Concurrent vision dysfunctions in convergence insufficiency with traumatic brain injury

Visual system pathology in humans and animal models of blast injury

Injury from blast exposure is becoming a more prevalent cause of death and disability worldwide. The devastating neurological impairments that result from blasts are significant and lifelong. Progress in the development of effective therapies to treat injury has been slowed by its heterogeneous pathology and the dearth of information regarding the cellular mechanisms involved. Within the last decade, a number of studies have documented visual dysfunction following injury. This brief review examines damage to the visual system in both humans and animal models of blast injury. The in vivo use of the retina as a surrogate to evaluate brain injury following exposure to blast is also highlighted.

Adaptation to Progressive Additive Lenses: Potential Factors to Consider

People develop presbyopia as part of the normal aging process. Most presbyopes adapt to progressive additive lens (PALs), while others do not. This investigation sought to determine whether the ability to modify disparity vergence or phoria was correlated to PALs adaptation. In experiment 1, a double-step paradigm quantified the ability to modify convergence responses in sixteen presbyopes. In experiment 2, thirty-one incipient presbyopes participated in a 5-minute sustained fixation task to evoke phoria adaptation where the magnitude and rate of phoria adaptation were measured. Then, the experiment was repeated after wearing PALs for one month. Linear regression analyses were conducted between the following parameters: near point of convergence, positive fusional vergence at near, vergence facility, net change in the magnitude of phoria adaptation, and the rate of phoria adaptation. The ability to change convergence average peak velocity was significantly greater (p < 0.03) in presbyopic PALs adapters compared to presbyopic PALs non-adapters. The rate of phoria adaptation and vergence facility were significantly greater (p < 0.03) in incipient presbyopic PALs adapters compared to incipient presbyopic PALs non-adapters. Vergence facility and the rate of phoria adaptation may have potential clinical utility in differentiating which patients may adapt to PALs and which ones will have more difficulty.

A Practical Concussion Physical Examination Toolbox

CONTEXT

With heightened awareness of concussion, there is a need to assess and manage the concussed patient in a consistent manner. Unfortunately, concussion physical examination has not been standardized or supported by evidence. Important questions remain about the physical examination.

EVIDENCE ACQUISITION

Review of ClinicalKey, Cochrane, MEDLINE, and PubMed prior to July 2015 was performed using search terms, including concussion, mTBI, physical examination, mental status, cranial nerves, reflexes, cervical, vestibular, and oculomotor. The references of the pertinent articles were reviewed for other relevant sources.

STUDY DESIGN

Clinical review.

LEVEL OF EVIDENCE

Level 3.

RESULTS

The pertinent physical examination elements for concussion include evaluation of cranial nerves, manual muscle testing, and deep tendon reflexes; inspecting the head and neck for trauma or tenderness and cervical range of motion; Spurling maneuver; a static or dynamic balance assessment; screening ocular examination; and a mental status examination that includes orientation, immediate and delayed recall, concentration, mood, affect, insight, and judgment. Other examination elements to consider, based on signs, symptoms, or clinical suspicion, include testing of upper motor neurons, cervical strength and proprioception, coordination, pupillary reactivity, and visual acuity; examination of the jaw, temporomandibular joint, and thoracic spine; fundoscopic evaluation; orthostatic vital signs; assessment of dynamic visual acuity; and screening for depression, anxiety, substance abuse disorders, and preinjury psychiatric difficulties.

CONCLUSION

Various elements of the physical examination, such as screening ocular examination, cervical musculoskeletal examination, static and/or dynamic balance assessment, and mental status examination, appear to have utility for evaluating concussion; however, data on validity are lacking.

A Positive Vestibular/Ocular Motor Screening (VOMS) Is Associated With Increased Recovery Time After Sports-Related Concussion in Youth and Adolescent Athletes

BACKGROUND

Vestibular and ocular motor impairments are routinely reported in patients with sports-related concussion (SRC) and may result in delayed return to play (RTP). The Vestibular/Ocular Motor Screening (VOMS) assessment has been shown to be consistent and sensitive in identifying concussion when used as part of a comprehensive examination. To what extent these impairments or symptoms are associated with length of recovery is unknown.

