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Coming to Our Senses
A Boy Who Learned to See, a Girl Who Learned to Hear, and How We All Discover the World
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We think of perception as a passive, mechanical process, as if our eyes are cameras and our ears microphones. But as neurobiologist Susan R. Barry argues, perception is a deeply personal act. Our environments, our relationships, and our actions shape and reshape our senses throughout our lives.
This idea is no more apparent than in the cases of people who gain senses as adults. Barry tells the stories of Liam McCoy, practically blind from birth, and Zohra Damji, born deaf, in the decade following surgeries that restored their senses. As Liam and Zohra learned entirely new ways of being, Barry discovered an entirely new model of the nature of perception. Coming to Our Senses is a celebration of human resilience and a powerful reminder that, before you can really understand other people, you must first recognize that their worlds are fundamentally different from your own.
To give back his sight to a congenitally blind patient is more the work of an educationist than that of a surgeon.
—F. MOREAU, quoted in M. von Senden, Space and Sight: The Perception of Space and Shape in the Congenitally Blind Before and After Operation (Glencoe, IL: Free Press, 1960), 160.
– chapter 1 –
How Far Is Your Vision?
IN THE OPENING SCENE OF A BEST-SELLING NOVEL, THE CURATOR of a famous museum is shot and killed. His murderer, we later learn, is a white-haired man with albinism. For my friend, Liam McCoy, the selection of the murderer makes no sense. Liam has albinism and knows that most people with his condition could not have carried out the murder. Their vision is just too poor.
I first met Liam through his ophthalmologist, Dr. R. Lawrence Tychsen, who had invited me to give a talk to the Department of Ophthalmology at Washington University in St. Louis. Dr. T. (as Liam calls him) treats children with neurological impairments, often so severe that other doctors consider them too difficult to examine and treat. He was intrigued by my story of gaining stereovision as an adult and then told me about one of his patients with a remarkable vision-recovery story. “You must meet Liam,” he said to me, and so, over many phone calls, emails, and visits, Liam told me his story.
IT WAS OBVIOUS TO THE OBSTETRICS NURSE THAT SOMETHING WAS different about Liam the moment his head crowned. Liam’s hair was metallic silver, and blood vessels were plainly visible through his very light-colored skin. “Oh my God!” the nurse exclaimed as she rushed from the delivery room. Moments later, she returned with the doctor, who took one look at the newborn and hurried out too. When the doctor returned, Cindy, Liam’s mom, now deeply concerned, asked what was wrong. “Oh, he’s a towhead; he’s a cotton-top,” the doctor responded. But it would have been better had the doctor not been quoted the next day in the hospital newsletter as saying, “I’ve never seen a baby with such silver blonde hair!” Strangers kept stopping into the hospital room to peek at the new baby. Cindy took Liam home as soon as possible, just to get some rest.
Liam had a mohawk of silver hair running from the back to the front of his head. But when Cindy tried to take pictures of the silver strands, all the photos came out overexposed. Her baby’s hair was just too pale to show up well in pictures. From the start, Cindy suspected that her child had albinism. She had known several people with this condition. By coincidence, at her previous workplace, the cafeteria had been staffed (cooks, waiters, and waitresses) entirely by people with albinism. So when Liam was just one week old, Cindy asked the pediatrician about her concerns. The pediatrician dismissed them. Liam’s eyes were a pale blue. He had Nordic relatives on his father’s side so, the doctor thought, he might favor them. In retrospect, his misdiagnosis is not surprising. Albinism, or a lack of pigment in the hair, eyes, and skin, is a rare condition, affecting only one in seventeen thousand people. And in contrast to incorrect and often cruel media portrayals, people with albinism do not have pink or red eyes. Like Liam, their eyes are blue, gray, or sometimes violet. So, it was not until Liam was seventeen months old that a genetics specialist confirmed that he had albinism.
Liam’s blue eyes result from a lack of the pigment, melanin, in the iris, the colored part of the eye that controls the size and diameter of the pupil. While melanin makes our eyes green or brown, there are no pigments that make our eyes blue. The iris is made up of several tissue layers, and the blueness results from the way light is scattered by these layers. (A similar phenomenon makes the sky blue.) Not just individuals with albinism but all people with blue eyes lack melanin in the front of the iris. What distinguishes people with albinism from others with blue eyes is that they have little or no melanin in other parts of the iris and eye and, in many cases, in the skin and hair as well. Indeed, several gene mutations have now been discovered that result in albinism, and all of these mutations affect the synthesis of melanin throughout the body.
