Ординатура / Офтальмология / Английские материалы / Fixing My Gaze_Barry, Sacks_2010

then over time, you would associate sounds and smells from a given object with only one of the two images. When Sarah reached for an object, she reached for the “real” image. This is what happened to me when I was an infant. But I developed strabismus at such a young age that the second image actually faded from consciousness; I no longer saw it at all.

To make it easier to disregard one eye’s input, I turned in the eye that was not doing the looking. With my eyes in this position, an object would cast an image on the fovea of my fixating eye and on a nonfoveal region of the turned eye. As a result, the image seen by the fixating eye would appear clear, while the image seen by the turned eye would have less definition and detail. Under these conditions, it was easier to discount the displaced image from my turned eye, to regard its image as unreal. The more I turned in my eye, the less clear the image from that eye would appear, making it that much easier to ignore.

But why, my parents wondered, did I, like most infants with strabismus, turn the eye in and not out? Dr. Fasanella could not give them an answer then, but recent research has shown that young infants, even with normal vision, can move each eye more effectively toward the nose than away from it. Thus, if I needed to move one eye out of alignment in order to suppress its input, it was easier to do so by turning the nonfixating eye in rather than out. By crossing one eye, I could discount one image and see a single view of the world. This solved one problem but created another: I

had to develop a sense of depth without stereopsis.

Many scientists and physicians have assumed that a cross-eyed infant can still develop a good sense of depth using a cue called motion parallax, a way of seeing depth involving movement of the head. But this is not the case. People who have been cross-eyed since early childhood see much less depth using motion parallax than people with normal vision, and this, along with the lack of stereopsis, greatly compromises depth perception.

An easy way to experience motion parallax is to look out the window and slowly sway side to side. While swaying, keep your gaze fixed straight ahead. As you move right, near objects appear to move left while distant objects move with you to the right. The opposite happens when you move left. What’s more, near objects appear to move a greater distance than distant ones. The next time you are a passenger in a car, pay attention to the scenery as it rolls by. You’ll see that nearby objects appear to move away from you in a direction against the car’s motion, while distant objects appear to move in the direction of the car. The way these objects move relative to each other contributes to your sense of depth.

Since stereopsis and motion parallax play a major role in our perception of depth, infants with strabismus or other binocular vision impairments develop a sense of distance and space with an impoverished set of cues. They depend more on “monocular cues” to depth, such as shading and

perspective. As a result, many cross-eyed babies show delays in mastering tasks like grasping a toy or holding a bottle, and older children with the same problems may even show abnormalities in gait and posture. Finally, a loss of stereovision early in life leads to a greatly impoverished sense of distance and space. Of course, my parents didn’t know any of this when they first took me to see Dr. Fasanella. They knew only that they had a very temperamental two-year-old whose eyes wouldn’t stay straight.

After my first visit, Dr. Fasanella prescribed for me my first pair of glasses. They had heavy frames and were actually made of glass, not of the lighter, safer materials used today. My first childhood memory is of sitting on the stoop outside our kitchen feeling the weight of these glasses on my nose and ears. There was a rhododendron bush to my left that I wanted to look at, but I was afraid to turn my head for fear that the glasses would fall off and break. My glasses were bifocals, which made it easier for me to focus on objects nearby. If I’d had a particular type of strabismus called accommodative esotropia, wearing bifocals might have straightened my eyes. But even after several months of constant bifocal use, my eyes remained crossed. So, Dr. Fasanella decided to operate.

FIGURE 2.4: The six muscles that move the eyes. (© Margaret C. Nelson)

My first surgery occurred when I was twenty-eight months old. Dr. Fasanella explained to my parents that the eye muscles hold and move the eyeballs in their sockets (Figure 2.4). Think of my eye, he told my parents, as the head of a horse and the eye muscles as the horse’s reins. Imagine the horse’s head as pointing, let’s say, to the right. Shorten the reins on the left and lengthen the reins on the right and you can straighten the horse’s head. Dr. Fasanella realigned my eyes in their sockets by shortening the length of some muscles and changing the point at which they inserted into the eyeball. In my first surgery, he repositioned the right medial rectus muscle on the eyeball so that this muscle, which pulls the eyes in, was at a

mechanical disadvantage. He did this in an effort to decrease my tendency to turn my eye inward. He also repositioned the lateral rectus muscle so that it was more effective in pulling the eye outward. After the procedure, he noted in my records that further surgery would be required on my other eye “because of the large amount of esotropia.” Before my first surgery, he had warned my parents that more than one operation would be necessary. My parents trusted him and accepted his conclusions.

A year later, I had a second operation in which the corresponding muscles of the left eye were cut and repositioned in a similar manner to those of the right. As often happens with strabismus, vertical eye misalignments developed over time, and after the first two surgeries, my left eye gradually moved into a position higher than my right. So, when I was seven, Dr. Fasanella performed a third surgery to move the right eye upward. He also cut part of the tendon of the left medial rectus muscle to further weaken its ability to move my eye inward.

I remember my third surgery quite well. My hospital room was long and narrow with two beds, one for me and one for my mother. During my stay there, my mother’s friend Eppie came to visit. A nurse at the hospital, she brought me a set of finger puppets that I played with and treasured for years. Something about her was enormously comforting, wise, and warm. Many years later, I learned from my mother that Eppie, or more formally Florence Wald, was dean of nursing at Yale New Haven Hospital and had started the

first hospice unit in the United States. My mother remarked that even a seven-year-old child can recognize an exceptional individual.

