Given the time pressures and financial constraints many parents and school systems face, it is tempting to ask the developmental optometrist: “Can’t you just give me a bunch of activities for the occupational therapist to work on so I won’t have to come to your office for vision therapy?” I call this “The Wheelbarrow Approach”, and there’s a reason why it doesn’t work. The two therapies complement one another, but one does not replace the need for the other.
I was reminded of the integration between vision, as one of the key senses in development and learning, and vestibular as well as proprioceptive function, when I came across a wonderful review paper co-authored by one of my mentors, Dr. Harold Solan. It’ll be well worth your time to take a look at the paper here. One of the tests that Dr. Solan and his co-authors mentions is the Ayres Standing Balance Eyes Open vs. Eyes Closed Test. There are two different versions of this test, one from the SCSIT (Southern California Sensory Integration Test) and one from the SIPT (Sensory Integration and Praxis Test).
The key component of the test is having the patient stand on one leg, with arms either folded at the chest or resting on the hips, and recording the number of seconds during which balance can be maintained without either moving one’s arms to maintain balance, or touching the foot down. Our friend the gull, as pictured here, seems to do this easily but standing on one leg is not a natural act for most humans. What was the insight that Ayres derived through this test? Standing on one leg removes feedback to postural equilibrium through the motor end plates from one foot, which immediately places us in a position of postural sway. The ability to maintain oneself upright is increasingly dependent on anti-gravity mechanisms that help maintain center of gravity in the upright position. For most patients, the efficient way to do this is to transfer dependence from the proprioceptive system which has now become unstable, to a match between the visual and vestibular systems. This enables us to maintain alignment between the egocenter or midline of the body and the oculocenter. As far as the brain is concerned, the two eyes are combined in a cyclopean sense serving as a GPS or Global Positioning System of sorts integrated with the body’s midline. Close your eyes, and you lose this valuable feedback, leaving the vestibular system to rely on the unstable proprioceptive created by having one foot off the ground. Your brain directs you to put you foot down to re-establish your center of gravity. That is why everyone balances better, or longer, with eyes open vs. eyes closed. Or do they? Well, it’s fair to make that assumption for patients who are neurotypical. But most of the populations who both we and occupational therapists interact with are not neurotypical.
What does it signify if one’s balance time is no better with eyes open vs. eyes closed? It tells us that for this individual, visual feedback which normal partitions and distributes space to one side of the body or other is not helping to counteract postural sway. Which invites the obvious corollary: What does it signify if one’s balance is actually better with eyes closed vs. eyes open? That signifies that vision is not only lacking in terms of maintain one’s center of gravity within the body midline, but it is actively interfering. In essence there is a poor match between the egocenter and the oculocenter. What causes this to occur? That is the essence of the article by Dr. Solan and colleagues.
These insights gleaned through comparing Standing Balance Eyes Open (SBO) vs. Standing Balance Eyes Closed (SBC) are a fundamental reason when many developmental optometry procedures incorporate balance and movement. Research continues to support connections between persistence of primitive reflexes, muscle tone, postural responsiveness, and visuomotor coordination, as noted in a recent article by Klebzak and colleagues predicated on the work of Ayres that you can read here. It reflects the principles embodied in a quote attributed to the legendary optometrist Dr. John Streff: “When vision is working well it guides and leads; when it does not it interferes.”