Many people think of people with albinism as pigmentless. But this is not the case. Melanin is only one class of the many pigments found in our bodies. Other pigments include hemoglobin, the oxygen-binding molecule in our blood, as well as rhodopsin and photopsin, the light-sensing pigments found in the rod and cone cells of our eyes. People with albinism have these other pigments; only melanin is reduced or lacking.
It must have been lonely for Cindy as a new mother. She could not take her baby for walks or to the park on a bright, sunny day. Like many babies with albinism, Liam was photophobic, extremely sensitive to bright light. Here, too, the lack of melanin is to blame. Melanin is found not only in the front of the iris but also in the back, where it prevents light from entering the eye. Because of melanin, light enters our eye through only one point, the pupil. In bright sunshine, we contract our pupil to reduce the amount of light that hits the retina, while, in the dark, we dilate our pupils to allow in more light. Without melanin in the back of the iris, people with albinism have a harder time regulating how much light enters the eye, and the extra light causes painful glare. So Cindy took Liam out only at night or at dawn or dusk. She put up special utility lights around her house for watching Liam after sunset and got the neighbor’s permission to put Liam’s toddler pool by their wall in the shade between the two houses.
When Liam was four months old, Cindy grew increasingly concerned about his vision. She had just started feeding him solid food. She would fill the spoon and then move it back and forth slowly in front of him. Even though Liam was hungry, he did not follow the spoon’s movements with his eyes. So Cindy took Liam to the pediatrician and asked about his vision. The doctor walked around the room with a flashlight in order to see if Liam followed the light with his eyes. The doctor claimed that he could see just fine.
But Cindy had been trained as a speech pathologist working with blind and deaf children. She was not confident in the doctor’s conclusions. To stimulate Liam’s vision, Cindy clamped a light onto the changing table and kept it on at all times to give Liam something to see and orient to. She taped a Dairy Queen ad, full of red and black colors, to Liam’s crib. She also noticed that Liam’s eyes wandered, and this eye misalignment, or strabismus, did not improve with age. When Liam was old enough to stand and talk to his mom, his right eye would move up and out so that it seemed to Cindy that Liam was looking over her left shoulder. Liam remembers his eyes as uncontrollable. Like most people with albinism, he had nystagmus, an involuntary oscillating movement of the eyes. He could not willingly look at anything.
Despite problems with his vision, Liam developed motor skills faster than most babies. One moment, he managed to get up on all fours, and the next moment he was crawling. His balance was excellent. Once Cindy snapped a photo of Liam balancing on a moving rocking chair before ordering him to get down. Liam began to walk quite early, at seven to nine months, but he grabbed hard onto Cindy’s fingers when he walked and would not let go. He needed Cindy for visual guidance, not balance. Up and down their home they marched until one day, when Liam was just over a year old, he saw a bright reflection on a filing cabinet two or three feet away. At that moment, Cindy was across the room folding clothes, but she spied Liam as he let go of a laundry hamper and walked off independently, without even a wobble, to the shiny cabinet to investigate. Liam’s motor skills and liveliness remind me of the young Helen Keller as described by her teacher, Anne Sullivan.1 Though Keller was blind and deaf, she spent her days running, jumping, spinning, swimming, and even climbing trees. She was, according to Sullivan, “graceful as a nymph.”
At sixteen or seventeen months old, Liam developed a rash. Cindy took him to the pediatrician’s office, but their normal doctor wasn’t in, so they saw his partner instead. “Whom does he see for his eyes?” asked this doctor immediately upon entering the room. In contrast to their normal pediatrician, he noticed immediately that Liam’s eyes didn’t work together. Finally, Cindy had confirmation that something was wrong with Liam’s vision. The doctor referred them to a pediatric ophthalmologist, whom they went to see soon afterward. But this visit proved disastrous. He examined Liam and abruptly announced, “He’s blind, and there’s nothing we can do about it. He can see the big E and that’s all he’ll ever see.”
Later that same day, Cindy went shopping and took Liam with her. It was almost Christmastime. Cindy picked out some toys and hid them under other items in her shopping cart. When the cashier started to ring up a toy, Liam asked if it was for him. “Blind? My foot!” Cindy thought.
OUR EYES ARE NOT FULLY FORMED AT BIRTH. INDEED, THEY MAY continue to develop up to age eight, and our vision takes even longer to mature.2 If a baby could read, he still couldn’t see and identify the letters on the standard Snellen eye chart some twenty feet away. A newborn’s visual acuity is much poorer than that of an adult. People with albinism have vision that, in many ways, resembles that of a newborn baby. Even with glasses, their acuity, as measured using an eye chart, does not reach the normal 20/20 and may fall in the 20/40 to 20/200 range. A person with 20/40 vision sees at twenty feet what a person with 20/20 acuity can see at forty feet while a person with 20/200 acuity sees at twenty feet what a person with 20/20 vision can see as far away as two hundred feet. Given such poor sight, a person with 20/200 acuity is considered legally blind.