PURPOSE

To examine whether symptom provocation or clinical abnormality in specific domains of the VOMS results in protracted recovery (time from SRC to commencement of RTP protocol).

STUDY DESIGN

Cohort study (prognosis); Level of evidence, 2.

METHODS

A retrospective chart review was conducted of 167 patients (69 girls, 98 boys; mean ± SD age, 15 ± 2 years [range, 11-19 years]) presenting with SRC in 2014. During the initial visit, VOMS was performed in which symptom provocation or clinical abnormality (eg, unsmooth eye movements) was documented by use of a dichotomous scale (0 = not present, 1 = present). The VOMS used in this clinic consisted of smooth pursuits (SMO_PUR), horizontal and vertical saccades (HOR_SAC and VER_SAC), horizontal and vertical vestibular ocular reflex (HOR_VOR and VER_VOR), near point of convergence (NPC), and accommodation (ACCOM). Domains were also categorized into ocular motor (SMO_PUR, HOR_SAC, VER_SAC, NPC, ACCOM) and vestibular (HOR_VOR, VER_VOR). Cox proportional hazard models were used to explore the relationship between the domains and recovery. Alpha was set at P ≤ .05.

RESULTS

Symptom provocation and/or clinical abnormality in all domains except NPC ( P = .107) and ACCOM ( P = .234) delayed recovery (domain, hazard ratio [95% CI]: SMO_PUR, 0.65 [0.47-0.90], P = .009; HOR_SAC, 0.68 [0.50-0.94], P = .018; VER_SAC, 0.55 [0.40-0.75], P < .001; HOR_VOR, 0.68 [0.49-0.94], P = .018; VER_VOR, 0.60 [0.44-0.83], P = .002). The lowest crude hazard ratio was for ocular motor category (0.45 [0.32-0.63], P < .001).

CONCLUSION

These data suggest that symptom provocation/clinical abnormality associated with all domains except NPC and ACCOM can delay recovery after SRC in youth and adolescents. Thus, the VOMS not only may augment current diagnostic tools but also may serve as a predictor of recovery time in patients with SRC. The findings of this study may lead to more effective prognosis of concussion in youth and adolescents.

Adaptive reorganization of retinogeniculate axon terminals in dorsal lateral geniculate nucleus following experimental mild traumatic brain injury

The pathologic process in traumatic brain injury marked by delayed axonal loss, known as diffuse axonal injury (DAI), leads to partial deafferentation of neurons downstream of injured axons. This process is linked to persistent visual dysfunction following mild traumatic brain injury (mTBI), however, examination of deafferentation in humans is impossible with current technology. To investigate potential reorganization in the visual system following mTBI, we utilized the central fluid percussion injury (cFPI) mouse model of mTBI. We report that in the optic nerve of adult male C57BL/6J mice, axonal projections of retinal ganglion cells (RGCs) to their downstream thalamic target, dorsal lateral geniculate nucleus (dLGN), undergo DAI followed by scattered, widespread axon terminals loss within the dLGN at 4days post-injury. However, at 10days post-injury, significant reorganization of RGC axon terminals was found, suggestive of an adaptive neuroplastic response. While these changes persisted at 20days post-injury, the RGC axon terminal distribution did not recovery fully to sham-injury levels. Our studies also revealed that following DAI, the segregation of axon terminals from ipsilateral and contralateral eye projections remained consistent with normal adult mouse distribution. Lastly, our examination of the shell and core of dLGN suggested that different RGC subpopulations may vary in their susceptibility to injury or in their contribution to reorganization following injury. Collectively, these findings support the premise that subcortical axon terminal reorganization may contribute to recovery following mTBI, and that different neural phenotypes may vary in their contribution to this reorganization despite exposure to the same injury.

Anoxic Brain Injury Secondary to Metabolic Encephalopathy

PURPOSE

To discuss the clinical case of a patient suffering visual dysfunction secondary to a metabolic brain injury, the patient's visual rehabilitative treatment, and outcomes.

