinical • 611 neuro-ophthalmology: cortical function/rehabilitation • 742 trauma