Validation of Visual Objective Biomarkers for Acute Concussion.

Objective: Despite an increase in the awareness and diagnosis of mild traumatic brain injury (mTBI), there remains a paucity of data examining the comparative efficacy of available assessments. This study aims to validate visual functions as potential biomarkers for mTBI. Methods: This case-control correlational design utilizes military personnel diagnosed with acute (≤72 h post-injury) mTBI (n = 100) and age-matched controls (n = 100) to examine the relative effectiveness of the pupillary light reflex (PLR), near point of convergence (NPC) break, King-Devick (KD) test time, and Convergence Insufficiency Symptom Survey (CISS) score to discriminate between participants with mTBI. Results: Three of the eight PLR parameters (i.e., average constriction velocity (ACV), average dilation velocity (ADV), and 75% re-dilation time; all p < 0.001) were affected in mTBI participants. Similarly, NPC break, KD test time, and CISS scores showed a statistically significant difference between groups (all p < 0.001). Area under the curve showed that ADV (0.82) and NPC (0.74) have the higher predictive values of all objective parameters. Conclusions: ADV, ACV, and NPC break are objective visual functions markedly affected in the acute mTBI group compared with controls; therefore, we proposed that they could be used as biomarkers for acute mTBI.

Visual Dysfunctions at Different Stages after Blast and Non-blast Mild Traumatic Brain Injury.

PURPOSE: To assess the prevalence of visual dysfunctions and associated symptoms in war fighters at different stages after non-blast- or blast-induced mild traumatic brain injury (mTBI). METHODS: A comprehensive retrospective review of the electronic health records of 500 U.S. military personnel with a diagnosis of deployment-related mTBI who received eye care at the Landstuhl Regional Medical Center. For analysis, the data were grouped by mechanism of injury, and each group was further divided in three subgroups based on the number of days between injury and initial eye examination. RESULTS: The data showed a high frequency of visual symptoms and visual dysfunctions. However, the prevalence of visual symptoms and visual dysfunctions did not differ significantly between mechanism of injury and postinjury stage, except for eye pain and diplopia. Among visual symptoms, binocular dysfunctions were more common, including higher near vertical phoria, reduced negative fusional vergence break at near, receded near point of convergence, decreased stereoacuity, and reduced positive relative accommodation. CONCLUSIONS: The lack of difference in terms of visual sequelae between subgroups (blast vs. nonblast) suggests that research addressing the assessment and management of mTBI visual sequelae resulting from civilian nonblast events is relevant to military personnel where combat injury results primarily from a blast event.

Assessment of a Prototype Apache Flight Eyewear.

BACKGROUND: Apache pilots needing refractive correction are issued modified HGU-4/P aviator spectacles. However, a recently published survey found field of view (FOV) dissatisfaction with the current spectacles when sighting in with a Helmet Display Unit (HDU). A current Air Force flight frame was modified in-lab and the purpose of this study was to evaluate the FOV with the current Apache flight frame vs. the modified flight frame. METHODS: Recruited were 21 Apache pilots to assess FOV under three conditions: 1) wearing the current Apache frame; 2) wearing the modified Apache frame; and 3) wearing no frame. The main outcome measure was total FOV of four quadrants tested: superior left (45°); superior right (135°); inferior right (225°); and inferior left (315°). RESULTS: No significant differences in FOV were seen between the two frames tested while wearing the current Apache helmet (P = 0.33) and the new Apache helmet (P = 0.64). However, there were significant differences in FOV between the no frame condition and the two frame conditions tested with both helmets (P < 0.001). DISCUSSION: No significant differences in FOV were seen between the two frames tested while wearing either Apache helmet. However, with both helmets there were significant differences in FOV between the no frame condition and the two frame conditions tested. This suggests that wearing no eyewear is still optimal in integrating the HDU device. With advances in contact lens technology, future research can study the viability of the latest generation of multifocal contact lenses with Apache aviators. Walsh DV, Jurek GM, McLean WE, Statz JK, Allen RL, Riggs DW. Assessment of a prototype Apache flight eyewear. Aerosp Med Hum Perform. 2016; 87(9):800-805.