CASE REPORT

A 24-year-old Caucasian male presented to the Southern Arizona Veteran's Affairs Healthcare System's Traumatic Brain Injury (TBI) eye clinic for evaluation and treatment of visual dysfunction secondary to an anoxic brain injury suffered 4 months before. Symptoms included persistent right homonymous hemianopia, oculomotor dysfunction, and a visual information processing deficit. After 5 weeks of vision rehabilitation, the patient was reassessed and displayed significant improvement in both signs and symptoms.

CONCLUSIONS

The syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is a metabolic syndrome that causes hyponatremia and, in severe cases, encephalopathy and anoxic brain injury. Damage to the visual pathways can produce visual field, ocular motility, and binocular vision deficits. Comprehensive treatment including rehabilitative vision therapy bolstering the natural neuroplasticity process can provide improvements in patients' quality of life.

Near Point of Convergence After a Sport-Related Concussion: Measurement Reliability and Relationship to Neurocognitive Impairment and Symptoms

BACKGROUND

Convergence insufficiency (CI) is a common binocular vision deficit after a sport-related concussion (SRC). CI may result in visual discomfort and vision-mediated functional difficulties such as slowed reading and compromised attention, leading to impaired academic, work, and sport performance.

PURPOSE

To test the reliability of repeated near point of convergence (NPC) measurements in a sample of athletes after an SRC; compare the symptoms and cognitive impairment of athletes with normal NPC to those with CI after an SRC; and explore the relationship among age, sex, learning disability, migraine history, and CI.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

A total of 78 athletes (mean age, 14.31 ± 2.77 years) who were seen a mean 5.79 ± 5.63 days after an SRC were administered 3 trials of an NPC assessment, along with neurocognitive (Immediate Post-Concussion Assessment and Cognitive Testing [ImPACT]) and symptom assessments. Patients were divided into normal NPC (NPC ≤ 5 cm; n = 45) and CI (NPC >5 cm; n = 33) groups. Intraclass correlation coefficients (ICCs) and repeated-measures analyses of variance (ANOVAs) assessed the consistency of NPC across the 3 trials. The ANOVAs were employed to examine differences on neurocognitive composites and symptoms between the normal NPC and CI groups. Stepwise regressions (controlling for age and symptom scores on the Post-Concussion Symptom Scale [PCSS]) were conducted to evaluate the predictive utility of the NPC distance for neurocognitive impairment.

RESULTS

Groups did not differ on demographic or injury characteristics. NPC differed between trial 1 and trials 2 (P = .02) and 3 (P = .01) for the CI group but not the normal NPC group. Internal consistency was high across NPC measurements (ICC range, 0.95-0.98). Patients with CI performed worse on verbal memory (P = .02), visual motor speed (P = .02), and reaction time (P = .001, η(2) = .13) and had greater total symptom scores (P = .02) after the injury. Results of hierarchical regression revealed that the NPC distance contributed significantly to the model for reaction time (P < .001).

CONCLUSION

CI was common (~42%) in athletes evaluated within 1 month after an SRC. Athletes with CI had worse neurocognitive impairment and higher symptom scores than did those with normal NPC. Clinicians should consider routinely screening for NPC as part of a comprehensive concussion evaluation to help inform treatment recommendations, academic accommodations, and referrals for vision therapy.

Automated Perimetry and Visual Dysfunction in Blast-Related Traumatic Brain Injury

PURPOSE

To evaluate feasibility and results of automated perimetry in veterans with combat blast neurotrauma.

DESIGN

Prospective, longitudinal, observational case series.

PARTICIPANTS

Sixty-one patients in a Veterans Affairs Polytrauma Center diagnosed with traumatic brain injury (TBI) from combat blast exposure.

METHODS

Study participants underwent automated perimetry at baseline (median interval, 2 months after injury) (Humphrey Field Analyzer, Carl Zeiss Meditec, Dublin, CA, Swedish Interactive Threshold Algorithm 30-2 Standard or Fast), and 36 of them were followed up (median interval, 10 months after baseline). Presence of significant mean deviation and pattern standard deviation was determined for testing with reliability indices ≤20% for fixation loss, 15% for false-positives, and 33% for false-negatives. Test-retest stability of global visual field indices was assessed for tests with these cutoffs or with elevated fixation loss. Associations between global visual field defects and predictors were examined.

