Got my copy of the new book by Padula, Munitz & Magrun from OEPF in the mail yesterday, and what a treat it is! I have all three editions of Dr. Padula’s Neuro-Optometric Rehabilitation, the forerunner to this new text. I haven’t compared them side by side to see what’s new, preferring instead to read through it with fresh eyes (or should I say, with fresh visual systems?). I’ll have more insights to share as I proceed through the book, but there’s so much to savor that I’m digesting it in small bites. I’ve blogged before on some observations about yoked prisms, but on p. 21 of this book Raquel Munitz, MS, COVT, relates a concept I haven’t heard of or seen in print before. I’m going to share it with our staff today and we’ll see what our experiences are putting it into our therapy rooms. The concept is yoked prism rock. In fact, it’s theme dovetails with the new video “Call AVTC” from our colleagues at Alderwood Vision Therapy Center in WA (Alain, you are a wicked good writer and director!).
Raquel writes that individuals who have adapted their previous movement in space according to a distortion in the appreciation of space will find the experience of a new visual orientation to be very strong. The experience of being “rocked” with different base sets of yoked prisms sets a new standard for visual-motor orientation, ultimately resulting in greater postural freedom.
Take for example someone who does not have an good internalization of right/left orientation or differentiation, such as a child who confuses right/left contributing to spatial uncertainty and letter reversals or transpositions in words. This child can be “rocked” with lateral yoked prisms to match kinesthetic sensation with transient visual distortion, identifying and feeling the direction in which space is shifting.
In our practice we’ve used prisms on a monocular basis as “loose prism jumps” to develop increased sensitivity to JNDs, or Just Noticeable Differences in spatial shift — up/down/left/right and vectors. But I hadn’t previously thought about the application of yoked prism in flipper form to rock the patient’s orientation and establish greater postural freedom, as Ms. Munitz labels the process. When we place yoked prisms on a patient we use an informal version of Dr. Kaplan’s Yoked Prism Behavior Inventory. We often look at performance without prisms, then apply the prisms and re-assess. The relationship of yoked prism rock as compared to performance through one direction at a time should provide different insights and results, much as there is difference in concept between vergence facility and vergence amplitude. I anticipate that yoked prism rock vs. static yoked prisms are complementary processes in handling visual space that interact in ways that wouldn’t be totally predictable until one tries it with individual patients.