One week before the spring recital, seven young ballerinas stand in formation, awaiting their cue.

In the back, Sofia Priebe - at 4 feet, 8 inches - is the second-tallest girl in her class at Mystic Ballet. Where the others stare measuredly ahead, doe-eyed, Sofia squints in the 5:30 p.m. light reflecting dimly off the mirrored wall at the back of the studio.

Their instructor presses "play" and the first string swells of the waltz ring out. The girls leap forward, row by row. Sofia moves last, as gracefully as can be expected of a 10-year-old swathed in taffeta. When her downbeat arrives, she nods her head slightly, moves her outstretched arms stiffly downward in one short pulse, and she's off.

Four minutes and 50 seconds of prim three-quarter time later, Sofia finishes, chin up, arms over her head, fingertips centimeters apart.

She's been practicing ballet for six years now. She is legally blind.

At age 4, Sofia was diagnosed with Leber's congenital amaurosis, a rare genetic disorder that occurs in just 3 out of 100,000 births, according to the American Association for Pediatric Ophthalmology and Strabismus. In its most basic explanation, the eye's photo receptor cells, the so-called cones and rods that detect light and color, deteriorate over time. Eventually, they stop working.

While many LCA babies are born completely blind, Sofia can make out shadows, shapes and some detail up close, though her peripheral vision is next to none. Her depth perception is faint. Colors have faded over the years. Dim light makes it easier; too much light washes everything out, sometimes painfully so.

"If it's a bright light," says her father, Charles Priebe, "or if it's a bright, sunny day, she's lost."

Sofia's eyesight dropped off drastically between the ages of 2 and 4. While for years she has plateaued, her colors have been going. Darker colors especially - reds and browns, Sofia says - muddy together.

"When she was first diagnosed at 4, we were told the best we could expect was that she'd have some perception of light through the end of high school," says Laura Manfre, her mother.

That prognosis has varied since. It could be the end of high school; it could be her late 20s or 30s. One day, Sofia will be completely blind. It's just a question of when.

• • •

Sofia was born on Valentine's Day - 8 pounds, healthy, a headful of hair - in 2003 just outside of Atlanta, 2½ hours northwest of where her parents met while working for Habitat for Humanity International.

Her disability revealed itself incrementally, in symptoms often easily chalked up to a toddler's clumsiness.

At her day care program, when the staff would dole out palmfuls of Cheerios, Sofia would pat her hand around aimlessly, unsure of where to grab. Toddling down the stairs, she'd miss a step or two. And crawling over the carpet, where the fabric ended and the floor began, Sofia would pause, unsure whether the color change meant the edge of the carpet or the edge of the ground, nowhere to go.

Her parents figured she was nearsighted and bought her a pair of tiny white-rimmed glasses.

Then the strabismus began, one of her eyes lolling inward. And finally, the nystagmus - the rapid, involuntary oscillating of her eyes, pupils flitting fast, left to right and back.

"It was always a series of different things that then sort of added up," Laura says.

• • •

When the doorbell to her family's house on Chriswood Trace in Ledyard rings one evening, Sofia is the first one to answer. She tilts her face upward into the fading sunlight, squeezing her lids shut.

When she opens them again, there is nothing cloudy about her bright brown eyes, nothing to suggest they are anything but functional. Her shoulder-length hair is brown and wavy, center-parted, tucked behind her ears. Her blue nail polish is chipped, her hands stained with red marker from an earlier art project.

She takes the stairs two at a time, just grazing the banister with her left hand. In jeans, threadbare at the knee, and a blue T-shirt, she makes her way up to give a tour of her room, one that speaks of a 10-year-old beginning to outgrow a childhood of floral-patterned dresses.

On her desk, there's a heap of Legos with which she and her brothers build houses, and a closed-circuit television that resembles an old-school computer monitor. Using its magnifying lens, Sofia can curl up in her chair, press some buttons to get the right light saturation, put her face up close to the screen and read her books.

In here, her mother has to fight the urge to flip on the light switch. Sofia doesn't do well with the quick transition from dark to light.

• • •

Sofia's parents first took her to have her eyes tested just before she turned 2. An ophthalmologist in Atlanta slipped a patch over one of her eyes, to no response. But when he patched the other, Sofia - normally an easygoing baby, Laura says, the kind who sleeps through the night - suddenly began to scream and cry.

"And he looked at me and goes, 'Oh my gosh. I don't know how much she can see at all out of that eye,'" she says.

The family moved to Ledyard shortly thereafter, and Sofia saw several doctors in Connecticut. The diagnosis came after a referral to a specialist at Boston Children's Hospital, where an electroretinogram - like an EKG, but for the eye - showed that things weren't firing the way they should. The bloodflow to her eyes had ceased, the nerves deadened from disuse.

