So doctors take a step by step approach, laying the inside membrane, then eventually using a combination of bone and cartilage from the skull or other part of the body for the structure and covering it with skin again.
These surgeries are successful, particularly in children. "They're very healthy, don't smoke or drink and don't have artheroschlerosis," said Tatum. "They have tremendous healing power and are less likely to get infection."
The hardest part for children is the social challenges.
Since the fifth grade, Cassidy has gone to Governor Morehead School. The first week, Cassidy turned to her mother and said, "Mom, everyone here is blind, so I'm normal."
Though she had some stares and taunts as a young child, her social life today is busy. "Honestly, there's been a bit of teasing, but not more than any other child on a regular day," said her mother.
If Hooper is with her daughter and notices stares, she'll often say preemptively, "Do you have a question -- she looks kind of different. And she'll answer the question herself."
"When kids realize it's just an outward thing, and she likes everything else other teenagers like, they are more accepting," she said.
Cassidy is a strong student on the graduation track to go to college and study broadcast journalism.
"She's very outgoing and never met a stranger," said Hooper. "Whenever we go anywhere, she says, 'Put me by the pool and I'll go make friends.' She loves to talk and is very, very self-confident."
In 2011, Cassidy protested a law that required the Department of Public Instruction to close one of three schools that serve the blind and deaf in North Carolina, appearing at a public hearing in Raleigh. Her school was spared.
"I love it," she said. "The class sizes are real small -- 9 or 10 kids -- you might be the only student in the class."
In track and field events, she runs the 75-yard dash with the help of a cable to direct her. "I hold on to this rope and it slides across the cable like a zip line. I just run and it helps me."
When she does curling -- the Canadian Olympic sport on ice -- she relies on an assistant to serve as her eyes.
"To me, if it's something hard, I get through it," said Cassidy.
Her classmate and friend, Noah Cameron Long, 20, is impressed with her spirit and her talent. He, too, has been blind since birth and uses a walker because of cerebral palsy.
"She is very technologically savvy," said Long, who is from Fuquay-Varina, N.C. "We both want to go into the same field in the future."
The couple has dated since 2009 and has done campus radio shows together. "She's really into music," said Long.
Cassidy uses a screen reader program called Jaws for her computers at home and at school. She also has an iPad with a voice over. "Apple makes it more accessible for blind people," she said.
Already, she is a bit of a local celebrity. Cassidy's story is one of several others with challenges in the book by two Charlotte authors, "Forever Hellos, Hard Good-Byes."
Just recently, a local radio host offered her the microphone.
"It was the first time and I actually did my own radio broadcast for an hour -- I took over," she said. "I have been listening to radio since I was younger, and I like how they do it. I am interested in jingles."
Among her guests were the authors of the book. Cassidy's advice to others with disabilities -- "If you have challenges, be positive about it."