You've probably heard at some point that "the eyes are the window to the soul". We also believe that the eyes are the windows to the brain. Interestingly, the eyes are actually the only visible neural tissue in the body.
For many functional neurologists, eye movements are extremely important in determining which networks in the brain are functioning well, and which may not be doing as well as they should. By taking a closer look at how the eyes are moving given a variety of different standardized tasks, we can come to a better understanding on how your brain is functioning.
Most people are familiar with an eye exam from an Optometrist, where visual acuity is the primary concern. While we are also interested in your visual acuity, we are especially interested in how the eyes are actually functioning. Think of it this way, if the eyes are essentially a camera, the brain is going to be the cameraman.
Eye Movement Exam
In a comprehensive neurological exam with a functional neurologists, a series of eye movement tests are administered. Typically, your physician will utilize a type of eye tracking software, such as VNG/VOG, saccadometery, RightEye, etc. This will then be cross examined with a bedside test by the practitioner.
The first part of the eye movement exam will typically begin with an assessment of what your eyes do when occluded. When looking at occluded vision, we are able to see what the eyes are doing when they're closed. Basically, what their default movement patterns are when there is nothing to visual fixate on or look at. Just from this simple test, your practitioner should be able to uncover a number of potential issues and causes to your symptoms. A few things your practitioner will be looking out for are: presence of nystagmus, excess saccadic eye movements, eye malposition, and pupillary diameter differences. These are the first building blocks to painting a thorough clinical picture.
The next test that you can expect is a pupillary constriction test. By testing the eyes' ability to constrict to light, your practitioner can help rule in or out many functional and pathological issues.
Convergence is typically performed next. This test is looking to see if your eyes ability to follow a target moving towards and away from you. This gives us a good idea of your brain's ability to perceive and depth. Some patients will have a difficult time with one or both eyes following the target moving towards them or away from them. This gives the practitioner more information on which nerves or nuclei may be contributing to your symptoms.
Next, one of the most fundamental of the eye movements will be examined: gaze stability. If a patient has gaze instability, they can struggle with multiple things. These symptoms can include fatigue, especially when reading or working on computers, concentration and attention issues, and even headaches and neck pain. Suffice it to say, making sure the eyes are stable on a stationary target may seem simple, but is of great importance.
After determining if the eyes are stable on a stationary target, we next need to determine if a patient is able to move their eyes on a moving target. This test is called a pursuit eye movement. In this task, we have the patient follow a moving target at progressively increasing speeds. There are many things we can determine from this test. If we see issues with pursuits, many times we see patient's who have difficulty with visual motion in their environment, eye fatigue, and focus issues to name a few. There are also many non-related eye issues that we can correlate to alterations in pursuit function, as they relate to dysfunctional areas of the brain.
Saccadic testing is the next eye movement we will test. A saccade is essentially a quick eye movement to a new target. This is the type of eye movement we typically use when reading. We can tell many things about brain function from saccadic activity, including: reaction time, accuracy, and coordination. There are many networks involved in a saccade, much like the eye movements previously listed, which includes the frontal lobe, cerebellum, and brainstem. Along with standard saccadic testing, we will also test something called an anti-saccade, which is where we have the patient look to a target equal and opposite to the novel target. This is a good test of choice reaction time, response inhibition, and decision making speed.
Our final test in our comprehensive oculomotor examination is the optokinetic test. This test is evaluating the reflexive stability of your eyes when present with visual motion. Many people who have issues producing this reflex will have difficulty with environmental motion. This may present as motion sickness, such as in the passenger seat in a car, on a train, or in an elevator.
Putting It All Together
The oculomotor component is one of the most important parts of your neurological exam, but is only part of an overall comprehensive exam to paint a vivid picture of the functioning of your brain. Once we are able to put all of the pieces together, we can articulate to you where we think the problem lies, and how we think we can help you. By creating an individualized treatment plan to correct the problems, we aim to rehab these pathways to improve your function and reduce your symptoms.
If you or someone you know is interested in a thorough neurological exam due to concussion, whiplash, migraine, or other neurologically based disorder, give us a call at (614)-706-2093 or check out our website: deltaneurohealth.com
