In between completing her work with other patients, Zelinsky would check in with Martha and review some of the data Martha had been collecting. After an hour Zelinsky had me move to her examination room and sit in the phoropter chair, where she began her own testing.
Figure 13: Fixation Disparity Test
One of the first tests Zelinsky gave me is called the Super Fixation Disparity Test©—named after its designer, Dr. Selwyn Super (D.O., F.A.A.O., Ph.D.).* Fixation disparity occurs when the two elements of binocular vision are out of sync.
To get the idea of fixation disparity, consider the circle on the left in Figure 13. Note that in the circle there are two vertical line segments—one in the top hemisphere, and one in the bottom. Using occlusions, we arrange it so that each line is seen by only one eye. The measure of misalignment is determined by how far these lines appear to be offset from each other. Testing for disparity is also done horizontally in the same way using the second circle.*
Some alignment disparity is useful as part of the design of the stereo vision system. If monocularly viewed targets are incorrectly misaligned when a person is attempting to view a scene in the real world, the binocular visual system can usually bring them into alignment and thus avoid double vision. But this is fatiguing, and causes cognitive difficulties—because we are continually refocusing on near and far objects throughout the day, and binocular readjustments have to be made each time. Zelinsky looks to see how much misalignment patients can tolerate in either direction before they lose the ability to synthesize a single stereo image from the two sets of input.
It is believed that in some cases, if such alignment is habitually too far off, the brain will simply shut down the confusing signals from one of the eyes. When this happens it may be true that cognitive functioning in the 3D visual/spatial “internal world” of symbols is also diminished, effectively reducing one’s ability to perform complex reasoning and problem solving.
Next, Zelinsky gave me the related Von Graefe Phoria Test. Similar to the Super test, Von Graefe measures the habitual tendency of the eyes to point inward, or outward, in the absence of a point on which they can both fixate. Phoria has implications for binocular vision, and the latency period during which the eyes are interpreting binocular visual signals. The test is performed using the phoropter by keeping the image for one eye still, and slowly moving another identical image until the subject reports them as being aligned.
On the Super Fixation Disparity Test©, which takes place in free space (e.g., as per discussion above, all of our “one hundred” imaginary pathways are available from the retina to the visual cortex), Zelinsky found that my overall habitual eye position was slightly outward, though still within the normal range. But on the Von Graefe Phoria Test, which blocks off much of the peripheral vision (so that now only “fifty” pathways are available), she found that my habitual eye aiming was perturbed: my eyes were pointed inward at a distance, and way outward when focused on close-up objects. This caused an exhausting lag in cognition as my eyes had to continually re-aim to avoid double vision. We can imagine the corollary of trying to follow a conversation between two people when, every time we shift our gaze from one person to the other, the audio lags behind the movement of their mouths for a second or two while we struggle to get it to catch up to their gestures.
Next, Zelinsky gave me a Visual Localization Test. In this simple (but in my case, ultimately quite telling) test, Zelinsky held a pencil so that the eraser was facing me, about twenty inches in front of my eyes. She said, “Look at the pencil. Then close your eyes and, without looking, reach up and touch it with your fingertip.”
She repeated the test with the target in a number of different positions, and also several times specifically had me reach across my body and touch the target with my opposite hand. Despite the theoretical ease of the task, I was completely unable to find the eraser tip of the pencil, with my eyes closed, in any of the positions, helplessly waving my finger around in space until I accidentally hit the target.
In general, a subject’s inability to touch the eraser can be caused by three distinct failures. First, the subject may simply not know where the eraser is; his central vision allows him to see it fine, so he knows what it is, but his peripheral vision does not allow him to find it in space relative to his body. Second, the subject might know where the eraser is—his peripheral vision is working fine—but he doesn’t know where his hand is. For example, if the subject can reach the eraser on his right-hand side with either arm, but not when the eraser is on his left-hand side, the problem is likely with his visual processing. If the subject can accurately locate the eraser on either side with one arm, but not the other arm, then the problem is likely with the proprioceptive signals coming from his body. Or, third, in the worst case, he could have problems with both.
In my case, the vision signals going to my visual cortex were fine (eyesight)—this was not the problem. Thus we knew that it had to be the signals coming from my muscles, the “where I am” sense, which were not getting through correctly to form an accurate body image in my brain. Zelinsky had two additional clues in interpreting this failure: first, she noted that my severe neck and head pain suggested a compromised motor response sending conflicting signals to my various neck, arm, and back muscles; and second, Martha had noted the ATNR present when I turned my head, indicating that my neck was not operating independently of my shoulders.
Zelinsky followed up with a Confrontation Visual Field Exam. She held her hand out to the left side of my head, outside the range of peripheral vision, and said, “Cover your right eye, look straight ahead at my eyes, and tell me when you see my fingers moving.” She began wiggling her fingers, at the same time slowly bringing her hand toward the center of my face. As soon as I signaled that I could see her fingers wiggling, she repeated the test on the other side. Zelinsky was determining the volume of space to which I could attend, and was measuring the signals going into my visual system, looking for possible damage to my ganglion cells.
