One of the most challenging aspects of vision therapy is designing procedures that provide good feedback on when patients are truly processing with both eyes simultaneously. The patients that have the greatest need for these procedures are those with strabismus, usually detected by motor misalignment of the eyes, or the eyes not being simultaneously aimed at the same point. In some cases, particularly after eye muscle surgery, the eyes may look cosmetically aligned, but still aren’t functioning synchronously in the brain. By that we mean that the vision perceived through one eye is out of phase with information coming through the other eye.
An article that recently appeared in the journal Optometry and Visual Performance reviewed the applications of what I termed Press Lites. That article provides background information for what you’re about to see, so be sure to read the article here. On page 66 you’ll notice that I refer to a procedure that involves using two lights, one red and one green, that blink alternately and have to be processed in a synchronous way. Dr. Daniel Press just emailed me a video that perfectly captures the procedure, so take a look at it and then I’ll explain.
Note that the playful spirit that Matthew exhibits, and the ability of Dr. Dan Press to orient him to the procedure is a great example of the discovery component of vision therapy that is so important in feedback and awareness. With the red/green or anaglyphic glasses in place as pictured, the glow stick on Matthew’s right is green and can only be seen by the right eye, while the one on his left is red and can only be seen by the left eye. How do we know when Matthew is processing with both eyes simultaneously rather than alternating rapidly between the right eye view and left eye view?
There are many targets such as the one pictured here, that have some portion of the field seen by the right eye and some portion of the field seen by the left eye. Although we ask the patient questions about what she or he is seeing, we often lack the ability to judge whether both eyes are operating synchronously or by taking turns. The patient might be able to identify a sequence of words or other stimuli, but one eye is still functioning independent of the other eye. Part of the problem is that most vision therapy targets are static, and many real world stimuli are changing over time or dynamic. The targets lack motion that can be judged in real time.
Notice, in contrast, something special about the what’s happening with the lights in the video.
At first the lights are flashing out of phase, and Matthew is instructed to report when the lights are flashing at the same exact time, or in phase. He gets it, but playfully says “now, now, now, now, now” – and the doctor says not any more — do it again, tell me when they’re flashing at the same exact time. He looks, but is late and says “now”, when the lights are out of phase instead of being in synch. He’s prompted to look again, and complemented for getting it right on. He has to demonstrate that he can do it at least twice consecutively to know that he didn’t just get lucky the first time.
Notice how engaged Matthew is as he settles into the visual requirements of the procedure, and note the joy in the doctor’s voice as he guides Matthew through the process. This is the spirit of Liberty Science Center at its best. Although we’ve billed this as an “anti-suppression” procedure, the activity is based on real time changes that encourage the two eyes to stay in phase as they build rhythmicity and periodicity. In other words, they’re learning how to entrain each other in the brain over time. After awhile it feel good for the two eyes to be in synch, much like it’s exhilarating for the two feet to be in tandem while turners are turning a jump rope in time.
Realize something else. To maintain both eyes in phase not only builds synchronicity between the eye’s two channels in the brain; it builds a significant reservoir of sustained visual attention. In and of itself, that is very valuable.