September 23, 2019
Pondering Postural Control: The Visual System
We know that the visual system is complicated because we’ve discussed vision before. The Eyes Have It: The Foundation introduced the concept of functional vision and how the eyes and the head are intimately connected so there is a stable visual platform. The Eyes Have It: The Basics reviewed the basics of functional visual skills and contrasted these with visual acuity. Finally The Eyes Have It: Dynamic Systems At Work addressed assessing and training of vision and balance and an activity for integration of many senses with balance and movement.
Typically we use vision as our primary sensory information in the first years of life – up to about 6 years old. At that point, we begin to be able to pay attention to other somatosensory input (tactile and proprioception) as well as vestibular system information. Around 8 years old we begin to make more flexible use of the sensory information and we can re-weight input depending on the task, deeming some information more important to success than others. Finally around 12 years of age we learn to solve conditions of sensory conflict. Consider the classic example of sensory conflict: you are sitting in a train, looking out the window and the train right next to you begins to move. It takes you a moment to figure out that the other train is moving but you are not; this is sensory conflict.
Given how integral vision is to postural control, it’s amazing that we learn so little about it in most of our professional programs. I learned a great deal from generous OT colleagues and I also took several courses that dealt with functional vision – Astronaut Training and Eyesight to Insight were helpful. My favourite course is Seeing and Moving taught by my gifted friend, Kim Barthel.
I also remember that vision, while being essential to postural control, is also intimately connected to emotional arousal. We need a balance between peripheral vision (the “where is it” system) and central detail vision (the “what is it” system) to successfully navigate through space. However, if our emotional system is up-regulated and our brain thinks we are under threat, the “where is it” system becomes dominant and we miss necessary information for interpreting our position in space and navigating obstacles. Our balance and movements can therefore appear clumsy and uncoordinated.
There are options for treatment of visual challenges. First, treatment of emotional regulation is essential (we’ll be dealing with some concrete assessment and treatment strategies in a subsequent post). Next, training dynamic neutral alignment and then training visual tasks in this alignment goes a long way to improving vision for postural control. And don’t forget that our kids need to use their vision when they are standing and moving not just in sitting, so we need to train it in more positions/activities. Finally, there may be talented developmental optometrists in your area who are interested in partnering with you in the treatment of clients. Below is a picture of the cycle of vision therapy. Note the first step – gross motor control (balance and gait). I would suggest that PTs and OTs are essential team members in understanding vision and its contribution to postural control and movement.
Next up on Pondering Postural Control is Sensory Strategies.