Anyone first studying the human eye may be surprised by the way its structures are arranged. The anatomy seems backward. Our retina, the light-sensing part of the eye, isn’t located toward the front of the eye, where light enters, but is found in the back of the eyeball instead. What’s more, the retina contains several layers of cells and neuronal processes, and the light-sensing cells, the rods and cones, are located in the layers almost furthest back. Rod cells are important for vision in low light and cone cells for color vision. These cells contain the light-absorbing compounds photopsin and rhodopsin, which are present in people with albinism. So, photons of light must pass through numerous structures and cells after entering the eye and retina before being absorbed by the light-sensing pigments in the rods and cones. This arrangement works because most of the eye’s internal structures are transparent to light. However, as the baby grows, several changes occur in the retina that allow for high-acuity adult vision.
In the months after birth, the central part of the retina folds inward toward the back of the eye in the shape of a pit. This increases its surface area, allowing for the accumulation of more light-sensing cone cells. Indeed this change in shape has given the central retinal region its name, the fovea, which is the Latin word for “pit.” Only cone cells are found in the fovea, although both rod and cone cells are found outside this region. As the retina matures, more and more cone cells migrate into the foveal region from the retinal periphery so that cone cells end up more tightly packed in the fovea than anywhere else in the retina. The outer segment of cones, the part of the cell that contains photopsin, also grows longer in foveal cones than elsewhere in the retina. What’s more, all the other overlying retinal cells and processes move away from the front of the foveal pit. In this way, light hitting the retina at the fovea is transmitted directly to the cones without having to pass through other cell layers.3
It is not surprising then that we aim our eyes directly at an object to see it most clearly. When we look directly at a target, its image is cast on our foveas, which provide us with our sharpest vision. To appreciate the acuity of your foveal vision, try reading these words while looking straight ahead but holding the book a little to your right or left. In this way, you are looking at the letters, not with the fovea, but with more peripheral parts of your retina. You can see the letters; they are not exactly blurry, but they are not well resolved. You would have to increase the font size of the letters to read them.
But the fovea doesn’t develop normally in people with albinism, like Liam, and, again, the absence of melanin is to blame. This pigment is found not only in the iris but in the retinal pigment epithelium, a sheet of tissue at the very back of the retina that envelops and nourishes the rods and cones. These epithelial cells are chock-full of melanin granules. As in other pigmented parts of the body, cells in the retinal pigment epithelium make their own melanin from the amino acid tyrosine in a series of chemical steps. Tyrosine is first converted into a compound called DOPA and then into several other molecules before its final conversion to melanin, and this pathway is deficient in many forms of albinism. As the retina develops, DOPA and melanin may be very important for the formation of the foveal pit and the migration of retinal cells.4 Without these compounds, the foveal pit does not form normally, fewer cone cells move into the fovea, and fewer rod cells are found in other parts of the retina. So the retina in a person with albinism, with a shallow or nonexistent foveal pit and more loosely packed cones, resembles that of a newborn infant.5 Without a well-formed fovea, visual acuity is compromised in a way that glasses cannot correct.
LIAM USED WHAT VISION HE HAD. TO INSPECT A NEW TOY, HE would bring it close to his face, so close that it was almost touching the corner of his right eye where he could see objects best. He would examine the toy thoroughly at this close range, going over every detail. Later, when he played with it, he did not try to see it but relied on his memory of it instead. Every time Cindy moved a toy to a new spot, Liam watched closely and then memorized exactly where that toy had been placed. I have yet to meet a person with significant vision problems or blindness who does not have an exceptional memory. Liam’s memory was honed from an early age.6
Still, Cindy needed to know just how much Liam could see. One day, when Liam was two, Cindy quietly slipped into her bedroom. Shortly afterward, Liam started looking for her, going methodically from room to room, guiding his movements more by memory and touch than vision. He would enter each room and call, “Mommy,” but Cindy didn’t answer. When Liam got to Cindy’s bedroom, he came right up to her and asked, “Mommy?” Cindy still said nothing, and Liam turned away, continuing his search. When Liam finally came back to the bedroom and called again, Cindy answered. She has never forgotten this incident. It tortured her then and still pains her now to have not answered when Liam called, but she had to find out just how well he could see.
