I myself was born without a left ear, thanks to a rare congenital condition called microtia that afflicts 1 out of every 8,000 infants. No one knows what causes it. My left ear canal's been scarred shut for as long as I can remember; this can often make it very difficult for me to hear people if they're not talking either in front of me or to the right of me. I once got a prosthetic outer ear when I was a kid, so I could wear it and not have to deal so often with the (honestly, genuinely curious) questions of "What happened to your ear?"
Of course, my condition doesn't affect both my ears, and I'm not totally deaf. God willing, I might even be able to get that old ear canal opened up one day. However, having microtia does make it easier for me to sympathize with others who have physical handicaps. It's definitely a cross that I have to bear, but I don't complain. I'm able to succeed in spite of it. I'm the first person on either side of my family to graduate Magna Cum Laude, I'm half-fluent in German, and I'm working on studying Russian as well.
I also remember my health teacher in middle school telling us about a student he once had, who was either born without hands, or lost them due to an accident. Despite this handicap, he still did well in school; he was able to write with his mouth (and, as he told us, his writing was neater than a lot of students' handwriting!) He also told us of a girl who had no eyes in her eye sockets, but whose eyes had grown on her cheeks instead, and whose mouth was shaped like a fish's. She also did very well in school and even made friends, despite her birth conditions.
My point in all these personal stories and anecdotes is, having a physical handicap or birth defect doesn't necessarily make us suffer. We're still able to succeed and live enriching, meaningful lives, despite whatever issues we may have. Our handicaps don't have to limit our choices in what we want to do. And those millions of blind children will often prove to be sources of comfort, support and compassion for each other, for their "normal" families and their "normal" friends.