Because I had performed well on the H-pursuit test, successfully anticipating the movement of the pencil through the H pattern in the normal way, because my King-Devick Test was normal, and because I demonstrated normal peripheral awareness on the Confrontation Visual Field Exam, Zelinsky knew that the problem was not likely to be with the eyesight system itself.
Lastly, Zelinsky took me through her patented Z-Bell™ Test. The first time one experiences this test, it is quite stunning, and seems almost impossibly magical. While I was sitting in her optometry chair, Zelinsky said, “Close your eyes. When I ring the bell, reach out and touch it with your finger.” After my eyes were closed, she brought out a series of differently pitched bells and rang them in various quadrants, high and low, left and right. The test feels weird because, with your eyes closed, you can’t see anything, so it seems as if you aren’t “using” your eyes. And yet, depending on which lenses, tints, and occlusions she uses to alter the light striking your closed eyelids, sometimes your hand just waves around helplessly, but at other times you can “feel” exactly where the bell is, and touch it—like feeling the “power of the force” in a Star Wars movie.
The key to making sense of this test is in understanding that when the patient’s eyelids are closed, no eyesight images are registering—he can’t see—but a significant amount of light is still passing through to the retina. The non-image-forming retinal systems operate with minute levels of light, so they are not affected. In this way we have a quick and easy filter—the eyelids—so we can test the effect of different lenses on the non-image-forming retinal systems, without distraction by the two eyesight systems. We can think of the Z-Bell™ Test as a sort of “vision” test but for non-image-forming retinal processing. This is crucial, because it allows an optometrist to align her patient’s three-dimensional hearing with his internal visual/spatial map of the surrounding space.
Zelinsky often repea
ts the test a number of times during the final phases of tweaking prescriptions for eyeglasses, typically using the phoropter, but sometimes with handheld lenses and filters. Among the treatments she is testing are colored lens filters, prisms, lens prescriptions (possibly including, very specifically, nontraditional balance between the lenses), and translucent occlusions (translucent film applied to the lenses to block, or partially block, light), all later built into the glasses that she prescribes.
The Z-Bell™ Test, already mind-bending to experience yourself, is perhaps equally electrifying to observe. I’ve now many times watched others being given the test, and what you see is that for one of the bells the patient is waving his finger around eight inches away from where the bell is ringing. He can’t find it at all. Then, with just the slightest change in tint, or lens, he is able to touch the bell, right on target, every time.
With no glasses on, and also with my normal prescription glasses for mild nearsightedness, in bright light (and, remember, with my eyes closed), I was not able to touch any of the bells in any of the quadrants on the Z-Bell™ Test. This was a potential explanation for my great difficulty turning sounds into the visual symbols of thought, and also for my extreme aural sensitivity. Because my visual/spatial system was so degraded, I had to increasingly rely on my audio processing. But, as the Z-Bell™ Tests showed, the 3D spatial world of my hearing was completely out of sync with my 3D visual world, creating an impossibly complex stream of input data that my brain had to disentangle throughout the day. (And we should note that, because of my aural predisposition, and my lifelong study of both sound and music, this integration was much more central to me than it typically would be for others.)
Zelinsky also took me through an exhaustive set of vision tests, such as you might get—in abbreviated form—at a regular optometrist’s office (“Which is clearer, A or B?”). Ultimately, she would be prescribing partly for my eyesight, and this had to be taken into consideration, although in my case it was clearly secondary to prescribing for my brain.
Her diagnosis: Except for minor problems with floaters from the crash,* my eyes themselves were working fine. Additionally, the chemical and electrical “magic” that performed the filtering in my retinas was also in good shape, so the reduction from 100 million retinal receptors to 1 million axons was happening correctly. The problem was in my brain. Zelinsky now weighed her options:
1. With the eyesight part of any prescription she decided upon, she could affect the relationship between target (center vision, attention) and background (peripheral vision, awareness). She could blur the target so the background was emphasized, or vice versa. The balance between the two would affect my executive function (i.e., planning and problem solving). She also could make changes in my intentional eye movements, such as where I chose to look within a scene.
2. With nonyoked prisms, she could affect my peripheral awareness processing, and make changes in my anticipatory eye movements, such as when I was automatically predicting the motion-path of an object.
3. With yoked prisms, she could affect my postural mechanisms, and make changes in my orienting movements, such as when I turned my head in response to a sound.
4. Using filters, such as tints, occlusions, and the blockage of tear duct drains (tears change the way light gets through to the eye and also help regulate body systems), she could affect the homeodynamics of my body, and make changes in my reflex movements, such as those driven by states of vigilance. For example, there are direct connections between the retina and the hypothalamus, which affects emotion states.