• • •

In Sofia's ballet class - save for the yellow "Mystic Ballet" decal ironed onto his track jacket - the instructor wears all black.

For those with 20/20 vision, the contrast between him and the pale pink walls is striking. To Sofia, it makes all the difference.

Ballet works for her, Laura says, because of the structure - strict positions and confines for Sofia to work within, voiced directions she can follow. The dark silhouette demonstrating at the front of the room helps, too.

Sofia takes several measures to amplify what eyesight she has, and uses a number of tools to work around it. She has sunglasses to wear outside at recess at Ledyard Center School, and a habit of breaking them. They buy cheap ones now.

At home, for writing, there's the Brailler, a heavy, silver typewriter contraption with noisy keys and the tinny brrring sound of the carriage return, its keys corresponding to the six-dot matrix of the Braille code.

On the higher-tech side, Sofia uses her closed-circuit TV or enlarges a TV screen or text with her iPad. But reading print is laborious. Each word must be magnified many times so Sofia may make it out, scrolling along one by one.

When her eyes are tired at the end of the day, she resorts to Braille to read her favorite books - fantasy, dragons and mythical creatures, Harry Potter.

When she grows up, she says, she wants to be an author.

• • •

The move from Atlanta to Connecticut when Sofia was 3 came when Charles got a job building Navy housing in Groton and Newport.

He was laid off in early 2008 when the construction industry crashed. Laura works for a mobile technology company in Rhode Island.

The job market has been tough, but they've chosen to stay in the area partly because of the state Bureau of Education and Services for the Blind, which has provided Sofia with a Braille teacher to work with her at school and with all the technology she uses at school and at home. A paraprofessional works with all of Sofia's teachers to make sure the materials are prepared in Braille, large print or an otherwise tactile way that allows her to participate.

More than 70 percent of blind people are unemployed, according to most sources. They are among the most educated of people with disabilities. They sit home and read or write, Laura says, but then they don't go out and get jobs.

Sofia won't be a part of that statistic, she says. "She's brilliant, and she'll do whatever she wants to do," she says.

Sofia doesn't own up to it outright. But sometimes something will set her off - a frustrating school assignment, a ballet step she can't master.

"She doesn't like to be different," Laura says. "She doesn't like to be told she can't do things."

• • •

The best time of day is dusk. The best place is around the house and in the yard, where the corners and furniture are familiar, and Sofia doesn't have to think much about what she might bump into or fall over.

Still, there are incidents. She's walked into trees; she's fallen down stairs. Three months back, she bruised her nose when an unseen door slammed in her face.

Sofia doesn't like to use her cane. Strangers will walk right up to her, Laura says, and just stare.

"People are rude," Charles says. "They are horribly rude."

Once, a group of chattering kids all quieted at once when Sofia walked up to pass through them - a gauntlet of cruel silence. It was indoors, the light low enough for her to register that all eyes were on her.

"She's definitely self-conscious, just like any other 10-year-old," Laura says.

The daily physical exchanges made while walking down a crowded hallway - those slight, almost unconscious shifts made to accommodate someone else's trajectory - are all lost on Sofia.

In these situations, the cane is a signal to others: Maybe move aside, maybe hold the door.

For the most part, people are kind. But acceptance and encouragement are one thing; understanding is another.

"She doesn't feel sorry for herself. So when other people feel sorry for her, I find it difficult," her mother says.

• • •

Last July, at an LCA conference, Sofia and her parents sat in a room full of blind people and their families. They were told that things are moving so quickly, every blind person in that room could expect to see someday.

For the last few years, Sofia's parents have searched for a genetic diagnosis to match the clinical one - the key to a cure.

Each clinical trial is associated with the specific gene culprit, so half the battle was determining which was causing Sofia's LCA. In 2008, she met the team responsible for the first successes at The Children's Hospital of Philadelphia.

After a few years of unsuccessful testing, Sofia and her family got the preliminary results three months ago. The responsible gene was identified as IQCB1.

Sofia understands that, save participation in a successful clinical trial, her future is one without sight. She'd be fine with it, she says, as long as she has a seeing-eye dog.

And if she could see?

"That would be cool," she says hesitantly.

Now that she has her genetic answer, Sofia doesn't often ask why anymore. But there are the harder days when she's looking for a perhaps more philosophical explanation.

"I don't know why you have it. And we're not really sure what's going to happen, so we're just gonna prepare for you losing all your vision, but we're gonna hope that someday you won't. And meanwhile, you're doing great," Laura will say. "So who cares, right?"

Even if a cure were available today, Laura isn't sure Sofia would be interested. She's happy now, Laura says, exactly the way she is.

a.isaacs@theday.com

If you want to help

To donate to the Foundation for Retinal Research, visit sofia.kintera.org. Proceeds go to funding gene therapy research for LCA patients with Sofia's gene type, IQCB1.