What is Traumatic Brain Injury? (TBI)

As defined by the Brain Injury Association of America (BIAA), Traumatic Brain Injury (TBI) is defined as an alteration in brain function, or other evidence of brain pathology, caused by an external force.

Causes of a Traumatic Brain Injury (TBI) include:

  • Falls are the most common cause of traumatic brain injury overall, particularly in older adults and young children.
  • Violence/Assault Examples include gunshots, domestic violence, and child abuse.
  • Motor vehicle accidents Vehicle-related collisions involving cars, motorcycles or bicycles — and pedestrians involved in such accidents — are a frequent cause of traumatic brain injury.
  • Sports injuries Traumatic brain injuries may be caused by head trauma experienced in several sports, including soccer, boxing, football, baseball, lacrosse, skateboarding, hockey, and other high-impact sports. These are particularly common in youth.
  • Shaken Baby Syndrome is a traumatic brain injury caused in infants due to violent shaking.
  • blast injuries The concussive force of a blast is a common cause of traumatic brain injury in active-duty military personnel. Many researchers believe that the pressure wave passing through the brain significantly disrupts brain function.

Types of Traumatic Brain Injury (TBI)

Brain injuries may be classified as traumatic or non-traumatic to describe the cause of the injury. A non-traumatic brain injury is an alteration in brain function or pathology caused by an internal force. Brain injuries may also be classified as mild, moderate, or severe to indicate the initial severity of the injury. Other terms, such as diffuse or penetrating, may be used to describe the type injury.

Mild Brain Injury consists of the following attributes:

  • Brief, if any, loss of consciousness
  • Vomiting and Dizziness
  • Lethargy
  • Memory Loss

Moderate Brain Injury consists of the following attributes:

  • Unconsciousness up to 24 hours
  • Signs of brain trauma
  • Contusions or bleeding
  • Signs of injury on neuroimaging

Severe Brain Injury consists of the following attributes:

  • Unconsciousness exceeding 24 hours (coma)
  • No sleep/wake cycle during loss of consciousness (LOC)
  • Signs of injury appear on neuroimaging tests

What happens during a Brain Injury?

Immediately following a brain injury:

Brain tissue reacts to the trauma from the injury with a series of biochemical and other physiological responses. Substances that once were housed safely within these cells now flood the brain, further damaging and destroying brain cells in what is called secondary cell death.

Depending on the severity of brain injury, effects may include temporary loss of consciousness or coma, respiratory (breathing) problems, and/or damaged motor functions.

Diagnosis of Brain Injury

A person with a suspected brain injury should call 911, go to the emergency room, or contact a physician immediately.

According to the Brain Injury Association of America, after an impact or injury to the head, an individual can experience a variety of symptoms. Common symptoms of a brain injury include:

  • Spinal fluid (thin, clear liquid) coming out of the ears or nose
  • Loss of consciousness, coma, or semi-comatose state
  • Dilated (the black center of the eye is large and does not get smaller in light) or unequal size of pupils
  • Vision changes (blurred vision or seeing double, not able to tolerate bright light, loss of eye movement, blindness)
  • Dizziness, confusion, weakness, poor coordination, or balance problems
  • Difficulty breathing
  • Paralysis, or difficulty moving body parts
  • Slow pulse
  • Slow breathing rate, with an increase in blood pressure
  • Vomiting
  • Lethargy
  • Headache
  • Ringing in the ears (tinnitus), or changes in ability to hear
  • Difficulty with thinking skills (difficulty “thinking straight”, memory problems, poor judgment, poor attention span, a slowed thought processing speed)
  • Inappropriate emotional responses (irritability, easily frustrated, inappropriate crying or laughing)
  • Difficulty speaking (slurred speech, difficulty swallowing)
  • Body numbness or tingling
  • Loss of bowel control or bladder control

Diagnosing brain injury and determining injury severity are two different things. In cases where the injury is more severe, it is usually clear from the individual's symptoms that some type of brain injury has occurred. In situations where the brain injury is mild or moderate, further assessment is often needed to diagnose the brain injury.