MAIN OUTCOME MEASURES

Global visual field indices (mean deviation and pattern standard deviation).

RESULTS

Among 61 study participants (109 study eyes) with baseline testing, a field that met reliability cutoffs was obtained for 48 participants (79%) and 78 eyes (72%). Fixation loss was found in 29% of eyes in initial testing. Nine study participants (15%) demonstrated hemianopia or quadrantanopia, and an additional 36% had an abnormal global visual field index. Global indices were relatively stable at follow-up testing for tests meeting fixation-loss cutoffs and tests that did not. Visual scotomas due to post-chiasmal lesions were associated with moderate to severe TBI or penetrating head injury, but other visual field deficits were prevalent across the range of mild to severe TBI. Ocular injury to the retina or choroid, poorer visual acuity, and pupillary defect were associated with visual field defects. Participants with depressed visual field sensitivity reported lower visual quality of life.

CONCLUSIONS

Reliable automated perimetry can be accomplished in most patients with TBI from combat blast exposure and reveals high rates of visual field deficits, indicating that blast forces may significantly affect the eye and visual pathways.

Spatial Neglect Hinders Success of Inpatient Rehabilitation in Individuals With Traumatic Brain Injury: A Retrospective Study

Background Current knowledge about spatial neglect and its impact on rehabilitation mostly originates from stroke studies. Objective To examine the impact of spatial neglect on rehabilitation outcome in individuals with traumatic brain injury (TBI). Methods The retrospective study included 156 consecutive patients with TBI (73 women; median age = 69.5 years; interquartile range = 50-81 years) at an inpatient rehabilitation facility (IRF). We examined whether the presence of spatial neglect affected the Functional Independence Measure (FIM) scores, length of stay, or discharge disposition. Based on the available medical records, we also explored whether spatial neglect was associated with tactile sensation or muscle strength asymmetry in the extremities and whether specific brain injuries or lesions predicted spatial neglect. Results In all, 30.1% (47 of 156) of the sample had spatial neglect. Sex, age, severity of TBI, or time postinjury did not differ between patients with and without spatial neglect. In comparison to patients without spatial neglect, patients with the disorder stayed in IRF 5 days longer, had lower FIM scores at discharge, improved slower in both Cognitive and Motor FIM scores, and might have less likelihood of return home. In addition, left-sided neglect was associated with asymmetric strength in the lower extremities, specifically left weaker than the right. Finally, brain injury-induced mass effect predicted left-sided neglect. Conclusions Spatial neglect is common following TBI, impedes rehabilitation progress in both motor and cognitive domains, and prolongs length of stay. Future research is needed for linking specific traumatic injuries and lesioned networks to spatial neglect and related impairment.

Vestibulo-ocular dysfunction in pediatric sports-related concussion

OBJECT

The objective of this study was 2-fold: 1) to examine the prevalence of vestibulo-ocular dysfunction (VOD) among children and adolescents with acute sports-related concussion (SRC) and postconcussion syndrome (PCS) who were referred to a multidisciplinary pediatric concussion program; and 2) to determine if VOD is associated with the development of PCS in this cohort.

METHODS

The authors conducted a retrospective review of all patients with acute SRC (presenting 30 days or less postinjury) and PCS (3 or more symptoms for at least 1 month) referred to a multidisciplinary pediatric concussion program between September 2013 and July 2014. Initial assessment included clinical history, physical examination, and Post-Concussion Symptom Scale assessment. Patients were also assessed for VOD, which was defined as more than one subjective vestibular and oculomotor complaint (dizziness, blurred vision, and so on) and more than one objective physical examination finding (abnormal smooth pursuits, saccades, vestibulo-ocular reflex, and so on). This study was approved by the local institutional ethics review board.

RESULTS

A total of 101 patients (mean age 14.2 years, SD 2.3 years; 63 male and 38 female patients) participated, including 77 (76.2%) with acute SRC and 24 (23.8%) with PCS. Twenty-two of the 77 patients (28.6%) with acute SRC and 15 of the 24 (62.5%) with PCS met the clinical criteria for VOD. The median duration of symptoms was 40 days (interquartile range [IQR] 28.5-54 days) for patients with acute SRC who had VOD compared with 21 days (IQR 13-32 days) for those without VOD (p = 0.0001). There was a statistically significant increase in the adjusted odds of developing PCS among patients with acute SRC who had VOD compared with those without VOD (adjusted OR 4.10; 95% CI 1.04-16.16).

