Don’t let the picture scare you away from reading this. It’s easy to follow. Really. Easy, in fact, because its source is a wonderful paper entitled Effectively Reducing Sensory Eye Dominance with a Push-Pull Perceptual Learning Protocol based on principles that we know and love.
Published in a well-regarded journal, Current Biology, the paper is co-authored by Jingping Xu and Zijiang He from the Department of Psychological and Brain Science at the University of Louisville in Kentucky, and Teng Leng Ooi from the Pennsylvania College of Optometry at Salus University in Philadelphia. The concept of perceptual learning and neuroplasticity as applied to optometric vision therapy should sound familiar because our colleague, Dr. Fortenbacher and I have blogged about it.
So what’s the concept we already know that is virtually identical to the push-pull training that Xu, He and Ooi diagram above? It’s good ol’ MFBF – Monocular Fixation in a Binocular Field. (Okay, so it would be nice if researchers acknowledged that they’ve re-invented a clinical wheel. But let’s not get hung up in attribution of the concept – let’s embrace the support this research gives to the powerful mechanisms of MFBF.)
“Push-only training” is excitatory stimuli delivered through the weak or amblyopic eye, while the stronger or dominant eye receives no excitation. This is the approach taken when the only treatment for amblyopia is patching the better eye. “Push-pull training” is done with the weaker eye engaged in excitation while the stronger eye is simultaneously being inhibited. This is precisely what occurs in MFBF therapy, in which the weaker eye takes the lead, and the stronger eye comes along for the ride. This is commonly done in atropine penalization therapy, a passive pharmacologic version of MFBF, or more actively under anaglyphic or polarized conditions in vision therapy.
I reviewed the concept of MFBF as related to amblyopia therapy in a PowerPoint presentation included in an earlier blog entry during a seminar with SUNY Residents. Push-pull training principles go back to Schapero’s book on Amblyopia therapy 40 years ago, were popularized in an article by Dr. Allen Cohen, and detailed in a chapter on Amblyopia therapy in a textbook I’ve written – which is why all this is so near and dear to my heart.
The most exciting part of this paper is that the authors documented that push-pull training resulted in a learning effect on stereopsis, presumably through reduction on interocular suppression, even though the training stimuli carried no binocular disparity. We congratulate the researchers for re-discovering and applying the design principles of MFBF and bringing it to a wider audience of vision scientists in Current Biology. It lends further support to the power of optometric vision therapy.
– Leonard J. Press, O.D., FCOVD, FAAO