Naveen K. Yadav

Effect of binasal occlusion (BNO) on the visual-evoked potential (VEP) in mild traumatic brain injury (mTBI)

Primary objective: The purpose of the experiment was to assess the effect of binasal occlusion (BNO) on the visually-evoked potential (VEP) in visually-normal (VN) individuals and in those with mild traumatic brain injury (mTBI) for whom BNO frequently reduces their primary symptoms related to abnormally-increased visual motion sensitivity (VMS). Design and methods: Subjects were comprised of asymptomatic VN adults (n = 10) and individuals with mTBI (n = 10) having the symptom of VMS. Conventional full-field VEP testing was employed under two conditions: without BNO and with opaque BNO which blocked regions on either side of the VEP test stimulus. Subjective impressions were also assessed. Results: In VN, the mean VEP amplitude decreased significantly with BNO in all subjects. In contrast, in mTBI, the mean VEP amplitude increased significantly with BNO in all subjects. Latency was normal and unaffected in all cases. Repeat VEP testing in three subjects from each group revealed similar test–re-test findings. Visuomotor activities improved, with reduced symptoms, with BNO in the mTBI group. Conclusions: It is speculated that individuals with mTBI habitually attempt to suppress visual information in the near retinal periphery to reduce their abnormal VMS, with addition of the BNO negating the suppressive influence and thus producing a widespread disinhibition effect and resultant increase in VEP amplitude.

Effect of oculomotor vision rehabilitation on the visual-evoked potential and visual attention in mild traumatic brain injury

Abstract Primary objective: The purpose of the experiment was to investigate the effect of oculomotor vision rehabilitation (OVR) on the visual-evoked potential (VEP) and visual attention in the mTBI population. Research design and methods: Subjects (n = 7) were adults with a history of mild traumatic brain injury (mTBI). Each received 9 hours of OVR over a 6-week period. The effects of OVR on VEP amplitude and latency, the attention-related alpha band (8–13 Hz) power (µV2) and the clinical Visual Search and Attention Test (VSAT) were assessed before and after the OVR. Results: After the OVR, the VEP amplitude increased and its variability decreased. There was no change in VEP latency, which was normal. Alpha band power increased, as did the VSAT score, following the OVR. Conclusions: The significant changes in most test parameters suggest that OVR affects the visual system at early visuo-cortical levels, as well as other pathways which are involved in visual attention.

Effect of luminance on the visually-evoked potential in visually-normal individuals and in mTBI/concussion

Abstract Purpose: To assess quantitatively the effect of luminance on VEP amplitude and latency in visually-normals (VN) and patients with mild traumatic brain injury (mTBI). Methods: VN individuals (n = 20) and those with mTBI (n = 19) participated. Those with mTBI were assessed 1–10 years post-injury (mean = 4.97 years), with the exception of one subject. Pattern VEP testing was employed using the DIOPSYS™ NOVA–TR system, with a 74 cd m−2 baseline luminance. Luminance levels were reduced with five different neutral density (ND) filters (0.5, 1.0, 1.5, 2.0 and 2.5) and compared to the baseline response. All testing was performed under binocular-viewing conditions with full refractive correction in place. Results: In both groups, mean VEP amplitude reduced with decrease in luminance (p < 0.05). At each luminance level, the mean VEP amplitude was significantly lower in mTBI than in the VN population (p < 0.05). In both groups, the mean VEP latency increased progressively with reduction in luminance (p < 0.05), with it being significantly higher in mTBI than in the VN population (p < 0.05). Conclusions: High luminance levels produced an optimal VEP response in both populations. VEP amplitude was robust, whereas latency progressively increased in both groups as luminance decreased. The latency increase with decreased luminance was significantly larger in those with mTBI, thus suggesting that latency can be used to differentiate reliably between VN individuals and those with mTBI.

Optimization of the pattern visual evoked potential (VEP) in the visually-normal and mild traumatic brain injury (mTBI) populations

Abstract Primary objective: The purpose of this study was to assess the effect of check size (CS) and contrast (C) on VEP amplitude and latency in visually-normal (VN) and in mild traumatic brain injury (mTBI) adults to develop an optimized test protocol in each group. Research design and methods: Subjects were comprised of VN (n = 19) and individuals with mTBI (n = 16). Full-field, pattern VEP testing was employed with three different CSs (10, 20 and 40 min arc) and at two C levels (20 and 85%). Results: There was a significant effect of CS and C on the VEP amplitude and latency in both groups. The 20 min arc CS at both contrast levels produced the largest VEP amplitude, in conjunction with normative latency values, in both populations. There was a significant differential effect of CS and C on VEP responses in the visually symptomatic vs. asymptomatic mTBI sub-groups. A significant correlation was found between time since their most recent brain injury and VEP amplitude for the 20 min arc CS at low contrast. Conclusions: Use of the 20 min arc CS at both contrast levels represents an optimized clinical VEP test protocol in both the VN and mTBI groups. This protocol is rapid, high yield, and targeted for each diagnostic group.

