Studies: Acquired Brain Injury

Chronic Visual Dysfunction After Blast-Induced Mild Traumatic Brain Injury

Published in 2014 in the Journal of Rehabilitation Research and Development, this research article outlines the long-term visual dysfunction in veterans who have suffered blast induced mild traumatic brain injury (mTBI). It was once thought that symptoms of mTBI resolve over the period of six to twelve months. This research, and several others, shows that the visual effects of mTBI last far beyond six to twelve months. Every subject had suffered a traumatic brain injury more than one year prior to the study (average was more than 4 years prior). Here is what they found:

 

Every patient had a best-corrected visual acuity of 20/20

 

Despite clear vision, 68% reported visual complaints

  • 55% reported photophobia (sensitivity to light)

  • 32% reported reading difficulties

  • 25% reported convergence insufficiency (an eye teaming disorder)

  • 23% reported accommodative insufficiency (an eye focusing disorder)

  • 13% reported diplopia (double vision)

 

The Department of Defense reports over 250,000 servicemembers have been diagnosed with a traumatic brain injury since the conflicts in Afghanistan and Iraq began. In the past five years the reported number of cases is 542 per month. The high incidence of these vision conditions in the mTBI population led the researchers to conclude “long-term visual dysfunction after mTBI is common even years after injury despite excellent visual acuity.” The researchers also recommended a binocular vision assessment be performed in this patient population. Proper diagnosis and treatment of these visual conditions is important to the patient's quality of life, for both improvement of symptoms and employment (75% of unemployed veterans were diagnosed with convergence insufficiency or accommodative insufficiency as compared to 33% of the employed veterans in this study). 

 

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Vergence In Mild Traumatic Brain Injury: A Pilot Study

Vergence dysfunction with mild traumatic brain injury (mTBI) may have negative effect on quality of life, functional abilities, and the rehabilitative process. Published in 2012, this study assesses a wide range of both static and dynamic vergence (eye teaming and tracking) abilities in patients with mild traumatic brain injury (mTBI) as compared to control (non-TBI) subjects. The results of this study confirm the findings from previous studies that showed vergence abilities are negatively impacted by mTBI. It also identified several dynamic aspects of vergence (not previously studied) that are reduced in patients with mTBI.

 

The study revealed significant differences for a range of dynamic vergence functions between the mTBI and control (non-TBI) groups.

  • All subjects in the mTBI group demonstrated decreased peak vergence velocity and increased latency for both convergence and divergence.
    This suggests abnormally slowed sensory processing and motor response due to a neurological control signal problem.

  • Vergence facility (flexibility) was significantly lower in the mTBI group.

The researchers demonstrated several static vergence measures that are reduced in the mTBI group.

  • Significantly receded near point of convergence (indicating convergence insufficiency)

  • Significantly reduced convergence ranges (indicating convergence insufficiency)

  • Reduced steroepsis (3D vision)

These reduced vergence abilities are likely to have a negative impact on vision-related activities, including: reading, visual scanning, tracking in depth, and performance in the work place (especially computer-related activities). These abilities can also lead to inadequate progress in other rehabilitative services. The researchers concluded that “the need exists to recognize and diagnose these vergence dysfunctions. Early visual intervention (spectacles, prism, vision therapy) can be implemented.” 

 

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Oculomotor Rehabilitation For Reading in Acquired Brain Injury

 

An article published in Neuro Rehabilitation discusses a research project aimed to assess reading-related oculomotor rehabilitation in individuals with acquired brain injury; either stroke or traumatic brain injury. 65% of patients with either traumatic brain injury or stroke manifest oculomotor dysfunction. The abnormal eye movements can have a negative impact on a number of visual tasks, including reading. One of the most common goals of our acquired brain injury patients at Advanced Vision Therapy Center is to regain reading abilities lost due to an acquired brain injury. Fortunately, the eye movements and visual processes needed to be an effective reader can be trained.

 

Reading requires precise, rhythmic, and automatically-executed sequences of saccadic eye movements divided by brief fixational pauses. The researchers trained oculomotor function, specifically fixation, pursuits and saccades, that are used during reading. The effects of the vision training program were assessed in the following ways:

 

Objectively, using infrared eye movement recording technology for simulated and actual reading.

This is the same system used at Advanced Vision Therapy Center for all of our Binocular Vision Assessments, Neuro-Optometric Assessments, and Athlete Vision Assessments.

 

Subjectively, using a reading rating-scale questionnaire.

All reported improved reading ability that was confirmed with objective oculomotor measures.

  • Length of time of reading comfort

  • Understanding of reading material

  • Attentional focus during reading

  • Reading strategy

The researches reported the following findings:

  • All individuals perceived significant increases in their overall reading ability, with the attentional-related aspects apparently spreading to other vocational and avocational task domains, such as casual conversations.”

  • There were marked objective improvements in saccadic tracking ability during the simulated reading.”

  • There were improvements in many of the reading eye movement parameters for the level ten (highest level of test) paragraphs, in particular for the stroke sub-group.”

The results of this study are consistent with previous studies in the area of reading in the post-stroke population. Research consistently shows that eye movements negatively impact reading abilities following an acquired brain injury and that these oculomotor deficits respond extremely well to vision therapy.

 

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Improvement Starts Here

With over 25 years of proven success, you can trust Advanced Vision Therapy Center to provide the care you need.

Our Clinical Director is Idaho's only residency trained optometrist in vision therapy and neuro-optometry and is a Fellow of the American Academy of Optometry.  His residency at University of California, Berkeley means he has the expertise and experience to treat even the most complex cases.

Read what our patients have to say.

Blog
Traumatic Brain Injury (TBI) is a term used within the medical community to describe an injury to the brain which is not hereditary, congenital or degenerative. Traumatic Brain Injury can be result from a blow to the head, whiplash, seizure disorders, tumors, stroke, toxic exposure, or infectious diseases to name a few. The incidence of prevalence of brain injury outnumbers breast cancer, spinal cord injury, multiple sclerosis and HIV/AIDs combined.   ... Read More
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  Convergence Insufficiency (CI) is a common eye-teaming problem which occurs when the eyes are unable to maintain the ocular posture necessary for reading or near tasks. Convergence Insufficiency results from misalignment of the eyes when focusing on up close, such as when reading. The eyes have a strong tendency to drift outward when reading or doing close up work. The exact cause is unknown.    ... Read More
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  Eye tracking, also referred to as visual tracking, is the ability of one's eyes to ?track? from left to right in an efficient manner, and ?follow? the movement of objects. Eye movements should be smooth and consistent, with the ability to be completed quickly.    ... Read More
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  The human brain measures time continuously, and has developed three general classes of timing systems: circadian, interval, and millisecond timing. Neuroscientists believe that we have distinct neural systems for processing these different types of time. Poor timing or synchronization between the three major brain networks has been implicated in several conditions.   ... Read More
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