Two Eyes, Two Bodies, Different Skills?

You know that feeling when you are taken so much by surprise by something that you think, “Wow,” but on the other hand when you consider the explanation for the occurrence you think, “Well, of course!”?  This was my reaction recently during a vision therapy session with M, one of the cases I introduced in my last blog.  (So if you haven’t read it, go back and read that one first….this one will be more meaningful.)

A couple of the visual skills I often look at of each eye individually are fixation stability and saccadic movements.  Fixation stability refers to the ability to look directly at a point and maintain that as long as desired without an involuntary drifting or shifting away from the intended point.  This can be impacted by a processing skill known as visual attention; an eye will only look at a point if the brain is telling it to, and can be controlled both voluntarily and involuntarily.  Additionally, the control of the striated muscles around the eye, known as extraocular muscles (EOMs), is critical.  Saccadic movements are changes in fixation from one point to another.  Accuracy of these movements depends on visual attention, control of the EOMs, and correct spatial judgment of the location of the new point relative to the point the eye is already fixating on.

M is extremely left eye dominant, although the right eye doesn’t have any structural or health reason for this.  She is able, with correction, to see 20/20 in that eye, but sees 20/20 without any correction in the left eye.  Over the past couple of years she has developed fluctuating, intermittent nearsightedness in the right eye (so she doesn’t see far away as well without correction) and that eye occasionally turns inward.  M will tell you “I really only feel my left eye working” and has recently developed good awareness of when the right eye is “on” and when it isn’t.  Has the word “instability” come to anyone’s mind yet?  It should.

To enable two eyes to work well together, each eye must become as equal in all skills as possible.  So as we were working on the skills of fixation and saccadic movements with each eye separately, a really amazing thing happened.  While using only the left eye, she could hold fixation very easily.  Her saccades were not perfectly accurate, but she could see the error, make an adjustment and make them accurate.  She could do this either in left stance (L AFIR for all you PRI lovers) or in right stance (R AFIR).

The right eye was a different story.  In right stance she could not keep her fixation from sliding off target to the right after a few seconds.  Additionally, her saccades were consistently inaccurate, and she had a very difficult time making an appropriate adjustment.  In left stance, her fixation was easier to control and she could make adjustments to her saccades more readily.  She still struggled with the two skills, but her ability to control and modify them was much better.  We repeated this in right stance again, to see if there was just a learning curve involved, and the result was the same as the first time:  much harder.

This was the moment in time when all I could do was think, “Wow, did that really just happen?”  Then my surprise subsided so I could reason:  M developmentally has not had good binocular (eye teaming) skills, nor has she been able to stay reciprocal in her gross motor function.  Based on Postural Restoration philosophy, her developmentally dominant right-sided body is reflected in her habitual pattern of movement, breathing, sleeping, and anything else you can name, including eye movements (as we know from our work in PRI Vision).  Since her right eye has not been as active in the brain as the left eye, it would stand to reason that it would be less accurate in fixation and movements, according to optometric tenets.  This is part of her developmental pattern, inter-woven and embedded in the brain with her other patterns of movement, etc.  This integration of the patterns is what we believe in so strongly in PRI Vision, from the way the eyes move, to the way the brain processes information from them, and even characteristics of a person’s prescription.  Putting her in appropriate L AFIR (specifically left stance without inappropriate extension tone) allows her to be in a different pattern than she developmentally operated in, so by linking the visual skill with a new body pattern she is able to make changes more readily than if positioned in the old pattern.  “Well, of course!”

This presents an entirely new dimension and challenge to the world of vision therapy.  Most of the typical activities in vision therapy are done seated.  In more developmentally or sports-performance based programs, standing is more common.  If the patient is standing, either no indication as to desired “posture” is given in the instructions, or words like “balanced”, “good”, or “relaxed” are used for the posture description.  For an optometrist, what do any of those really mean?  Even for many who are in physical disciplines?  This might explain why some vision therapy patients are not as successful in their programs as others, or why some do very well in the therapy room but have trouble translating the skills to every day life for meaningful use…. along with many other potential less-than-maximum outcomes.  Here’s the most alarming thought:  what if the new visual skills are all being learned while the patient is positioned in too much extension tone, which means to use them, the patient must continue to operate with that same extension tone? (Hebb’s Law–Neurons that fire together, wire together.)  I know all the PRI-minded readers are thinking “Oh my!”

As behavioral/developmental/neuro optometrists, we talk often of looking at the patient as a “whole”.  I know that as an optometrist, I am limited in my knowledge base that allows that to happen most effectively.  Becoming more integrative is essential for allowing two eyes to work with each of the two (halves of the) bodies, and develop, and meaningfully use the same skills, all while not locked into a state of too much extension, but rather in a state of PRI-defined neutrality.

Keep moving beyond sight…

Dr. Heidi

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