Preethi Thiagarajan

Vergence dysfunction in mild traumatic brain injury (mTBI): a review.

Citation information: Thiagarajan P, Ciuffreda KJ & Ludlam DP. Vergence dysfunction in mild traumatic brain injury (mTBI): a review. Ophthalmic Physiol Opt 2011, 31, 456–468. doi: 10.1111/j.1475‐1313.2011.00831.x

Accommodation in mild traumatic brain injury

Accommodative dysfunction in individuals with mild traumatic brain injury (mTBI) can have a negative impact on quality of life, functional abilities, and rehabilitative progress. In this study, we used a range of dynamic and static objective laboratory and clinical measurements of accommodation to assess 12 adult patients (ages 18-40 years) with mTBI. The results were compared with either 10 control subjects with no visual impairment or normative literature values where available. Regarding the dynamic parameters, responses in those with mTBI were slowed and exhibited fatigue effects. With respect to static parameters, reduced accommodative amplitude and abnormal accommodative interactions were found in those with mTBI. These results provide further evidence for the substantial impact of mTBI on accommodative function. These findings suggest that a range of accommodative tests should be included in the comprehensive vision examination of individuals with mTBI.

Oculomotor neurorehabilitation for reading in mild traumatic brain injury (mTBI): An integrative approach

BACKGROUNDnConsidering the extensive neural network of the oculomotor subsystems, traumatic brain injury (TBI) could affect oculomotor control and related reading dysfunction.nnnOBJECTIVEnTo evaluate comprehensively the effect of oculomotor-based vision rehabilitation (OBVR) in individuals with mTBI.nnnMETHODSnTwelve subjects with mTBI participated in a cross-over, interventional study involving oculomotor training (OMT) and sham training (ST). Each training was performed for 6 weeks, 2 sessions a week. During each training session, all three oculomotor subsystems (vergence/accommodation/version) were trained in a randomized order across sessions. All laboratory and clinical parameters were determined before and after OMT and ST. In addition, nearvision-related symptoms using the Convergence Insufficiency Symptom Survey (CISS) scale and subjective visual attention using the Visual Search and Attention Test (VSAT) were assessed.nnnRESULTSnFollowing the OMT, over 80% of the abnormal parameters significantly improved. Reading rate, along with the amplitudes of vergence and accommodation, improved markedly. Saccadic eye movements demonstrated enhanced rhythmicity and accuracy. The improved reading-related oculomotor behavior was reflected in reduced symptoms and increased visual attention. None of the parameters changed with ST.nnnCONCLUSIONSnOBVR had a strong positive effect on oculomotor control, reading rate, and overall reading ability. This oculomotor learning effect suggests considerable residual neuroplasticity following mTBI.

Effect of Oculomotor Rehabilitation on Vergence Responsivity in Mild Traumatic Brain Injury

A range of dynamic and static vergence responses were evaluated in 12 individuals with mild traumatic brain injury (age: 29 +/- 3 yr) having near vision symptoms. All measures were performed in a crossover design before and after oculomotor training (OMT) and placebo (P) training. Following OMT, peak velocity for both convergence and divergence increased significantly. Increased peak velocity was significantly correlated with increased clinically based vergence prism flipper rate. Steady-state response variability for convergence reduced significantly following OMT. The maximum amplitude of convergence, relative fusional amplitudes, and near stereoacuity improved significantly. In addition, symptoms reduced significantly, and visual attention improved markedly. None of the measures were found to change significantly following P training. The significant improvement in most aspects of vergence eye movements following OMT demonstrates considerable residual brain plasticity via oculomotor learning. The improved vergence affected positively on nearwork-related symptoms and visual attention.

