August 1, 2016

HOW FUNCTIONAL NEUROLOGISTS USE VIDEO-OCULOGRAPHY

Eyes are commonly known as the “windows to the soul.” If brain function can be considered part of your “soul,” then there may be more truth to the saying than you know! Eyes movement is controlled by six muscles, which make 5 different types of eye movement possible. Each muscle is controlled by different networks of the brain, so Plasticity Brain Center doctors can actually use eye movement to gauge your brain’s functionality in different areas.

How the Eyes & the Brain Parallel Each Other

The eyes are literally an extension of brain, in order to help its 3 main functions. If you remember from our previous posts, the brain has 3 purposes: perceive environment, interpret signals, and form a response. The eyes receive light signals in the retina, transduce them into electrical signals to the occipital lobe, and then the occipital lobe sends information to the frontal lobe for a response.

The frontal lobe, specifically our “frontal eye fields”, then produces 1 of 3 voluntary eye movements:

  • Fixate on the target
  • Track with the target
  • Jump to a new target

There are also 2 involuntary eye movements:

  • Optokinetic response
  • Vestibular-ocular response

The optokinetic response is what happens when you’re sitting still while the environment moves around you. Imagine being in a ride at Universal Studios, where you are stationary but an enormous TV screen creates the illusion of movement. The optokinetic response allows you to track the environment around you, even as it’s in constant motion, such as in a moving vehicle.

The vestibular-ocular response is what allows you to remain fixated on an object, even as your head turns. This ability is crucial for survival, as it allows us to remain focused on objects of interest while we are on the move. This helps whether we’re hunting deer, crossing a busy street, or reading in the car.

HOW WE USE EYE MOVEMENTS TO DIAGNOSE THE BRAIN

Every eye movement is processed by a different neuronal network, providing a powerful avenue for diagnosis. Our functional neurologists can measure each eye movement using well-established technology in new and innovative ways. One of our tools at Plasticity Brain Centers is video-oculography, or VOG.

VOG uses infra-red cameras placed inside a pair of goggles, pointed at a patient’s eyes. The patient will wear the goggles, which are hooked up to a computer and a TV. The TV projects a target that the patient will either fixate on or track, while the computer precisely tracks the movement of the patient’s eyes. Once calibrated, VOG provides a clear look at how your eye movement functions.

Functional neurologists also use a type of Virtual Reality technology to measure your optokinetic responses. When your brain does not track environmental movement accurately, you experience motion sickness, headaches, neck pain, fatigue, and other symptoms. Improving brain function and processing information accurately helps clients live more efficient and comfortable lives.

How Your Eyes Should Move

Our brain rehabilitation therapists utilize the VOG to measure how well your eyes remain still, as well as move. We can do this by covering your eyes and observing them with the infra-red cameras. If your eyes are not able to see or fixate on anything, they should remain still.

Brain problems may cause eyes to drift then suddenly correct themselves (nystagmus) or the eyes might shake in miniscule movements (saccadic oscillations). These eye movements may seem insignificant, but they are abnormal and indicate altered brain integrity.

At Plasticity Brain Centers, we also measure your “smooth pursuit eye movements” (or SPEMs in the medical world), which is how we track moving targets with our eyes. Similarly, our doctors will also track your saccades, or your fast eye movements. Saccades are so fast that they are actually “pre-programmed” by your brain.

SACCADES & BRAIN FUNCTION

Saccades are eye movements programmed from your brain’s environmental perception. Understand that your brain, with all of the information traveling to it, creates a full map of the environment around you. Even if you are not conscious of every detail, your brain includes them in the background of your awareness. A healthy brain has an accurate map, so when you suddenly want to fixate on an object of interest, your brain automatically aims your eyes exactly where they need to go.

Imagine trying to track a fly while it’s buzzing around a room. While you’re tracking it, you’re actually engaging your smooth pursuit system. If you lose sight of it for a second and then it pops up in your peripheral vision, your eyes will jump to it. This is a saccade.

If your saccades move too little or too far, it indicates that your brain is not functioning well, and your ability to interact with the world will be less efficient. This affects everyone, from children and adults that cannot read well, all the way to professional athletes that may not be hitting a baseball well any longer.

Our next blog will look more closely at saccades and saccadometry, or the measurement of saccades. Saccadometry measures saccades at 1,000 fps, giving our specialists an incredibly precise look at your eye’s speed and accuracy of movement. Check back next week to learn more!

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