Assessment of the King-Devick® (KD) test for screening acute mTBI/concussion in warfighters.

OBJECTIVES: The Department of Defense reported that 344,030 cases of traumatic brain injury (TBI) were clinically confirmed from 2000 to 2015, with mild TBI (mTBI) accounting for 82.3% of all cases. Unfortunately, warfighters with TBI are often identified only when moderate or severe head injuries have occurred, leaving more subtle mTBI cases undiagnosed. This study aims to identify and validate an eye-movement visual test for screening acute mTBI. METHODS: Two-hundred active duty military personnel were recruited to perform the King-Devick® (KD) test. Subjects were equally divided into two groups: those with diagnosed acute mTBI (≤72h) and age-matched controls. The KD test was administered twice for test-retest reliability, and the outcome measure was total cumulative time to complete each test. RESULTS: The mTBI group had approximately 36% mean slower performance time with significant differences between the groups (p<0.001) in both tests. There were significant differences between the two KD test administrations in each group, however, a strong correlation was observed between each test administration. CONCLUSIONS: Significant differences in KD test performance were seen between the acute mTBI and control groups. The results suggest the KD test can be utilized for screening acute mTBI. A validated and rapidly administered mTBI screening test with results that are easily interpreted by providers is essential in making return-to-duty decisions in the injured warfighter.

A Performance Comparison of Color Vision Tests for Military Screening.

BACKGROUND: Current color vision (CV) tests used for aviation screening in the U.S. Army only provide pass-fail results, and previous studies have shown variable sensitivity and specificity. The purpose of this study was to evaluate seven CV tests to determine an optimal CV test screener that potentially could be implemented by the U.S. Army. METHODS: There were 133 subjects [65 Color Vision Deficits (CVD), 68 Color Vision Normal (CVN)] who performed all of the tests in one setting. CVD and CVN determination was initially assessed with the Oculus anomaloscope. Each test was administered monocularly and according to the test protocol. The main outcome measures were test sensitivity, specificity, and administration time (automated tests). RESULTS: Three of the four Pseudoisochromatic Plate (PIP) tests had a sensitivity/specificity > 0.90 OD/OS, whereas the FALANT tests had a sensitivity/specificity > 0.80 OD/OS. The Cone Contrast Test (CCT) demonstrated sensitivity/specificity > 0.90 OD/OS, whereas the Color Assessment and Diagnosis (CAD) test demonstrated sensitivity/specificity > 0.85 OD/OS. Comparison with the anomaloscope ("gold standard") revealed no significant difference of sensitivity and specificity OD/OS with the CCT, Dvorine PIP, and PIPC tests. Finally, the CCT administration time was significantly faster than the CAD test. DISCUSSION: The current U.S. Army CV screening tests demonstrated good sensitivity and specificity, as did the automated tests. In addition, some current PIP tests (Dvorine, PIPC), and the CCT performed no worse statistically than the anomaloscope with regard to sensitivity/specificity. The CCT letter presentation is randomized and results would not be confounded by potential memorization, or fading, of book plates.

Assessment of an Alternative Army Aircrew Eyewear.

BACKGROUND: Currently, Army aircrews needing refractive correction are issued the HGU-4/P aviator spectacles. However, a recently published survey found dissatisfaction with the current spectacle frame. The Aircrew Flight Frame (AFF) has been used by the Air Force for over 14 yr, with the AFF-OP (Operational) style used the longest. The purpose of this study was to evaluate AFF-OP performance and compatibility among U.S. Army aircrew under operational conditions. METHODS: At 1-, 6-, and 12-wk intervals, 73 Army aircrew members wore the AFF-OP eyewear and completed a Likert scale survey. There were 14 outcome measures surveyed, with the main outcome measure being frame preference. RESULTS: The AFF-OP was preferred significantly more than the HGU-4/P spectacle. Overall, 94% of aircrew responses preferred the AFF-OP and the three highest subjective reasons for AFF-OP preference were: 1) comfort around the ears without helmet or headset; 2) comfort around the ears with helmet or headset; and 3) the effect on ear cup seal. There were no statistically significant differences in responses over the three surveyed time intervals. DISCUSSION: Army aviation aircrew preferred the AFF-OP over the current HGU-4/P spectacles. Two of the top three highest subjective reasons for AFF-OP preference coincided with two of the top three operational eyewear problems reported in the recently published survey. If Army aircrew do not wear their issued eyewear, they may purchase their own frame "out of pocket." However, this can lead to use of a frame that has not been tested for compatibility and may compromise performance of aircrew life support equipment.

