Translator: Robert Tucker
Reviewer: Tanya Cushman I would like to begin today by asking you all
to close one of your eyes. Raise your arms out in front of you and try to touch
your two index fingers together. This is going to look something like this. As many people notice,
this is not really an easy task. What you're experiencing is a lack of depth perception
as a result of closing one of your eyes. Well, this is how I live my daily life. My name is Katarina Stephan, and I have one eye. If you knew me in middle school, you may know me
by my nickname: Three Eyes. You can do the math. The name comes from the humor
of my clever classmates in which needing glasses to see
but only having one eye justified my name, Three Eyes. I was born with a rare congenital anomaly
that left me virtually blind at birth. At eight, my left eye
was surgically removed. At nine, I begun wearing
a prosthetic left eye. At 12, I met my ballet coach,
Whatmora Casey. He transformed my handicap
into a strength. At 18, I trained with a professional
ballet company in Austria. At 19, I taught cardiothoracic surgery and assisted in human heart
procurements for transplants. Today, at 20, I stand before you to tell you a story of darkness and light,
of physical eyesight and vision. My life demonstrates
that living with one eye can be very similar to your life with two, and that the information
that I have learned along the way to compensate for my vision loss is translatable to your life. Mental visualization, proprioception,
and motion parallax, are three nuances that exist and demonstrate
the power of our bodies and minds. First, let me clarify what vision is not. Our purely physical eyesight,
which we rely on above all other senses, does not always provide
an accurate picture of our world. To demonstrate this,
I am going to need your help. In this optical illusion, how many of you see the female dancer
in the center rotating clockwise? How many of you see her
rotating counterclockwise? As you can tell, we do not all agree. In the center image,
there is a lack of visual depth cues which is causing our brains
to interpret the image differently. Our eyes are therefore not responsible for everything that we are
visually experiencing. In dreams, for example, our brains
can generate a visual experience without any sensory input from our eyes. Likewise, if I asked you
to visualize what a glass car looks like, you would have no problem visualizing one,
although you have never actually seen one. Vision involves a construction
of a mental image of our external world. Our purely physical eyesight
is not as reliable as we assume. But our internal vision,
generated in our mind, compensates for the illusion
of pure physical eyesight. The exercise of mentally
visualizing a glass car serves as a brief introduction
to the mental visualization that has served as my internal guide. When training for my ballet career, I had to learn to compensate
for not having two eyes. In order to achieve the impeccable balance
needed on pointe shoes, I learned to close my eyes as I danced. I created a mental representation
of each movement, as if I were truly performing
in a virtual body in my mind. In doing so, I was able to achieve
that balance in my virtual body and translate that information
to my physical body in space. However, I did not only
see these corrections; I felt them too. At 16, I contracted a near-fatal infection
that left me in a wheelchair for months. Doctors told me I would never dance again. So, I danced with the virtual body
in my mind instead. I visualized and mentally felt
every muscle activation required to perform with the virtual
body in my mind. In doing so, I never really
stopped dancing. I did what astronauts do
when training in zero-gravity conditions to prevent muscle atrophy. My mind activated my muscles. One year later, I returned to ballet
after a remarkably fast recovery, proved my doctors wrong, and performed with a professional
ballet company in Austria. I succeeded as a ballerina because of my heightened awareness
to mental visualization, but also my awareness
to my proprioception. Proprioception is an awareness
of our bodies in space, an awareness to where each part is
relative to one another. Proprioception is what allows us to move
and react to our external environment without using our eyes. We all use proprioception. For example, close your eyes,
raise your index finger to your nose. If you were able to do so, then you have just located
your nose in space using proprioception. This is a sense that is so informative
that it can serve as a third eye, or, in my case, a second eye. We all have the ability
to strengthen our own proprioception through mind-body exercises. For example, performing daily tasks
with your eyes closed enhances that brain-body communication. My awareness to mental visualization, and my ability to apply this
and proprioception to complex tasks, gave me the second eye
I needed to perform surgery. At Stanford, I was a teaching assistant in a cardiothoracic
surgical simulation lab. I performed surgeries
such as septum defect repairs and coronary artery bypasses. Initially, I was slower than my peers. However, over time I began to memorize
the delicate feel of the body tissue, the weights of the surgical instruments, and the feeling of my hand wielding
the instrument upon the body tissue. In doing so, I was able to keep up. I used my mental visualization to imagine where I should be
within the simulated body cavity and confirmed this
by the feeling that I was having. In doing so, I executed these surgeries
without relying on my vision. I began this talk by asking you all
to close one of your eyes. This was to demonstrate
a lack of depth perception as a result of only having one eye. An individual with two eyes
aligns him or herself in space so that the third dimension can be seen. Each eye is responsible
for generating an image. It is the brain's responsibility
to intercept these images into one, and subsequently create a third dimension. However, in theory, then, an individual with one eye should not
be able to see the third dimension. However, I do so, and I do in two ways. In the first method,
I use time rather than space. This is called motion parallax. My eye captures one image
and engraves it into my mind. Then I move my head ever so slightly to capture a second image
taken a split second apart. In doing so, my brain
can interpret these photos and create the third dimension. We all use motion parallax. In this example, we are able to tell that the pillars are closer
in proximity to us than the brick wall. This is because the pillars are moving at a faster speed
relative to the brick wall. Therefore, we are using time
and motion rather than space to determine depth perception. In the second method that I use
to generate the third dimension, I use my senses, specifically proprioception. It is this sixth sense that gave me the power to perform
both on stage and in the operating room. When I was four, the doctors took
the eyepatch off my single good eye. Lights and color flowed into my life. When doctors told me
I would never dance again, darkness flooded my life. When six months later
my mother passed away, I thought I would never see
the light again. Moving from a wheelchair
to dancing on stage, I began to see the lights again. Moving to Austria to then dance
with the ballet company, only to realize that ballet
is not my true vocation, darkness flooded in again. Finally, when I internalized
the voice of my mother and returned to America
to pursue a career in academia, I attended Columbia University,
now as a student, and I am continuing to chase the light. Today, I continue to chase this light. I am an EMT with Columbia University
Emergency Medical Services, and I drive their ambulance
in New York City with just one eye. I have recently met doctors in Boston
who are engineering visual prostheses that have the capacity
to restore vision to the blind. I will personally assist them this summer, by providing user interface
to the medical devices. I fully intend on chasing light and color
for every blind person in this world. Mental visualization, proprioception,
and motion parallax, are three internal guides that testify
to the power of our bodies and minds. These innate abilities
manifest in other species as well. For example, dogs use their acute sense of smell
to navigate the world, bats use echolocation, and birds can detect
the earth's electromagnetic field. These internal guides
are exceptionally powerful. I urge you not only to become aware
but to utilize them, especially in times of trial. Remember that when life gets difficult,
you have two options: to focus your awareness
on your external or internal vision. Let this internal guide let the light in. Go out into this world,
pay it forward, and chase color. Thank you. (Applause)