Vision issues after a Traumatic Brain Injury:

According to the American Optometric Association, 90% of patients with traumatic brain injuries will suffer visual symptoms. Drs. Neera Kapoor and Kenneth J. Ciuffreda (SUNY College of Optometry) explain that vision disturbances following a traumatic brain injury (TBI) include Accommodative Dysfunction; Abnormal saccades, pursuits, and fixation; Nystagmus; Vergence Dysfunction such as Convergence Insufficiency, Intermittent Exotropia, and Exophoria; Visual Field Deficits; and Photosensitivity." (2)

Kapoor and Ciuffreda also outline the common vision complaints associated with these disturbances:

  • Intermittent or constant blurred vision
  • Loss of place while reading or skipping/re-reading words while reading
  • Reduced, inefficient reading speed
  • Double vision (diplopia)
  • Eyestrain
  • Motion sensitivity
  • "Shimmering vision" or the appearance of text "floating" on a page
  • Spatial perceptual deficits
  • Spatial awareness deficits
  • Extreme light sensitivity
  • Waviness of vision
  • Graininess of vision

Light and Visual Sensitivity:

Many TBI patients develop a hypersensitive visual system. Slight changes in prescription and visual environments such as lighting (fluorescent and computer screens) and patterns can become very noticeable and distracting. Also, the ability to filter out visual noise (information the brain normally perceives as irrelevant to what a person is focusing on) is impaired, sometimes making the motion of objects, people and crowded spaces overwhelming. In addition, one's ability to orient oneself in visual space is impaired, resulting in significant discomfort, disorientation, dizziness, and confusion. (3)

Eye Teaming:

Eye teaming is a term that describes convergence (crossing the eyes together to aim at a near object) and divergence (relaxing the eyes to aim at a more distant object). If eye teaming ability is affected, this could result in double vision (diplopia) or reduced depth perception. Eye-teaming disorders due to TBI include convergence insufficiency, intermittent exotropia, exophoria, and vertical heterophorias. In addition to double vision (which may be intermittent or constant), patients may also experience eyestrain, a sense that text is floating on the page, and visual sensitivity to motion in their daily life and environment. (2)(3)

This is a great animated representation, provided on the Neuro Optometric Rehabilitation Association website, of an eye teaming disorder:

Eye Tracking:

Eye-tracking describes one's ability to fixate (locking on to an object and following it) and saccade (changing fixation from one object to another). This is an often unnoticed but crucial skill needed for reading since it requires that a person track words across sentences and then re-fixate from the end of one sentence to the next. Patients with TBIs can experience nystagmus, a condition where one or both eyes drift off the target and then correct it to re-fixate resulting in a continuous movement of the eye during fixation. Patients may experience losing their place while reading, having to re-read words or sentences, reduced and less efficient reading speeds, and disrupted visual scanning patterns as part of their everyday activities. (2)(3)

This is a great animated representation, provided on the Neuro Optometric Rehabilitation Association website, of an eye tracking disorder:

Eye Focusing:

The ability to focus the eye is described as an accommodative facility (the ease of switching eye focusing between different distances) and accommodative amplitude (the maximum amount of focusing the eyes can do). Damaged eye focusing skills can result in blurry vision that is either constant or intermittent. Patients may experience difficulty when shifting from far to near (accommodative infacility), or from near to far (accommodative excess or accommodative infacility), or just initially when at near (accommodative insufficiency) or for a longer duration at near (ill-sustained accommodation). (2)(3)

This is a great animated representation, provided on the Neuro Optometric Rehabilitation Association website, of an eye focusing problem:

Neuro Optometric Rehabilitation for TBI

As mentioned on the Neuro Optometric Rehabilitation Association website, visual problems are often overlooked during initial treatment of a brain injury and in some cases; symptoms may not be present until sometime following the injury. If you notice any changes in your vision following a concussion or some other head trauma, don’t ignore them: Immediately contact your eye care professional. It is important to determine the cause of the vision change. Early diagnosis leads to appropriate treatment and/or referral to a specialist, such as a Neuro-Optometric Rehabilitation Optometrist.

Left untreated, visual system disorders can have serious consequences, such as the ability to organize and make sense of visual information along with poor depth perception and difficulties concerning balance and posture.



*Neuro-Optometric Rehabilitation Association (NORA) website

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