(Relationship of TBI to Binocular Vision Dysfunction)
Traumatic Brain Injury (TBI) is a condition that afflicts thousands of people in the United States. There are a number of different symptoms and problems that are caused by TBI. Two of the more common symptoms are dizziness and headaches. TBI patients are frequently quite bothered by these symptoms, which precipitates extensive testing and evaluation in an attempt to find an effective treatment. These evaluations included multiple consultations (including neurology, ENT/ otology / vestibular specialists, PM & R, chiropractor, psychiatrist) and multiple tests (including CT, MRI, ENG / vestibular testing). They have tried multiple medications and therapies, but in many instances, have experienced minimal to no relief of their symptoms. It now appears that an uncommonly recognized vision condition – Binocular Vision Dysfunction (BVD) – is responsible for a large number of these patients’ symptoms of dizziness and headache.
Binocular Vision Dysfunction, Vertical Heterophoria and Superior Oblique Palsy
Binocular Vision Dysfunction (BVD) is a condition where the line of sight from one eye tends to be out of alignment with the line of sight from the other eye, making it difficult for the eyes to work together as a coordinated team. TBI is known to precipitate BVD. Two common forms of BVD are Vertical Heterophoria (VH) and Superior Oblique Palsy (SOP).
An important cause of VH and SOP appears to be a problem with the coordination of the two main eye aiming systems – the inner ear (or vestibular) system and the visual (or oculomotor) system. The inner ear system appears to be faulty and appears to be causing a slight misalignment, and if left alone, would cause double vision, which humans do not tolerate. To correct the misalignment and prevent double vision, the other aiming system (visual) moves the eyes in the other direction (i.e.- back toward their “correct” position). Then the faulty inner ear system acts again causing misalignment, followed again by realignment from the visual aiming system.
These repeating cycles of misalignment / realignment cause headaches and eye pain (from eye muscle strain and fatigue), and dizziness, lightheadedness, nausea, motion sickness and anxiety (from the back and forth eye movements).
Another way the body corrects the misalignment is to tilt the head toward a shoulder (this moves the image up in one eye and down in the other eye). However, this can cause chronic neck pain.
Those who suffer from BVD may also have other symptoms in addition to those of headache and dizziness:
- additional pain symptoms such as face ache, eye pain or pain with eye movement (symptoms similar to sinus problems, migraines, TMJ problems); neck ache and upper back pain due to a head tilt (similar to spinal misalignment symptoms);
- additional vestibular symptoms such as motion sickness, nausea, poor depth perception, unsteadiness while walking or drifting to one side while walking (“I’ve always been clumsy”), lack of coordination (symptoms are similar to those seen in patients with MS, sequelae of a stroke, an inner ear disorder or Meniere’s Disease);
- reading symptoms such as difficulty with concentration (symptoms are similar to those experienced with ADHD), difficulty with reading and comprehension, skipping lines while reading, losing one’s place while reading, words running together while reading (symptoms similar to those seen in someone with a learning disability);
- vision symptoms such as blurred vision, double or overlapping vision, shadowed vision (symptoms similar to those seen in patients with MS); light sensitivity, difficulty with glare or reflection;
- psychological symptoms such as feeling overwhelmed or anxious when in large contained spaces like malls or big box stores, feeling overwhelmed or anxious in crowds (symptoms similar to those seen in patients with anxiety or agoraphobia).
Some patients have few symptoms of BVD and are minimally affected, while others have many symptoms and are completely disabled.
Treatment of BVD
Patients must undergo a NeuroVisual Evaluation, which is detailed and thorough examination of vision, including assessment for small amounts of vision misalignment that are causing the symptoms of BVD (and that are not routinely identified on standard eye examinations). Problems with near vision, far vision and alignment will be corrected using glasses with aligning lenses, resulting in a reduction (or sometimes elimination) of symptoms.