When I was wheeled into the operating room, a man draped in a long gown came up to me carrying a narrow tube with a horrible stench.

“Do you like this smell?” he asked through his surgical mask.

When I said no, he told me that if I took ten deep breaths, the smell would go away. I eagerly breathed with him but only got to three before drifting out of consciousness. When I awoke in the recovery room some time later, I realized that the tube must have contained the gas that had put me to sleep. What was this business about taking deep breaths to make a smell go away? Why hadn’t he simply told me that the gas would put me to sleep? Did he think I wanted to be awake while Dr. Fasanella cut into my eyes? I felt betrayed.

I also awoke with an uncomfortable patch over my right eye, a patch that was changed every day for two weeks while I was confined to my bed at home. But there were compensations. I had always wanted a dog, and after my two-week convalescence, my parents surprised me by taking me to a neighbor’s house where they introduced me to a little puppy that became our first family pet.

My parents had such confidence in Dr. Fasanella, and I found him to be such a kind man, that the surgery itself

hadn’t frightened me. But I worried about going blind. On most nights throughout childhood, I woke up in the dark and checked for the familiar beam of light from a hallway lamp that would shine underneath my bedroom door. I would make sure I could see the light first with one eye, then the other. Once convinced that both eyes were still working, I quickly fell back to sleep.

After the operations, I certainly looked better. My parents and I were very pleased with the results. My eyes looked straight most of the time. Since I could keep my eyes aligned best when I looked upward, I tended to open my eyes wide with my eyebrows raised. I had large eyes in a small head, and this combination, along with the way I positioned my eyes, gave me the look of a startled bug. With my saucer-eyed look, school photos were always a problem. I tried so hard to make my eyes look straight in front of the camera that they ended up looking like they were popping out of my head. When I brought my class photos home, my parents didn’t comment on my bulgingeye look. Instead they purchased a set of my pictures, along with the much cuter ones of my brother and sister, and then quietly put all the photos away in a drawer. Kids at school called me “frog eyes,” but my parents and their friends told me constantly that my eyes were beautiful. So, despite my unflattering nickname and comical photos, I was happy with my straight, if bulging, eyes.

Even though my eyes appeared straight, I still didn’t use them normally. Dr. Fasanella told me that I continually

switched from one eye to the other. He called me an “alternator.” Had I used only my left or right eye most of the time, I could have lost vision in the unused eye. Since I alternated, I retained good acuity in both eyes. Dr. Fasanella seemed pleased with the overall result, so I felt proud of how well I had come through the operations. Although I was told that my depth perception was a little weak, no one explained to me that I lacked stereovision. My parents weren’t trying to hide anything; they simply didn’t understand what I was missing. So, I remained ignorant of this fact until that fateful lecture in college.

For me, cosmetic alignment of my eyes did not change the way I used them. I continued to see as I had before the surgery. This is true for many children with strabismus, particularly if they have surgery after the first year of life, the presumed critical period for the development of stereovision. Even though my eyes looked straight, they were not as straight as nature intended them to be. When my surgeon repositioned my eyes in their orbits, he had to be careful not to overshoot and turn me from a cross-eyed child into a walleyed youngster. So, after my surgeries, my eyes were still slightly crossed, although to the casual viewer they appeared normal. Given my former viewing habits, I was less likely to try to combine images from the two eyes and develop stereovision. I simply went back to my old way of seeing.

Like me, many strabismic infants and children require more than one surgery for adequate alignment of the eyes.

If a baby’s eyes are brought into closer alignment by surgery, yet the baby still can’t merge images, then he continues to receive conflicting input from the two eyes. To have clear, single vision, the baby must still suppress one eye’s input by turning in one eye once again or moving one eye out of vertical alignment, thereby defeating the results of surgery. Babies who can fuse images and develop stereopsis after surgery are more likely to keep their eyes aligned and require no further operations.

Had I seen a developmental or behavioral optometrist as a child, I would have been given optometric vision therapy. Ironically, at the time of my surgeries, medical doctors, developmental psychologists, and optometrists were working together at the Gesell Institute of Human Development right near the hospital where I had my surgeries. They studied and treated cross-eyed children. Then, as now, eye surgeons and optometrists didn’t generally communicate or work with one another, so no one mentioned the Gesell Institute to my parents. If they had, I might have learned how to coordinate my eyes for stereovision and avoided a third operation. Almost certainly, I would have had an easier time in school.

3

SCHOOL CROSSINGS

The most instructive experiences are those of everydaylife.

—Friedrich Wilhelm Nietzsche

I dreaded going to grade school. Throughout childhood, I had 20/20 acuity in both eyes, but I had trouble learning to read. When I looked down at the letters I on the page, they didn’t stay in one place. This problem grew worse as the print got smaller. My reading difficulties came to a head when I performed miserably on a standardized achievement test. These “objective,” scientifically designed tests were thought to reveal a person’s native intelligence. The tests were far more accurate, many school administrators felt, than the observations of a skilled, experienced teacher, even one who had observed a child for a full school year.

My school divided the children in each grade into four groups, and I began third grade in a class with all of my