- Vision is Pervasive Throughout the Brain
- Pathophysiology of Acquired Brain Injury
- Two Subdivisions of the Visual Pathway – Parvo/Magno
- Interference in the Ambient Process – Significant Cause of Vision Problems in ABI
- Examples of Visual Skills that can be Affected in ABI
- Why Vision is a Big Part in Treatment
- Why Neuro-Optometrists are Valuable to a Rehabilitation Team
- Main Goals of Rehabilitation
- Areas that must improve in order to improve quality of life
- Get A Comprehensive Vision Evaluation By A Neuro-Optometrist
It’s estimated that there are between 2-7 million cases of head trauma each year
*51% Motor Vehicle
*10% Sports & Recreation
Remainder – Cerebral Vascular Accidents, Birth Trauma, Surgery, etc.
Every 15 seconds, someone suffers a head injury in the U.S.
Acquired brain injury is the leading cause of disability in children and young adults.
1 million children sustain a head injury every year
2/3rds of all persons sustaining head injuries are under 30.
Young men are 2x more likely than women.
75% of patients who survive head trauma and stroke need some form of rehabilitation.
A person with severe brain injury typically faces 5-10 years of intensive services.
The Cost – more than $4 million.
Only 1 out of 20 individuals with brain injury receive appropriate rehabilitation.
90% need visual care – Gianutsos
65% of the sensory information to the brain is visual and there are more areas of the brain dedicated to vision than all the other sense modalities combined.
There are at least 11 pathways from retina to brain which have been identified. All the visual pathways are parallel pathways – they both send and receive information. There are also effective feedback loops at all levels of the pathways.
The eyes don’t tell us what to see, the brain tells our eyes what to look for. – MacDonald
Visual processes are very involved and entwined with so many different other processes (auditory, vestibular, proprioceptive). There are more than 35 different areas in the brain identified as primarily involved with the processing of visual information and at least 305 intra-cortical pathways linking those 35 areas. Every lobe of the cerebral cortex is involved in visual information processing, and structures like the brain stem, pons, medulla, cerebellum, pineal gland are heavily involved in things like motor coordination and integration with the other senses.
The visual system is involved with processes such as balance, planning and executing motor movements, eye movement control, comprehending complex actions and ideas, sustaining attention, object identification, object localization and understanding the relationship between objects, filtering out irrelevant stimuli and memory.
Any disturbances to any of the 35 brain areas primarily or totally involved with the processing of visual information and any of the more than 350 intra-neural connections BETWEEN the 35 brain areas can cause symptoms and have an effect on visual comfort and visual information processing.
Anywhere you poke in the brain, you touch an area involved with vision. – Sanet
Research results at the cellular level following Acquired Brain Injury indicate that there is degenerative processes that occur in the CNS which can cause secondary damage that is NOT always proportional to the initial insult.
Mechanical stress (shearing) can cause ischemic changes and changes in receptor properties. Many times the injury is diffuse and minute and most often will not show up on x-ray, CT scan or MRI. Though injuries cannot be detected by current imaging techniques, in most cases they can still be devastating and significantly affect overall function. It is the abruptness of visual performance deficits resulting from ABI that makes compensation difficult.
There are two subdivisions of the pathway from the retina to the brain, the parvocellular pathway and the magnocellular pathway. The parvo pathway is also called the focal/central pathway. It is made up more from the macular and paramacular cells or the ‘What is it’ system. It is involved with seeing 20/20, and is detail and color oriented. It is slower to process and under more of our conscious awareness. The magno is also called the ambient/peripheral pathway or the ‘Where is it?’ system. It is made up of the peripheral retina. It is more under our subconscious awareness, involved with location of objects in space and their relationship to one another and movement detection.
Optimally, both the focal and ambient visual systems reinforce one another and function synergistically. A strong integration between our central and peripheral vision systems is critical for most of our daily tasks, such as reading and driving. Our side vision allows us to locate objects and process where they are in space, but our clear, central vision tells us what it is we’re looking at. When our focal (central) and our ambient (peripheral) processes are out of balance, it interferes with all aspects of performance.
A significant cause of visual difficulties in ABI is interference with the Ambient Process. Disturbances in the ambient process cause an inability to organize spatial information with other sensory-motor systems. Since the two pathways integrate together, if the ambient process is affected, the focal process is affected.
*Visual Acuity – clarity of sight
*Ocular Motility – eye movement control
*Binocularity – eye teaming ability
*Accommodation – focusing ability
*Visual Fields – peripheral vision
*Visual Midline – matching visual-spatial information with the body
*Visual-Motor Integration – vision guiding the intelligent movement of the body
*Visual Information Processing – making sense out of what is seen
*Visual Memory/Visualization – remembering what is seen
Due to the pervasive nature of vision, visual problems that can accompany head injury can be quite varied, even with similar diagnosis. Visual dysfunctions are often “hidden” in that they may not be obvious to the caregiver, or they may not be understood or adequately described by the patient.
Vision is often just thought of as seeing clearly and having a full visual field, so often the members of a rehabilitation team do not know that vision is affecting so many areas of function. Unfortunately, although 90% of those individuals receiving rehabilitation have vision problems, most rehabilitation teams do not include a neuro-optometrist.
Neuro-optometrists can evaluate the patient’s visual abilities and the effect that visual deficits are having on the patient’s overall rehabilitation process and include treatment plans to remediate or compensate for them.
Including optometric treatment such as lenses, prisms, filters, occlusion or neuro-visual therapy can significantly facilitate the progress of rehabilitation because many of the tests and treatment regimens by the rehabilitation team members are dependent upon the function and efficiency of the visual system. Since the visual system affects the input and output of information to the brain and motor systems, remediating the visual problems can often speed up the recovery process.
– To help the patient eliminate or compensate for visual problems
– To help the patient become more independent
– To help the patient re-enter their former occupation or to be trained for a new one
– To improve the patient’s quality of life (often by increasing the ability to efficiently perform activities for daily life skills)
*Visual function – oculomotor, accommodation, binocularity
*Visual Information Processing abilities
*Motor function – general movement abilities, bilaterality, eye-hand coordination, balance
*Attention – Especially Visual Attention
*Ability to filter and to integrate multiple stimuli
*Reaching a patient’s goals
If you or someone you know has had a head injury including seemingly minor jogs to the head, such as whiplash, concussion and sports injury, it could have affected overall visual function. If double vision was ever experienced or if academic, work or sports performance has been affected, we recommend making an appointment to thoroughly examine the visual system and rule out any visual insult that may have been incurred. Remember that not all optometrists work in this area, so it is important to seek out a neuro-optometrist for a specialized examination that will look at more than seeing clearly and eye health.