Fixing My Gaze

A neurologist friend of mine recently told me the following tale. A retired professor came to his office and said, "I think I have had a stroke." My friend asked what his grounds were for saying so, and the professor replied, "I have begun to see phantom figures repeatedly rising out of the floor to my left. Something must have happened in the occipital lobe of my brain on the right side." Sure enough, a scan revealed a small blood clot in the very region of the brain that processes left visual field information.

The professor?s phantoms vanished after a couple of weeks as the clot dissipated. It is interesting to speculate what, in an earlier age, such visions might have prompted: what cathedrals, what wars, what reports from beyond. But to a mind prepared and informed, the upwardly floating spirits immediately implied something much more sensible, not to say more interesting.

A prepared and informed mind, plus a wealth of relevant experience, is what Susan Barry brings to thinking about the fascinating matter of vision. Her account turns on personal experience; she was cross-eyed as a child, and although she had corrective surgery it came too late for her to develop stereoscopic vision.

"Stereoblindness," the lack of ability to see the world in 3D, is the standard accompaniment of strabismus, the condition of having eyes that do not co-operate in focusing so that the images of objects in the world fall in the same place on each retina. It used to be thought that if stereopsis did not develop in childhood it would never develop. Barry, a neurobiologist and professor who lectures on the neurology of vision, discovered otherwise. And in the process she discovered much else.

Barry?s chief discovery was what the world looks like with stereoscopic vision, because against all received wisdom on the matter, and against all expectation, she gained it after optometric therapy based on the work of Frederick W. Brock. Her experience of gaining stereopsis is vividly described.

She sought the help of an optometrist because, as often happens with people who have been cross-eyed in childhood, she had begun in middle age to have other eye alignment problems. After one of many sessions with her optometrist she got into her car and, as she put the key in the ignition, glanced at the steering wheel: and had a sudden epiphanic experience. "It was an ordinary steering wheel against an ordinary dashboard, but it took on a whole new dimension that day. The steering wheel was floating in its own space, with a palpable volume of empty space between the wheel and the dashboard. Curious and excited, I closed one eye and the position of the steering wheel looked ?normal? again; that is, it lay flat just in front of the dashboard. I reopened the closed eye, and the steering wheel floated before me again."

It took longer for Barry?s vision to become fully stereoscopic; many more eye exercises, much dedication, and yet more discoveries about the wonders of the world seen stereoscopically. Barry?s descriptions of walking through falling snow, or standing in a wood and marveling at the depth of space between the trees, are striking: if we have normal sight we so comprehensively forget the familiar that when we hear someone like Barry, newly emerged from a Plato?s Cave of stereoblindness, hymning the way things stand in space, it is as if we see them in space for the first time too.

But Barry learned much more than how to see in stereoscope. She learned that even small misalignments of eyes which, conventionally tested, seem normal, can interfere severely with a child?s education; she cites cases of children whose experience of school was transformed by correct diagnosis of vision problems. She learned that people compensate for the various deficits that accompany stereoblindness by utilizing other capacities, such a bodily movement and touch. She discovered, for example, that she could find her way around in the dark much better than other people, because she registered distances and the disposition of objects by subconsciously making a map of them in the form of her bodily movements among them.

Most important of all, her experience constitutes additional evidence of the plasticity of the brain throughout life. Received wisdom says that the relevant visual pathways are fixed by age eight; she was nearly fifty when she became able to see stereoscopically. This is a remarkable and optimistic fact.

As a result of her own experience Barry began to seek out others who had likewise gained stereopsis in adulthood, and found a number of them, with whom she pooled data. In every case the experience of gaining depth vision was explained in the same amazed terms. One correspondent said that instead of feeling as if she was observing a flat world from a distance, "It feels like I am in the world. Empty space looks and feels palpable, tangible ? alive!" Barry agrees: the experience is one of a "powerful sense of immersion?my whole sense of space had changed."

Along the thread of the narrative of how she gained stereopsis Barry strings a lucid account of the eyes and their functioning, what strabismus and stereoblindness is, how normal stereoscopic vision works, and how therapeutic optometry can correct or alleviate problems of vision. She is an excellent guide not only to these topics, but to the unexpected further difficulties that vision problems cause. Normally sighted people are apt to think that the only vision problem worth mentioning is blindness. In fact there are many forms of visual deficit, even with people who -- like Barry herself -- have perfect 20/20 vision in each eye separately when conventionally tested. Problems arise when the alignment of the eyes is not right; to recur to the all-important point about children with undetected eye problems, even the subtlest misalignment can manifest as lack of attention at school, difficulties with perceiving numbers or letters, withdrawal and moodiness, clumsiness at ball games, general under- performance -- all of these symptoms feed upon and exacerbate each other, and anxious parents often never discover that their child?s problems can be corrected with vision treatment. This is something eminently worth knowing.

It is hard to imagine the dramatic nature of the sudden epiphany that stereoblind people have if they gain stereopsis, as when Barry saw the steering wheel floating before her. Stereoblind people perceive the world in two dimensions, as a flat display; they judge distance and depth by such cues as size, shading, and the partial obscuring of one object by another. They have to develop these techniques in childhood because they suppress the information coming from one of their eyes, since the data from both eyes fail to match. Nothing in the experience of the stereoblind, Barry tells us, can prepare them for what stereoscopic vision is like. If they get it, the experience can be overwhelming; it can even cause vertigo, as happened to Barry, and sensations of travel-sickness.

Indeed it alters things more dramatically still. "Most surprising to me was that the change in my vision affected the way that I thought," Barry writes. "I had always seen and reasoned in a step-by-step manner?My son and daughter, when young, could grasp details and the big picture at the same time. I didn?t know how to do this until midlife."

This book could change other people?s lives likewise. It will surely persuade people with eye alignment problems to seek optometric therapy. It will surely alert some parents of underperforming or difficult children to a possible source of their problems. With the added evidence it offers of the brain?s perennial plasticity, this book will encourage us all because it suggests that if people can reconstruct pathways of vision, there are other things they might succeed in doing. It is a pleasant and optimistic thought indeed, that at any point in life we might, if determined enough, be able to fix things, improve, mend, and grow in positive ways: even to see more clearly, and not just with our eyes.

About the Columnist
A. C. Grayling is an author, playwright, reviewer, cultural journalist, and professor of philosophy at London University. The most recent of his many books are Towards the Light of Liberty and The Choice of Hercules. His play Grace was recently performed in New York City.

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