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Virtual Reality

Do you see with your eyes? I'll bet you find this question strange and the answer obvious. You're likely thinking, Of course I do. You're wrong. Here's another odd question: What happens when you open your eyes? When you open your eyes you see the world around you, right? There's not much more to say about it, is there? Now you're very wrong. (If you're thinking, This blind guy is crazy and I should stop reading his book, stay with me for another few pages, please!)

As a kid growing up in Miami, I would have given the same wrong answers to these two questions. I can picture myself at the age of thirteen acting on the set of a television commercial at Filmworks, attending one of my dad's many hearings in the Miami-Dade County Courthouse, or taking classes in the theater program at New World School of the Arts. I took my sight for granted, as most people do. It was not something I thought about. I saw just fine. I didn't even need glasses like the youngest of my older sisters, Ronit (pronounced "row," as you would a canoe, and "neat," as in "interesting").

That thirteen-year-old Isaac would answer our two questions impatiently and confidently, saying something like: "Yes, of course I see with my eyes. When I open my eyes I see what they are pointed at. I'm walking away now, sorry." Young Isaac was invincible. He did not know he had a disease called retinitis pigmentosa, or RP, that would dramatically change his answers to these questions as he slowly went blind. But I did have RP, I did go blind, and my answers did change.

To understand how, imagine the "Magic TV," the huge screen above center court at Orlando's Amway Center, where the Orlando Magic play. It's forty-two feet tall and forty-two feet wide, for a total area of 1,764 square feet. It has 9,470,400 pixels that collectively create the images you see, just like the pixels on your computer monitor.

The retina at the back of each of your eyes is like that Magic TV. It is a little smaller, approximately one thousand square millimeters, and it has a bit more pixels, approximately 125 million on each retina. (Put another way, the average human retina has 13.2 times more "pixels" than Amway's screen, even though that giant screen is 163,881 times bigger.) In terms of resolution, the retina is 2,163,068 times more powerful.

Instead of LED bulbs, the "pixels" of the retina are special cells called photoreceptor cells. They come in two varieties, known as "rods" and "cones" for their respective shapes. Just as the bulbs on the Jumbotron screen individually turn on or off to create an image in aggregate, each photoreceptor cell captures information about its tiny piece of the world. Each rod or cone cell is tuned to particular wavelengths, or colors, of light. (The more numerous rods respond to light of any color, while the cones, which are concentrated toward the center of the eye, each respond only to a particular color.) When a photoreceptor cell is hit by light that it is tuned to receive, it "fires," producing a bit of biological magic, a chemical reaction that generates a signal sent back to your brain. When you open your eyes, your 250 million photoreceptor cells fire feverishly to create your image of the world.

RP causes the photoreceptor cells to deteriorate, cease to function and ultimately die. Returning to the Magic TV, imagine that you are watching my life as a movie on that giant screen. Imagine further that the pixels on that screen slowly and randomly break. At first, you might not even notice, but as more and more pixels break you will start to spot holes in the image, dark regions on the screen. Over time those regions will grow in size and number. As still more pixels break, you will eventually struggle to decipher what you are watching. That struggle will grow more difficult and less successful as more pixels break. You will see less and less of my life as the movie plays on, until finally you'll see nothing at all.

That is what my sight was like as RP progressively broke the photoreceptor cells of my retina. It is impossible to say exactly when the deterioration of my sight started, and it is impossible to pinpoint a precise moment in time when I became blind as a result. I know, however, that as a young child I grew up with seemingly normal sight, through my teens my sight was clearly failing, and by my early twenties my dwindling sight was of diminishing use to me. I lived as a blind man by my twenty-fifth birthday.

One pleasant Saturday in the spring of 1997, I was walking through Harvard Square in Cambridge, Massachusetts, on my way to buy a late lunch. I was seventeen years old, a sophomore studying mathematics and computer science at Harvard College. My late lunch was technically a very late breakfast, as I had managed to roust myself from my bed only an hour earlier. The plan for breakfast was a cheeseburger sub from Pinocchio's Pizza & Subs on Winthrop Street—or "Nokes," as we called it. The plan was making my mouth water with eager anticipation.

I turned a corner and a giant tree branch came flying at my head. Luckily, I reacted quickly, diving to the side, landing in some bushes. Major, perhaps life-threatening head trauma was narrowly avoided, and I sustained only a few minor scrapes and bruises. I stood up, brushed off dirt and leaves, and heartily congratulated myself for preventing major injury with my impressive catlike speed and reflexes.

Then I looked around and realized the self-congratulation was unwarranted. There was no flying branch. There was a giant tree branch suspended over the sidewalk, well above my head, but it was firmly affixed to a towering tree. Neither the tree nor its branch had budged recently.

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