What are the most common kinds of visual problems after a brain injury? Are these vision problems temporary or permanent?
The two big categories of visual difficulty after a brain injury 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.
Are these vision problems temporary or permanent?
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.)
Can people with brain injury suffer from both kinds of vision loss?
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.
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.