CONCLUSIONS

Evidence of VOD was detected in a significant proportion of children and adolescents with acute SRC and PCS who were referred to a multidisciplinary pediatric concussion program. This clinical feature was a significant risk factor for the subsequent development of PCS in this pediatric acute SRC cohort.

Sensitivity and specificity of an eye movement tracking-based biomarker for concussion

Object:

The purpose of the current study is to determine the sensitivity and specificity of an eye tracking method as a classifier for identifying concussion.

Methods:

Brain injured and control subjects prospectively underwent both eye tracking and Sport Concussion Assessment Tool 3. The results of eye tracking biomarker based classifier models were then validated against a dataset of individuals not used in building a model. The area under the curve (AUC) of receiver operating characteristics was examined.

Results:

An optimal classifier based on best subset had an AUC of 0.878, and a cross-validated AUC of 0.852 in CT- subjects and an AUC of 0.831 in a validation dataset. The optimal misclassification rate in an external dataset (n = 254) was 13%.

Conclusion:

If one defines concussion based on history, examination, radiographic and Sport Concussion Assessment Tool 3 criteria, it is possible to generate an eye tracking based biomarker that enables detection of concussion with reasonably high sensitivity and specificity.

The impact of 3D and 2D TV watching on neurophysiological responses and cognitive functioning in adults

BACKGROUND

Watching three-dimensional television (3D TV) may strain the eyes. However, other potential harmful effects of 3D TV watching have been rarely investigated. The current study examined the impact of 3D TV watching on neurophysiological responses and cognitive functioning as compared with two-dimensional TV (2D TV) watching.

METHODS

A total of 72 individuals were randomly assigned to either a 3D TV watching group or a 2D TV watching group. Electroencephalography (EEG) was used to measure neurophysiological responses, and computerized neurocognitive tests were conducted immediately before and after TV watching. The Simulator Sickness Questionnaire (SSQ) was used to assess visual discomfort.

RESULTS

There was a significant change in visual discomfort between the two groups (SSQ score at baseline: 2.28 ± 3.05 for the 3D TV group and 3.69 ± 3.49 for the 2D TV group; SSQ score after watching TV: 4.6 ± 3.35 for the 3D TV group and 4.03 ± 3.47 for the 2D TV group), and this change was greater for the 3D TV watching group (P = 0.025). However, 3D TV watching did not have a differential impact on EEG responses. Furthermore, there were no significant differences between the groups in terms of changes in cognitive performance, except for a subtle difference in backward digit span performance.

CONCLUSION

Our findings suggest that 3D TV watching is as safe as 2D TV watching in terms of neurophysiological responses and cognitive functioning. Potential harmful effects of TV viewing might be similar regardless of whether 3D or 2D TV is viewed.

Consequences of traumatic brain injury for human vergence dynamics

Purpose: Traumatic brain injury involving loss of consciousness has focal effects in the human brainstem, suggesting that it may have particular consequences for eye movement control. This hypothesis was investigated by measurements of vergence eye movement parameters.

Methods: Disparity vergence eye movements were measured for a population of 123 normally sighted individuals, 26 of whom had suffered diffuse traumatic brain injury (dTBI) in the past, while the remainder served as controls. Vergence tracking responses were measured to sinusoidal disparity modulation of a random-dot field. Disparity vergence step responses were characterized in terms of their dynamic parameters separately for the convergence and divergence directions.

Results: The control group showed notable differences between convergence and divergence dynamics. The dTBI group showed significantly abnormal vergence behavior on many of the dynamic parameters.

Conclusion: The results support the hypothesis that occult injury to the oculomotor control system is a common residual outcome of dTBI.

Falls and fallers in traumatic brain injury (TBI) rehabilitation settings: an integrative review

PURPOSE

To critically appraise the research literature on the nature of falls and fallers in traumatic brain injury (TBI) rehabilitation settings.

