What is traumatic brain injury?
Traumatic brain injury (TBI) is defined as any damage or alteration to brain function due to external physical force. TBIs can be caused by falls, motor vehicle accidents, assaults, concussions, gun shots, or explosions and blasts etc. There are three levels of TBI: mild, moderate and severe. About 80-90% of TBIs fall in the mild category, which is most responsive to vision therapy and rehabilitation.
Vision is the most important source of sensory information. Often, vision problems resulting from Traumatic Brain Injury are overlooked during the initial phase of testing and treatment. Frequently, these problems are hidden and neglected. Because of the close relationship between vision and the brain, TBI’s can disrupt visual processing, interrupting the flow of information to and from the brain.
Over 50% of brain pathways relate to visual function, which explains why many patients with TBI may experience one or more of the following vision problems.
- Light and Visual Sensitivity: Many brain injured patients develop a hypersensitive and fragile visual system. Slight changes in prescription and visual environment such as lighting (fluorescent and computer screens) and patterns can very noticeable. Also, the visual system’s ability to filter out visual noise is impaired, making motion and crowded spaces overwhelming. In addition, one’s ability to organize oneself in visual space is impaired, resulting in overwhelming sense of discomfort, vertigo and/or imbalance.
- Visual Hallucination: Visual hallucinations may occur as stars, flashes and spots. The formed images may represent misunderstanding of information in the brain or background “noise” from the disruption of brain tissue that is needed to process the information.
- Eye Teaming: This describes how the eyes coordinate to convergence (crossing the eyes together to aim at a near object) and divergence (relaxing the eyes to aim at a more distant object). An unstable and weak eye-teaming system may result in double vision or reduced depth perception which would affect mobility and orientation in space and watching 3D movies.
- Eye Tracking: The eye’s ability to fixate (locking on to an object and follow it) and make saccades (changing fixation from one object to another) is important for many activities of daily living. For example, when reading, we need to track words across sentences and then re-fixate from end of one sentence to the next. Patients with TBIs may also experience nystagmus, an ocular condition where the eye(s) drift off the target and then correct it to re-fixate resulting in continuous movement of the eye during fixation. This would reduce visual clarity and affect balance.
- Eye Focusing: Our eyes’ ability to sustain and switch focus between near and far objects are often damaged in patients with TBI. This can result in intermittent blurry vision, eye strain, headaches around the forehead, fatigue and inability to perform near work for a sustained period of time.
- Visual Perceptual Processing: Patients with TBI often report cognitive “fog” resulting in reduced visual attention span (ability to concentrate on the relevant visual information while ignoring other parts), visual processing speed (taking in and understanding visual information), visuo-spatial memory (recognizing your own environment and the spatial orientation of objects in there), and visual memory (remembering what you have seen before).
- Hemianopsia: This is when a patient suffers from a visual field loss where half of one’s visual field, either vertically or horizontally, is gone; the person cannot see it. Saccadic eye movement training (scanning vision therapy) can help restore some vision in patients with neurological vision loss.
Symptoms indicating a vision problem are most commonly experienced as:
- Blurred vision
- Sensitivity to light
- Reading difficulties; words appear to move
- Comprehension difficulty
- Attention and concentration difficulty
- Memory difficulty
- Double vision
- Aching eyes
- Headaches with visual tasks
- Loss of visual field
Neuro-Visual Rehabilitation is an individualized treatment program for patients of all ages, diagnosed with visual deficits as a direct result of physical disabilities, traumatic and / or acquired brain injuries. This includes visual problems caused by Traumatic Brain Injury, Cerebrovascular Accidents, Cerebral Palsy and Multiple Sclerosis.
Neuro-Visual Therapy is a process for the rehabilitation of visual / perceptual / motor disorders. It includes, but is not limited to, acquired strabismus, diplopia, binocular dysfunction, convergence, and / or accommodation, paresis / paralysis, oculomotor dysfunction, visual spatial dysfunction, visual perceptual and cognitive deficits, and traumatic visual acuity loss.
Very few in the health care professions, including head trauma rehabilitation centers, are adequately aware of visual problems resulting from Traumatic Brain Injury and the visual-perception consequences. Unfortunately, this creates a gap in rehabilitative services, resulting in incomplete treatment and frustration for the patient, family and treatment team.
The vision care professional can play an important role in the rehabilitation effort. Through optometric vision therapy and the proper use of lenses, a developmental optometrist is specifically trained to work with Traumatic Brain Injury patients.