Between the ages of seventeen and thirty-four months, Liam saw the pediatric ophthalmologist four times. He hated the doctor. Imagine how painful it must have been for him during exams to have a bright light directed into his eyes. On the second or third visit, upon Cindy’s insistence that the doctor address Liam’s strabismus, the ophthalmologist patched one of Liam’s eyes and left the room. Liam sat quietly in Cindy’s lap, without reaching up to fuss with the patch. Then the doctor returned, and the sight of him so frightened Liam that he instantly burst into tears. The doctor ripped off the patch and told Cindy that, given Liam’s poor vision, patching or any other treatment for strabismus would not work anyway. That was the end of that.
With strabismus, the two eyes are not looking at the same place in space so they provide conflicting input to the brain. A person with strabismus might adjust by squinting one eye shut. Some of my baby pictures show me dealing with my strabismus in this way. When my father’s left eye crossed in his eighties, he’d look at me with his right eye wide open and his left eye almost shut. So, it’s not surprising that in Britain strabismus is called by the unflattering name “squint.” Liam too had to adjust to his misaligned eyes, which he did by habitually closing his right eye, thus looking almost exclusively with his left. To see anything out of the right eye, Liam had to close his left eye completely and then raise his right brow hard to move the right eyelid out of the way.
But why would a person with albinism develop strabismus, or misaligned eyes? While strabismus is found in about 4 percent of the general population, it is much more common in people with albinism. Strabismus may develop for a different reason in people with albinism because of a difference in the way the eyes are wired to the brain.
When you reach for a cup with your right hand, neurons on the left side of the brain fire to initiate and direct the movement. When your right hand contacts the cup, sensory signals are sent back to the left side of the brain. Tap your left foot, and neurons in your right brain are active. So, motor control and sensory processing for one side of the body occur in the opposite (contralateral) side of the brain. By analogy with your limbs, you might think that information from the right eye will be processed by the left brain and vice versa. That is indeed the case for animals, like rabbits, with laterally placed eyes. But it’s not true for animals, like ourselves, whose eyes face forward.
Since our eyes are located on the front, not the sides of our face, each eye sees both the right and left halves of the visual field. Look out of either eye alone, and you’ll see what I mean. So, it wouldn’t make sense for input from the two eyes to be processed separately by opposite sides of the brain. Instead, visual information from the left side of the visual field is processed by the right half of the brain, and information from the right visual field is processed by the left. Imagine light rays traveling toward you, perhaps reflected by a bright object off to your left. These rays travel in a straight line, hitting the right, not the left, sides of both your forward-facing retinas. So, light emanating from the left visual field hits the right side of both retinas and is processed by the right side of the brain. The reverse is true for light coming from the right. As a result, input about a single object, as seen by both eyes, converges on the same neurons in the visual parts of the brain.
How, then, are our eyes wired to the brain to allow for this arrangement? Nerve fibers leave the retina in the optic nerve and pass through a brain region called the optic chiasm on their way to other visual areas. At the optic chiasm, there is a partial crossing over (partial decussation) of nerve fibers traveling from the retina to the rest of the brain.7 Input coming from the right visual field excites the left retina of the left eye and is sent to the left side of the brain without crossing at the optic chiasm. But this same input also excites the left retina of the right eye and must cross over at the optic chiasm to the left brain to merge with the input from the left eye. The reverse is true for visual stimuli coming from the left visual field. So, in people with normal vision, about half the fibers coming from each eye cross to the other side of the brain at the optic chiasm.
However, the retinal nerve fibers don’t follow these paths in a person with albinism. Some fibers that should stay on the same side of the brain cross over instead, and the extent of aberrant crossing over may vary from person to person.8 This means that visual information from part of the right visual field goes to both the left and right sides of the brain. The same is true for input from the left visual field. This misrouting is correlated with the lack of pigment in albinism and may lead, in turn, to disturbances in eye-movement control, causing misaligned eyes and an inability to see in 3D.9 Testing, done when Liam was older, showed that he had excessive crossing over, and this may have contributed to his strabismus.
But we have to be careful in using our incomplete knowledge of vision and visual development to predict what someone can see. People with albinism don’t have trouble, for example, seeing on which side of the visual field an object is located. Some people with albinism and the eye-brain misrouting have straight eyes and some degree of stereovision, and they are able to use their stereovision to judge depth and size.10
TWO YEARS AFTER LIAM WAS BORN, CINDY HAD A SECOND CHILD, a little boy who suffered from different but difficult medical complications. His pediatrician recommended that they see a specialist, not in their hometown of Columbia, Missouri, but at Children’s Hospital in St. Louis. So Cindy asked if the doctor knew of a good pediatric ophthalmologist there. “As a matter of fact, I do,” said the doctor, who then went off to his office to arrange appointments with both doctors on the same day.