METHOD

An integrative review of the literature using thematic analysis was undertaken. Papers identified via a systematic search strategy were independently appraised by two reviewers. A data extraction instrument was developed to record results and to aid identification of themes in the literature. Critical Appraisal Skills Programme instruments were utilised to conduct a methodological critique of the papers included.

RESULTS

Thirteen studies were identified as having between 4% and 100% TBI patients in their study cohorts. From these papers, up to 71% of falls took place in a patient's bedroom occurring in peaks and troughs over a 24-h period. With some divergent results, nine themes were identified describing faller characteristics including: (1) functional mobility impairments; (2) dizziness; (3) bladder and bowel dysfunction; (4) certain medications and number of medications prescribed; (5) executive functioning; (6) patient age; (7) fear of falling; (8) coma length following TBI; and (9) Functional Independence Measure (FIM™) total score, subscale scores and particular individual items.

CONCLUSIONS

Being a multifactorial phenomenon, falls are a complex clinical issue. Despite the heterogeneity of diagnosis related groups (DRGs) in the included studies, TBI patients were identified as a high falls risk patient population in several studies. Implications for Rehabilitation Due to multisystem impairments, falls in the traumatic brain injury (TBI) rehabilitation context are a multifactorial and significant clinical issue. When interpreting and generalising results from research into falls, clinicians need to be mindful that falls and faller characteristics may be dependent on study setting and patient population. There is need for context specific research into faller characteristics following a TBI; particularly in relation to post-traumatic amnesia.

Chronic visual dysfunction after blast-induced mild traumatic brain injury

The purpose of this study was to investigate the long-term visual dysfunction in patients after blast-induced mild traumatic brain injury (mbTBI) using a retrospective case series of 31 patients with mbTBI (>12 mo prior) without eye injuries. Time since mbTBI was 50.5 +/- 19.8 mo. Age at the time of injury was 30.0 +/- 8.3 yr. Mean corrected visual acuity was 20/20. Of the patients, 71% (n = 22) experienced loss of consciousness; 68% (n = 15) of patients in this subgroup were dismounted during the blast injury. Overall, 68% (n = 21) of patients had visual complaints. The most common complaints were photophobia (55%) and difficulty with reading (32%). Of all patients, 25% were diagnosed with convergence insufficiency and 23% had accommodative insufficiency. Patients with more than one mbTBI had a higher rate of visual complaints (87.5%). Asymptomatic patients had a significantly longer time (62.5 +/- 6.2 mo) since the mbTBI than symptomatic patients (42.0 +/- 16.4 mo, p < 0.004). Long-term visual dysfunction after mbTBI is common even years after injury despite excellent distance visual acuity and is more frequent if more than one incidence of mbTBI occurred. We recommend obtaining a careful medical history, evaluation of symptoms, and binocular vision assessment during routine eye examinations in this prepresbyopic patient population.

Clinical test responses to different orthoptic exercise regimes in typical young adults

Purpose

The relative efficiency of different eye exercise regimes is unclear, and in particular the influences of practice, placebo and the amount of effort required are rarely considered. This study measured conventional clinical measures following different regimes in typical young adults.

Methods

A total of 156 asymptomatic young adults were directed to carry out eye exercises three times daily for 2 weeks. Exercises were directed at improving blur responses (accommodation), disparity responses (convergence), both in a naturalistic relationship, convergence in excess of accommodation, accommodation in excess of convergence, and a placebo regime. They were compared to two control groups, neither of which were given exercises, but the second of which were asked to make maximum effort during the second testing.

Results

Instruction set and participant effort were more effective than many exercises. Convergence exercises independent of accommodation were the most effective treatment, followed by accommodation exercises, and both regimes resulted in changes in both vergence and accommodation test responses. Exercises targeting convergence and accommodation working together were less effective than those where they were separated. Accommodation measures were prone to large instruction/effort effects and monocular accommodation facility was subject to large practice effects.

Conclusions

Separating convergence and accommodation exercises seemed more effective than exercising both systems concurrently and suggests that stimulation of accommodation and convergence may act in an additive fashion to aid responses. Instruction/effort effects are large and should be carefully controlled if claims for the efficacy of any exercise regime are to be made.