Effects of repetitive low-level blast exposure on visual system and ocular structures.

UNLABELLED: The purpose of this study was to determine whether repetitive exposure to low-level blasts during military breacher training produces acute and cumulative damage to the ocular tissues or visual system. The effects of low-level blast exposure on high-contrast visual acuity, contrast sensitivity, oculomotor function, color vision, visual field (VF), pupillary light reflex, corneal endothelial cell density (ECD), macular thickness, retinal nerve fiber layer thickness, and cup-to-disc ratio were assessed using a battery of standard clinical ophthalmic tests administered 10 times over a 2-year period. Data from nine breacher instructors (Cadre) were compared with data from four breacher engineers (CONTROL). The Cadre group showed higher vertical deviation at near than the CONTROL group over time. The VF mean deviation on the left eye that tended to be worse in the Cadre group was worse throughout the study, suggesting a decrease in VF sensitivity (Cadre: -0.20 +/- 0.15 dB; CONTROL: 1.05 +/- 0.15 dB; p = 0.03). The Cadre group had a reduced ECD (right eye: Cadre 2,502 cells/mm(2) vs CONTROL 2,808 cells/mm(2), p = 0.05; left eye: Cadre 2,558 cells/mm(2) vs CONTROL 2,892 cells/mm(2), p = 0.04). These results suggest that even low-level primary blast has the potential to produce occult eye injury.

Visual field dysfunctions in warfighters during different stages following blast and nonblast mTBI.

OBJECTIVES: Traumatic brain injury (TBI) is the leading injury coming out of the past decades' two major military conflicts, with mild TBI (mTBI) being the most commonly diagnosed form. The aim of this study was to assess the frequency and types of visual field (VF) defects seen at different testing stages following nonblast and blast-induced mTBI. METHODS: A comprehensive retrospective review was performed on 500 electronic health records for military personnel sustaining an mTBI during deployment, of which 166 patients were tested with both confrontation VF and 30-2 Humphrey Matrix Frequency Doubling Technology (FDT) perimetry. RESULTS: Scatter defects (48%) were the most predominantly found deficits in both blast and nonblast mTBI injury mechanisms and over postinjury test time frames. Confrontation VF was shown to be a poor qualitative predictor of VF defect. A profound decrease in VF sensitivity was noted in comparison to previously reported FDT normative data. Finally, a significant trend of decreasing VF defects was seen over time, indicating the potential usage of FDT as a visual biomarker for monitoring mTBI recovery. CONCLUSIONS: The findings of this study highlight the importance of performing threshold perimeter testing in those who have suffered an mTBI or concussion-like event.

Adaptation to a simulated central scotoma during visual search training.

Patients with a central scotoma usually use a preferred retinal locus (PRL) consistently in daily activities. The selection process and time course of the PRL development are not well understood. We used a gaze-contingent display to simulate an isotropic central scotoma in normal subjects while they were practicing a difficult visual search task. As compared to foveal search, initial exposure to the simulated scotoma resulted in prolonged search reaction time, many more fixations and unorganized eye movements during search. By the end of a 1782-trial training with the simulated scotoma, the search performance improved to within 25% of normal foveal search. Accompanying the performance improvement, there were also fewer fixations, fewer repeated fixations in the same area of the search stimulus and a clear tendency of using one area near the border of the scotoma to identify the search target. The results were discussed in relation to natural development of PRL in central scotoma patients and potential visual training protocols to facilitate PRL development.