Fixing My Gaze

But all in all, she said, she got along perfectly well—she drove a car, she could play softball, she could do whatever anyone else could. She might not be able to see depth directly, as other people could, but she could judge it as well as anybody, using other cues, such as perspective, occlusion, shading, or motion parallax. It was no big deal.

I asked Sue if she could imagine what the world would look like if viewed stereoscopically, and she said, yes, she thought she could—after all, she was a professor of neurobiology, and she had read plenty of papers on visual processing, binocular vision, and stereopsis. She felt this knowledge had given her some special insight into what she was missing—she knew what stereopsis must be like, even if she had never experienced it.

But in December 2004, almost nine years after our initial conversation, she wrote me a letter, which began, “You asked me if I could imagine what the world would look like when viewed with two eyes. I told you that I thought I could. . . . But I was wrong.”

She could say this with some conviction because she had suddenly, unexpectedly, acquired stereovision herself, and the reality of this, the actual experience, was utterly beyond anything imagination could have conceived. She was almost fifty and had been having increasing visual difficulties resulting from the misalignment of her eyes. Finally, she had embarked on an intensive course of training with a developmental optometrist, and one day, after learning to align her eyes, she suddenly saw the steering wheel of her car “popping out” from the dashboard. After having lived in a flat world for fifty years, Sue felt this sudden leap into three-dimensionality as a revelation. Her world was now full of a new sort of visual beauty and wonder so deep that three years later, when she wrote to me, she was still enraptured with it.

“My new vision continues to surprise and delight me,” she wrote.

Most of the phone calls and letters I receive are about mishaps, problems, losses of various sorts. Sue’s letter, though, was a story not of loss and lamentation but of the sudden gaining of a new sense and sensibility and, with this, a sense of delight and jubilation. Yet, her letter also sounded a note of bewilderment and reservation: she did not know of any experience or story like her own and was perplexed to find, in all she had read, that the achievement of stereoscopy in adult life was “impossible.”

Indeed, what Sue described to me in her letter went completely against the current dogma of “critical periods” in sensory development—the notion that stereoscopy (like many other aspects of visual perception, and like language, as well)—had to be acquired in the first three or four years of life, or it could never be acquired, for the critical brain cells and circuitry needed for stereovision would fail to develop.

Long suspected by surgeons operating on children with strabismus, this notion of a critical period seemed to be confirmed by the famous experimental work of David Hubel and Torsten Wiesel, who showed that if kittens were rendered strabismic by detaching an eye muscle, binocular depth cells would fail to develop in their brains, and they would lack stereovision. It was only when Sue learned of these experiments—she was a college student at the time—that she realized she herself might be stereoblind, like the kittens. This, indeed, is the vivid opening scene in her narrative:

When Sue next went to her eye doctor for a routine check, she asked him to check whether she had stereovision. He brought out a stereoscope and test stereo pictures. Sue could not “get” any of them, could not imagine what “getting” them would be like. Would it be possible for her to gain stereovision, she asked? The doctor replied, no, it was much too late, and added, “Stereopsis is just a little fine-tuning for the visual system. You don’t need stereovision because you don’t have stereovision.”

Sue accepted that she would never have stereovision and got on with her life, becoming a teacher and researcher, marrying, and raising a family. Somewhere, at the back of her mind—for she is a scientist and incessantly curious about how the world works—was a question: what could stereovision be like? And yet, her life, visually and otherwise, was full and rich, and she did not “miss” stereo or think of it too much. So thirty years later, when she finally sought vision therapy and unexpectedly gained stereovision, this came as a bonus, a miraculous complement to her other visual improvements.

Sue exulted in her newfound sense of stereoscopic depth. She found it much more than “fine-tuning”—it was an entirely new way of seeing. “People who have always had stereopsis,” she said to me, “take it for granted. They have no idea how wonderful it is. You have to have been stereoblind for half a century and then acquire it to value it properly.”

How was Sue able to acquire, essentially, a whole new sense so long after the “critical period”? I was as puzzled by Sue’s story as she was. And I was intrigued, for I myself had never taken stereoscopy for granted. On the contrary, I was something of a stereophile, having played with 3D drawings and Victorian stereo viewers as a child and later experimented with stereo photography. So I arranged to meet Sue again, and this inspired me to write an article about her experiences in 2006.¹

But that was not the end of the matter.

All that Sue intimated to me in her letters and conversations has now been expanded and deepened into a fascinating account. Fixing My Gaze is a beautiful description and appreciation of two very distinct ways of seeing—with and without the benefit of stereoscopy. But it is also an exploration of much more. Sue is at pains not only to present her story in clear, lucid, often poetic language, but also, as a scientist, to provide explanation and understanding.

She is in a unique position to do this, drawing on both her personal experience and her background as a neurobiologist. She has interviewed many eminent vision researchers and pondered the problem of critical periods with them. Her experience indicates that there seems to be sufficient plasticity in the adult brain for these binocular cells and circuits, if some have survived the critical period, to be reactivated later. In such a situation, though a person may have had little or no stereovision that she can remember, the potential for stereopsis is nonetheless present and may spring to life—most unexpectedly—if good alignment of the eyes can be obtained. That this seems to have happened with Sue after a dormant period of almost fifty years is very striking.

Although Sue originally thought her own case unique, she has since found a number of other people with strabismus and related problems who have unexpectedly achieved stereovision through vision therapy. This is no easy accomplishment. It may require not only optical corrections (proper lenses or prisms and so forth) but very intensive training and learning—in effect, one must learn how to align the eyes and fuse their images, while unlearning the unconscious habit of suppressing vision, which has been occurring perhaps for decades. In this way, vision therapy is directed at the whole person: it requires high motivation and self-awareness, as well as enormous perseverance, practice, and determination, as does psychotherapy, for instance, or learning to play the piano. But it is also highly rewarding, as Sue brings out. And this ability to acquire new perceptual abilities later in life has great implications for anyone interested in neuroscience or rehabilitation and, of course, for the millions of people who, like Sue, have been strabismic since infancy. Sue’s case, together with many others, suggests that if there are even small islands of function in the visual cortex, there may be a fair chance of reactivating and expanding them in later life, even after a lapse of decades, if vision can be made optically possible. Cases like these may offer new hope for those once considered incorrigibly stereoblind. Fixing My Gaze will offer inspiration for anyone in this situation, but it is equally a very remarkable exploration of the brain’s ability to change and adapt, as well as an ode to the fascination and wonder of the visual world, even those parts of it which many of us take for granted.