BrainLine sat down with Dr. Gregory Goodrich to talk about the problems with vision that can arise after a traumatic brain injury. Dr. Goodrich is the supervisory research psychologist assigned to the VA Western Blind Rehabilitation Center in Palo Alto, California. He also serves as the program coordinator for the Optometric Research Fellowship Program at the VA hospital in Palo Alto.
BrainLine: How common is it to have vision problems after traumatic brain injury (TBI)?
Dr. Goodrich: For TBI in general, the literature says 20-40 percent of people with brain injury experience related vision disorders; however, the exact prevalence is not known. 1, 2
In the military population — although we don’t have a definitive statistic — we have found in mild TBIs that troops exposed to one or more blasts can have trouble with their eyes coordinating with one another, what we call “oculomotor or binocular dysfunction.”
In moderate to severe TBI, about one third of the troops tested have some sort of visual impairment, which can include visual acuity and field loss, binocular dysfunction, and spatial perceptual deficits.
Complete visual examinations are now a required part of testing for brain injury in all four VA polytrauma centers, which will help with data collection since, until this mandate was passed, comprehensive visual examinations were not an integral part of interdisciplinary protocols for brain injury. The hope is that in the future this comprehensive test will be part of any evaluation of someone with a TBI whether civilian or military.
BrainLine: What are the tests for visual problems like currently?
Dr. Goodrich: To date, if a person has a traumatic brain injury, he is not given a full visual examination. What is administered most often is a basic test called the Confrontation Visual Field Test, or CVFT. Basically, it consists of a doctor standing at arm’s length away from the patient, wiggling his fingers in different areas of the person’s visual field, and saying, “Can you see this?” This is a good, quick-and-dirty test, but unfortunately, it often misses significant visual problems.
Comprehensive visual examinations include the types of examinations you would receive normally for annual ophthalmological and optometric examinations. They look at eye health, refractive errors, visual fields, contrast sensitivity, and so on. What is unique about these comprehensive examinations is that they include examinations for occult injury, binocular function, and other specialized testing which goes beyond what is normally provided. In short, they are designed to detect vision disorders which are not commonly seen by clinicians and which require specialized testing to uncover.
Again, we hope that soon a complete visual examination will be a requirement of an interdisciplinary evaluation of someone with a TBI — civilian or military.
BrainLine: What are the most common kinds of visual problems?
Dr. Goodrich: The two big categories are visual acuity loss and visual field loss.
Let’s start with visual acuity loss. If a person wears prescription glasses and takes them off, he will have a loss of acuity — or clarity. With brain injury, people can have a relatively small visual acuity loss or significant loss.
Visual acuity loss results from damage to the eye, the nerve fibers that carry signals from the retina in the eye to the brain, or to the visual cortex. This loss can sometimes be effectively treated with glasses, magnifiers, or electronic reading aids such as closed-circuit televisions. How much the loss impacts an individual’s life depends on the degree of the loss. Needing a small amount of magnification is in some ways similar to those of us who need bifocals. A need for more optical magnification than that can require different devices and training.
Visual field loss is a bit more complicated. Think of your visual field as a pie. Visual field loss is categorized by which part of the pie is affected.
- If you have hemianopsia, half of your pie — or visual field, either vertically or horizontally — is gone; you cannot see it.
- If you have quadranopsia, a quarter of your visual field is lost.
- If you have homonymous hemianopsia, the same quarter or half is lost in both eyes.
- If you have bitemporal hemianopsia, you are missing the outer half (or inner half) of both the right and left visual field.
Hemianopsia and quadranopsia are the most common types of visual field losses; but going back to the pie analogy, other types of field losses include loss around the edges of the pie or loss from the middle going outward. And, of course, there can be differing combinations depending upon the individual injury.
Visual field loss is caused by damage to the nerve fibers that carry the visual signal from the eyes to the visual cortex and/or connect operations between different parts of the brain.
BrainLine: Are these vision problems temporary or permanent?
Dr. Goodrich: Just like people, all brain injuries are unique, and that includes the process of recovery; so it is difficult to generalize. After a brain injury, once the person is medically stable, we will start visual rehabilitation. If the visual problems resolve, great; if not, we have a head start by starting that early. Vision is integrated into other problems that can occur post-TBI like muscular imbalance and vestibular problems (dizziness, imbalance, vertigo, etc.)
BrainLine: Can people with brain injury suffer from both kinds of vision loss?
Dr. Goodrich: Yes, people with TBI can suffer from both visual field loss and visual acuity loss. After all, 40-50 percent of the brain is involved in vision; so if a person’s brain is damaged in a specific location or several locations, there is a high probability that his vision will be affected in some way.
BrainLine: If someone has hemianopsia, for example, and she can’t see the left side of her world, can she learn how to compensate for that, or “see” it?
Dr. Goodrich: Broadly speaking, there are two kinds of visual field losses — those with neglect and those without neglect, and this is a huge oversimplification but perhaps useful to begin understanding field loss.
Gregory L. Goodrich, PhD, Dr. Goodrich received his PhD in Experimental Psychology in 1974 from Washington State University. His career with the US Department of Veterans Affairs began in 1974 and he is currently supervisory research psychologist (Psychology Service) assigned to the Western Blind Rehabilitation Center.
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