Vision and eye problems are common side effects of traumatic brain injury. These issues can range in severity from mild blurriness to complete blindness.
Sometimes, a TBI can also affect the way your brain processes visual stimulus. This means that, although your vision may function fine, you might still struggle with depth perception or object recognition.
This article will explore the most common traumatic brain injury eye problems plus some of the best ways to treat them.
Causes of Traumatic Brain Injury Eye Problems
Vision problems after traumatic brain injury occur when the connection between the brain and eyes is damaged or lost. This can occur after damage to the eye structures themselves or to the visual pathways.
These pathways consist of cells and synapses that carry information from the eye to the visual processing centers in the brain. They include the:
- Optic nerve
- Optic chiasm
- Optic tract and radiations
For example, the nerve impulses from the retina travel down the optic nerve to the optic chiasm. From the optic chiasm, there is a “crossing over” of visual information, so that images from the right eye go to the left visual cortex and vice versa.
After passing through the chiasm, the impulses follow the optic tract and radiations until they reach the visual cortex, which lies in the occipital lobe. The visual cortex then transforms the neural impulses into images.
As you can see, vision is a complex activity involving multiple areas of the brain. Therefore, damage to any part of the visual pathways can cause eye problems.
Types of Traumatic Brain Injury Eye Problems
There are two primary types of eye and vision problems that can occur after traumatic brain injury:
- Neuromuscular eye problems. These impair your eye muscle’s strength and coordination.
- Visual processing problems. These cause your brain to no longer process visual information.
The following are some examples of eye problems that can occur after traumatic brain injury.
1. Visual Field Problems
Perhaps the most common eye problem after TBI is visual field loss. This condition refers to blindness in certain areas of your vision, such as your peripheral vision.
There are four main types of visual field problems:
- Hemianopsia – Half of your visual field, either horizontally or vertically, is gone.
- Quadrantanopsia – A quarter of your visual field is gone.
- Peripheral vision loss – The outer edge of your visual field is lost.
- Central vision loss – The middle of your visual field is lost, but the peripheral vision is fine.
Visual field loss is caused by damage to the visual pathways and certain areas of the brain. The location and extent of the damage will determine how much vision you lose.
For example, lesions on the optic nerve can cause central vision loss, whereas lesions on the optic chiasm typically cause hemianopsia.
2. Visual Scanning and Tracking Problems
After a traumatic brain injury, you can also experience problems scanning or tracking objects with your eyes.
This will make it difficult to read words on a page, for example, since the eyes will jump around to different words and lines instead of smoothly moving left to right.
One type of eye movement problem known as nystagmus can give you the feeling that the whole world is bouncing up and down.
Nystagmus is usually easy to diagnose because the eyeballs themselves are clearly moving, but sometimes doctors can only detect it through an in-depth eye exam.
3. Blurry Vision (Visual Acuity Loss)
Visual acuity refers to the ability to see clearly and to focus on an object. Visual acuity loss, therefore, causes blurred vision.
Blurry vision occurs after damage to the retina or the occipital lobe. Other causes of visual acuity loss after traumatic brain injury include:
- Dry eye
- Ocular migraines
- Detached retina
- Weakness in the extraocular muscles
Fortunately, most cases of visual acuity loss can be treated with glasses and magnifiers. If the brain damage was mild, sometimes visual acuity will also improve on its own once the nerve fibers heal.
4. Traumatic Optic Neuropathy
Traumatic optic neuropathy can cause both visual field loss and blurred vision, along with several other vision problems.
It typically occurs after an indirect injury to the optic nerve, such as a transmitted shock from an impact to the head. The optic nerve is particularly susceptible to shock waves, meaning that even seemingly mild bumps to the head can cause damage.
On an MRI, traumatic optic neuropathy might not be seen until 3-6 weeks after the brain injury, which can make it hard to diagnose.
Symptoms of traumatic optic neuropathy include:
- Partial or complete loss of vision, usually in one eye.
- Blurred vision
- Decreased color vision (dyschromatopsia)
Unfortunately, there is no proven treatment for traumatic optic neuropathy. However, some people do experience spontaneous healing, especially if the damage was mild.
5. Double Vision
Damage to the nerves that control eye movement will cause double vision. When these nerves malfunction, the muscles can’t move the eyes to focus on a single point. As a result, double vision can occur.
Sometimes the eye muscles will be so affected that the eyes become fixed in opposite directions (called strabismus). And sometimes there is only a slight alignment issue.
Interestingly, the brain can suppress vision from one eye to compensate for double vision and allow the person to see normally again. This explains why some people notice their double vision going away on its own after a while.
If this has happened to you, you should still go see an ophthalmologist right away. Even though it might seem like your double vision has improved, it really hasn’t. Instead you now only have vision in one eye.
Diagnosing Traumatic Brain Injury Eye Problems
An examination by an ophthalmologist is needed to fully assess a person’s vision problems, but basic tests can be performed by any doctor. Some of the exams doctors might perform to assess your vision include:
- Visual acuity tests. These are performed by holding a card or newspaper near the person and asking what they see.
- Confrontation visual field test. During this test, the doctor checks the patient’s ability to see all four vision quadrants by asking if the patient can see the doctor’s fingers in certain positions.
- Funduscopic examination. This test lets doctors see the optic nerve and confirm that the eye is clear of hemorrhages.
Finally, to test for traumatic optic neuropathy, doctors will check the patient’s pupillary response.
If one pupil responds slower than the other when light is shone on it, this is known as a relative afferent pupillary defect and is a strong indicator of optic neuropathy.
Treatments for Traumatic Brain Injury Eye Problems
Treatment will depend on the type and severity of vision defect you have. Some examples of treatment for TBI eye problems include:
- Eye exercises. These exercises engage your brain’s neuroplasticity and can help improve blurred vision.
- Scanning therapy. This therapy helps patients with visual field loss learn to compensate by scanning their environment more efficiently.
- Prismatic adaptation. During this treatment, the patient wears special prismatic glasses that shift the visual field to the right, forcing the person to look towards their left side in order to reach an object. It is effective for those with hemispatial neglect. This therapy helps retrain the brain to process vision on the left side. It works best when combined with visual scanning training.
To take part in scanning therapy and other treatments for traumatic brain injury eye problems, make an appointment with a certified vision rehabilitation specialist.
Even though they might not cure your vision loss, they can help make living with it a little easier.
Eye Problems After Traumatic Brain Injury
And that’s it! These are the most common eye problems after brain injury, and the best ways to treat them.
Remember, if you experience vision problems after TBI, the problem is most likely rooted in your brain and not your eyes.
That’s why your best option is to find a vision rehab specialist who can recommend the right treatment for you.
With the right approach, you can have a real hope of regaining at least some of your sight after brain injury.