Objective assessment of visual attention in mild traumatic brain injury (mTBI) using visual-evoked potentials (VEP)

Abstract Purpose: To quantify visual attention objectively using the visual-evoked potential (VEP) in those having mild traumatic brain injury (mTBI) with and without a self-reported attentional deficit. Research design and methods: Subjects were comprised of 16 adults with mTBI: 11 with an attentional deficit and five without. Three test conditions were used to assess the visual attentional state to quantify objectively the VEP alpha band attenuation ratio (AR) related to attention: (1) pattern VEP; (2) eyes-closed; and (3) eyes-closed number counting. The AR was calculated for both the individual and combined alpha frequencies (8–13 Hz). The objective results were compared to two subjective tests of visual and general attention (i.e. the VSAT and ASRS, respectively). Results: The AR for both the individual and combined alpha frequencies was found to be abnormal in those with mTBI having an attentional deficit. In contrast, the AR was normal in those with mTBI but without an attentional deficit. The AR correlated with the ASRS, but not with the VSAT, test scores. Conclusions: The objective and subjective tests were able to differentiate between those having mTBI with and without an attentional deficit. The proposed VEP protocol can be used in the clinic to detect and assess objectively and reliably a visual attentional deficit in the mTBI population.

Effect of binasal occlusion (BNO) and base-in prisms on the visual-evoked potential (VEP) in mild traumatic brain injury (mTBI)

Abstract Purpose: To assess quantitatively the effect and relative contribution of binasal occlusion (BNO) and base-in prisms (BI) on visually-evoked potential (VEP) responsivity in persons with mild traumatic brain injury (mTBI) and the symptom of visual motion sensitivity (VMS), as well as in visually-normal (VN) individuals. Research design and methods: Subjects were comprised of 20 VN adults and 15 adults with mTBI and VMS. There were four test conditions: (1) conventional pattern VEP, which served as the baseline comparison condition; (2) VEP with BNO alone; (3) VEP with 2 pd BI prisms before each eye; and (4) VEP with the above BNO and BI prism combination. Results: In mTBI, the mean VEP amplitude increased significantly in nearly all subjects (∼90%) with BNO alone. In contrast, in VN, it decreased significantly with BNO alone in all subjects (100%), as compared to the other test conditions. These objective findings were consistent with improvements in visual impressions and sensorimotor tasks in the group with mTBI. Latency remained within normal limits under all test conditions in both groups. Conclusions: Only the BNO condition demonstrated significant, but opposite and consistent, directional effects on the VEP amplitude in both groups. The BNO-VEP test condition may be used clinically for the objectively-based, differential diagnosis of persons suspected of having mTBI and VMS from the VNs.

The effect of retinal defocus on simple eye-hand and eye-foot reaction time in traumatic brain injury (TBI).

Abstract Primary objective: The purpose of the experiment was to assess the effect of retinal defocus on simple eye-hand (E-H) and eye-foot (E-F) reaction time (RT) in traumatic brain injury (TBI). Design and methods: Sixteen subjects with traumatic brain injury (five males and 11 females; aged 22–34 years) participated in the experiment. These were compared with 16 visually-normal, age/gender-match subjects. Retinal defocus was introduced optically (plano, +1, +2, +3, +4, +10D and +2D × 90) in the spectacle plane with binocular viewing. E-H and E-F RT were assessed binocularly using the RT-2S Simple Reaction Time Tester (Advanced Therapy Products, Glen Allen, VA). The test target colour and angular subtense simulated a conventional red/green traffic signal at 120 feet. Results: There was no significant effect (p > 0.05) of retinal defocus on either E-H or E-F RT in each population. There was a significant effect (p < 0.05) of TBI on both E-H and E-F RT as compared with the normative data, with it being longer and more variable in TBI. Each RT condition was longest in those with moderate TBI. Conclusions: Both RTs were robust to retinal defocus, thus suggesting central nervous system insensitivity for this simple RT task. However, the increased RTs and related variability found in TBI, especially in moderate TBI, have potential safety implications (e.g. driving a car, ambulating).

Binasal Occlusion (BNO), Visual Motion Sensitivity (VMS), and the Visually-Evoked Potential (VEP) in mild Traumatic Brain Injury and Traumatic Brain Injury (mTBI/TBI)

The diagnosis and treatment of the possible visual sequelae in those with traumatic brain injury (TBI) represents an important area of health care in this special population. One of their most prevalent yet elusive visual symptoms is visual motion sensitivity (VMS). In this review, we present the basic VMS phenomenon and its related symptoms, clinical studies in the area, clinical research investigations using the visual-evoked potential (VEP) as a cortical probe, and possible mechanisms and related neurophysiology that may underlie VMS. Lastly, therapeutic interventions are briefly described, as well as future directions for clinical research and patient care in those with VMS and TBI.

A Novel Computer Oculomotor Rehabilitation (COR) Program for Mild Traumatic Brain Injury (mTBI)

Individuals with traumatic brain injury (TBI) manifest a wide range of visual dysfunctions. One of the most prevalent involves the oculomotor system, which includes version, vergence, and accommodation. However, until recently, there has been no comprehensive, computer-based program for remediation of these oculomotor deficits. We present such an oculomotor rehabilitation program that has been tested in a clinical trial in patients having TBI with a high degree of success based on before-and-after objective system recordings, performance measures, and related visual symptomotology. The basic program components include a versatile stimulus package incorporating the attentional paradigm of rapid serial visual presentation (RSVP), the ability to add a visual and/or auditory distractor to the training to increase difficulty level (“task loading”), automated assessment of RSVP errors, and automated assessment of visual performance over the training period. Program limitations and future directions are also considered.