Versional eye tracking in mild traumatic brain injury (mTBI): Effects of oculomotor training (OMT)

Abstract Objective: To evaluate a range of objective measures of versional eye movements before and after oculomotor training (OMT) in individuals with mTBI. The results were compared with placebo (P) training. Methods: Twelve individuals with mTBI (mean ageu2009=u200929u2009±u20093 years) having oculomotor-based near-vision symptoms participated in the study. Versional eye movements were recorded objectively before and after OMT (fixation, predictable saccades, simulated reading) and P training (6 weeks each, two sessions/week, 45 minutes/session). Results: Following OMT, there was a significant (pu2009<u20090.05) reduction in the horizontal fixational error. Saccadic gain increased both horizontally and vertically (pu2009<u20090.05). The saccade ratio for the simulated reading, multiple-line paradigm reduced significantly (pu2009<u20090.05). None of the measures changed significantly following the P training. Conclusions: The versional-based OMT had a significant, positive effect on most aspects of versional tracking. These findings are suggestive of improved rhythmicity, accuracy and sequencing of saccades following OMT in mTBI as a result of oculomotor learning.

Vergence in mild traumatic brain injury: A pilot study

Vergence dysfunction in individuals with mild traumatic brain injury (mTBI) may have a negative effect on quality of life, functional abilities, and rehabilitative progress. In this study, we used a range of dynamic and static objective and subjective measures of vergence to assess 21 adult patients with mTBI and nearwork symptoms. The results were compared with 10 control adult subjects. With respect to dynamic parameters, responses in those with mTBI were slowed, variable, and delayed. With respect to static parameters, reduced near point of convergence and restricted near vergence ranges were found in those with mTBI. The present results provide evidence for the substantial adverse effect of mTBI on vergence function.

Effect of Oculomotor Rehabilitation on Accommodative Responsivity in Mild Traumatic Brain Injury

Accommodative dysfunction is a common oculomotor sequelae of mild traumatic brain injury (mTBI). This study evaluated a range of dynamic (objective) and static (subjective) measures of accommodation in 12 nonstrabismic individuals with mTBI and near vision-related symptoms before and after oculomotor training (OMT) and placebo (P) training (6 wk, two sessions per week, 3 h of training each). Following OMT, the dynamics of accommodation improved markedly. Clinically, there was a significant increase in the maximum accommodative amplitude both monocularly and binocularly. In addition, the near vision symptoms reduced along with improved visual attention. None of the measures were found to change significantly following P training. These results provide evidence for a significant positive effect of the accommodatively based OMT on accommodative responsivity. Such improvement is suggestive of oculomotor learning, demonstrating considerable residual brain-visual system plasticity in the adult compromised brain.

Proposed Objective Visual System Biomarkers for Mild Traumatic Brain Injury

The challenge and search for objectively based biomarkers to assess for the presence of concussion/mild traumatic brain injury is a high priority for the military establishment. We present a documented overview of specific test areas and related targeted, high-yield, objectively based parameters that may be potential vision biomarkers for the detection of concussion/mild traumatic brain injury based on results from our laboratory and others, with emphasis on oculomotor aspects. These findings have military relevance with respect to the initial diagnosis in the battlefield and in the far-forward medical facilities, pre-/postdeployment issues, pre-/postvisual rehabilitation evaluation, fitness-for-duty assessment, and establishment of a return-to-duty timeline.

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 (nu2009=u20097) 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 (8–13u2009Hz) 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.

Pupillary responses to light in chronic non-blast-induced mTBI.

Abstract Purpose: To evaluate objectively and quantitatively human pupillary responses to a light stimulus under photopic conditions in individuals with non-blast-induced, chronic, mild traumatic brain injury (mTBI). Methods: Seventeen individuals with chronic, non-blast-induced mTBI and 15 visually-normal (VN) controls were tested (aged 21–45 years). Pupillary responsivity to a brief step-input light stimulus was assessed objectively in each eye for 5 seconds using the Neuroptics PLR-200 monocular, hand-held pupillometer with its pre-set and automated eight parameter analysis. Results: Five of the eight parameters assessed were significantly reduced (pu2009≤u20090.05) in the mTBI group as compared to the VN control group: maximum (or peak) constriction velocity, average constriction velocity, average dilation velocity, maximum diameter and amplitude of constriction. The remaining three parameters were similar in each group (pu2009>u20090.05): constriction latency, 75% dilation recovery time and minimum diameter. Conclusions: The slowed dilation dynamics and reduced maximum pupillary diameter in mTBI suggest deficiency primarily of the sympathetic control system. The reduced peak velocities and related amplitudes suggest subtle parasympathetic involvement.