One of the principles of Zelinsky’s treatment involves making an additional determination of how much discomfort and challenge a patient can tolerate. Mostly this has to do with the wiring between the eyes and the brain, and is beyond the control of the patient. However, some of it has to do with temperament and how much the patient will work with the lenses to push the brain into using new neural pathways. Often Zelinsky will have to “pry open a small window” in which to work with an early prescription, and then follow up later with a more brain-challenging prescription to get the real work done. With some temperaments, she has found there is not much she can do.
Additionally, any plan Zelinsky formed would, like the plans of Donalee, be both long-term in nature and comprehensive, rather than isolated to a specific condition or problem. In my case, this meant that her plans included fixing processing weaknesses that were present prior to my brain injury.
After looking over all the data before her, including my extensive self-reporting notes, Zelinsky made her decisions about treatment. Importantly, she assessed that I could tolerate a lot of discomfort, and also that I was highly motivated to change. She would intentionally push me to the edge of her working window, and would plan on using a series of prescriptions to move me from one phase of brain reconfiguration to the next. I would continue to work with Donalee to exercise my brain and push it to take advantage of its new cognitive capabilities as I progressed with my glasses.
Because I was completely absent the abilities to multitask and plan, Zelinsky felt there were immediate problems to be addressed in my executive functioning. And she also wanted to address serious problems with sensory integration—specifically between my eyes and my ears. She decided that she would work with my “good side,” and angle the light from my right (that is, bend the light so that it tended to strike the nasal part of my right eye, and the temporal part of my left eye). For this she used very slight lateral, directive, yoked prisms (0.5 prism diopter in both lenses, with the thick part on the left). But, as noted above, even this very slight prescription was enough to make major changes in which cells of the retina were processing the light. In retesting me on the phoropter, and with handheld lenses, the Z-Bell™ Test showed me right on target, suggesting that she had found some good pathways through the brain with which to work, and that my eyes and ears were now synchronized.
I was mildly nearsighted, and ordinarily would have been given a slight corrective lens in order to see better. But instead of correcting me to 20/20, Zelinsky wanted to stabilize the background of my eyesight—the peripheral, context-setting vision (in contrast to the central target vision)—so she made the lenses slightly thicker in the center, and thinner on the edges. This scattered the light so that it was dispersed toward the corresponding edges of my retinas, which in turn emphasized my background retinal processing, and deemphasized the target. Zelinsky knew that when I focused on the target I lost my ability to organize the scene surrounding it (such as what happened to me in Home Depot). She wanted me to get more of the context, more of the “bigger picture” of the world around me, and not take in so much of the detail.
This second part of Zelinsky’s prescription was intended to address the problems I had when I would become overwhelmed with the details of a visual scene, completely unable to create any gestalt meaning of the larger objects the details comprised: parking lots after shopping, food items on grocery store shelves, and so on. In the diary notes that follow, however, we will also sense my frustration at the necessary (for the moment) diminishing of my central vision.
In the initial days after I began wearing my first pair of glasses I went through all sorts of extreme body and sensory changes, both before and after the Ghost showed up. Having found healthy brain tissue with which to work, I was now relearning how to interpret the signals coming in—like a baby exploring the world. This explains the thrashing that I was going through at the time—waving my arms around in wild gyrations, and dancing, just to walk down a hallway—and the low-level chaos I was experiencing with the apprehension of lines, and doorways, and stairs in my environment. But despite the constant effort, I felt good, and was figuring it all out as my brain rewired itself.
In addition to the phenomenon of the Ghost appearing—which one of Zelinsky’s interns suggested might have been partially caused by some strange form of Charles Bonnet syndrome*—there were many oth
er odd things happening to me as well. I took extensive diary notes throughout my treatment with Zelinsky. Following are some entries starting in the first week of having my Phase I glasses:
February 8th–25th, 2008: I love the greatly expanded hearing landscape I have with these glasses, especially on the left, but I have also considered these to be the glasses from hell! It is hard for me to keep wearing them. They make me so tired, and I am always on the border of losing my balance. I find myself shouting “I can’t see!” (silently, inside, but also sometimes even vocally, out of frustration) as I try to make sense of the hugely changed world around me.
I am constantly hungry, with an incessant craving for sugar and carbohydrates. In the very few times I have taken the glasses off for an hour or so, the hunger recedes. I am gaining weight (two pounds a week), but also feel that I am consuming many more calories than that.
I am experiencing mild nausea, and mild disorientation much of the time.
I have taken to wearing the glasses twenty-four hours a day (that is, I wear them also when I sleep) because I have found that with the highly visual nature of my dreams, without the glasses, I regress by the time morning comes. Wearing the glasses at night allows me to dream without visual fatigue, and I feel much better in the morning.
The glasses have felt “right” (correct) in many profound ways. And yet it is true that, especially early on, at times I have been frustrated to the point of yelling out loud, although even at the time it was happening I couldn’t quite describe what it was that was so annoying to me. It was like everything was working correctly, but it was all so new, and I could not make sense of the world around me in the usual way.
The Ghost in My Brain Page 22