It was a long, exhausting day in April when Liam and Cindy first met Dr. Tychsen. The morning was taken up with testing and consultations for Liam’s brother. When they finally got to the ophthalmology offices in the afternoon, the receptionist took one look at Liam and asked about his glasses. Cindy told her that Liam didn’t have glasses, and the receptionist looked surprised, commenting that children like Liam often have glasses by his age. Even the receptionist, Cindy thought, knew that Liam should have had treatment by this time. Then Liam went through a host of vision tests before they met Dr. Tychsen. Through it all, Cindy worried what the backlash from this long afternoon would be. After each of their four visits to the previous ophthalmologist, Liam had withdrawn completely, not speaking to anyone but his mother for two weeks. Yet the contrast between the two doctors could not have been greater. Dr. Tychsen was a quiet presence. He never rushed them, and he never insisted. As they left his office, Liam asked, “Mommy, can we come back tomorrow and see Dr. T, the doctor who loves me?”
Dr. Tychsen explained that Liam was living in “a cocoon of visual blur.” His zone of clear vision extended out only three inches from his nose. Liam’s visual impairments were a mixture of three disorders: extreme nearsightedness (pathological myopia), strabismus (eye misalignment causing double vision, lack of depth perception, and visual confusion), and albinism. The myopia was treated by prescribing thick glasses, which improved Liam’s distance vision from 20/2000 to 20/200. Dr Tychsen addressed Liam’s strabismus by performing a sequence of eye-muscle surgeries at ages three, five, and seven. After the first surgery and, indeed, after every intervention in Liam’s vision, Cindy, a most wise, observant, and devoted mother, was repeatedly taken aback by Liam’s reactions. These were often revealed by a casual remark that Liam would drop here and there. After the first strabismic surgery, Liam asked, “What did you do with my other mommy—the fun one who stood behind you?” Before surgery, Liam had double vision. He saw the second mommy image above the first, and it appeared to walk on tables and play in the air.
Liam was not entirely blind, but his visual development had been severely disrupted. Even with his glasses, he couldn’t see faces or objects a few feet away or understand spatial layout. Thirteen years after Liam’s first visit, Dr. Tychsen, through a new series of operations, was able to give Liam near-normal eyesight. Yet Liam’s lack of visual experience throughout childhood had a long-lasting impact. As we shall see, the operations were only the beginning of Liam’s vision restoration.
AS A CHILD, LIAM COULDN’T DISTINGUISH A CAT FROM A DOG. Each was, as Liam later wrote to me, “a living thing that was on the ground and had hair.” When Liam looked at someone’s face, the mouth and nose blended together into one big blur. Eyes were two dark spots. So Liam didn’t learn to recognize faces or facial expressions. He identified people by their hairline, skin color, and clothes, and this placed severe restrictions on what Cindy could wear. One morning Cindy shed her usual dark blouse and pants and dressed up in a skirt and boots to give a speech at church. When she came down to the kitchen, Liam got very upset and demanded to know what had happened to his mother. Cindy assured him that everything would be all right and kept the nice clothes on, just this one time, for church. During one of their trips to the medical center in Columbia, Liam, mistaking a strange lady in dark clothes for his mother, followed her into an elevator. After a few panicked moments, Cindy found Liam with a security officer in the elevator lobby on another floor. From that day onward, Liam always grabbed his mother’s and his brother’s hands before entering an elevator, insisting, as the protective older sibling, that they must all hold hands lest his brother get separated from them. Given Liam’s limited vision, Cindy knew better than to ever try to wear a hat.
But poor vision did not prevent Liam from learning to ride a bike. When Liam was five and a half, a kid-sized bike showed up for Christmas. It was a mystery gift, and, to this day, neither Cindy nor Liam knows who gave it to him. The shiny new bike was big for Liam, but he learned to ride it anyway in a nearby parking lot, even sliding down the December snow banks the way other kids did.
One day at about this time, Cindy took Liam out of the car, put him down at its back, and walked toward the front. Liam froze. He could no longer see Cindy. His bubble of vision allowed him to see clear images only very close up and to make out blurry images no further than four feet away. Cindy wondered what would happen when Liam grew to be more than four feet tall and could no longer see the ground from his bike. Sure enough, he stopped riding.
- On Sale
- Jun 8, 2021
- Page Count
- 272 pages
- Basic Books