LEWISVILLE, Texas — The new companion in Zach Thibodeaux's life is young and blond, with a moist nose that snuggles in close whenever opportunity allows.

Natura, a 20-month-old Labrador retriever, is the Lewisville boy's latest bid for independence as he moves toward a life of blindness.

It's been more than a year since Zach, a 9-year-old third-grader, was diagnosed with cone-rod dystrophy, an incurable disease quickly stealing away his eyesight. With just slivers of his vision remaining, Zach sees Natura mostly as a shadow, a vaguely golden shape at his side.

Natura became a part of Zach's life three months ago as part of the K9 Buddy program run by California-based Guide Dogs for the Blind. By providing visually impaired kids and adults with canine companions, K9 Buddy aims to foster independence and the prospect, should they choose, of having an actual guide dog someday.

"Basically, it's to teach them the responsibility of having a dog, so when it's time to receive their own guide dog they know how to live with a dog as well as work with one," said Sandi Alsworth, who oversees Guide Dogs for the Blind's puppy-training efforts in Texas and Arizona.

Zach is learning to be fully in charge of Natura's behavior and well-being, meaning he could qualify for a guide dog as early as age 14. Typically, recipients must be 16.

"We'll be watching him grow into a natural guide-dog user as he ages," Alsworth said.

As Zach is proud to point out, he's just one of seven kids in the U.S. to have a dog like Natura. "And the only one in Texas," he said.

For Zach, having a dog not only spurs maturity, it's improving his cane skills and providing companionship during what is increasingly an isolating disability.

Zach knows the situation is a trial run of sorts. He and Natura are constantly together; they play fetch and tug-of-war.

"It's just more fun to have a dog and not be alone," Zach said.

Zach has long been fond of animals, and last year, Johanna Uek, his mother, got him a pair of dogs — a small terrier and a Chihuahua mix — to help ease the stress of dealing with his worsening condition.

Those dogs moved on to a relative's house with Natura's arrival. Despite her larger size, she's a typical puppy, bounding up and down stairs, tongue lapping, tail whipping side to side.

Zach called her over one morning at his father's Addison townhouse and slid a red muzzle over her snout as she obediently waited, all business.

"When that leash is on, it's work time," Adam Thibodeaux said. "Her personality changes."

They stepped outside and toward the small park abutting the complex. It was cold and wet, but Zach knew this was something he had to do.

He sensed the damp air, the soggy soil. "It rained again last night?" he asked as Natura wandered onto a patch of grass and circled, sniffing the ground.

"Give her a longer leash, Zach," his father said. "She's got a real short leash right now."

They began their stroll, a morning-chat routine for Zach and his dad. Natura, docile and content, knew the route now, a winding path barely an eighth of a mile long.

"Natura is different," Zach said. "My other dogs, they scream. They blow up: RAAR RAAR RAAR RAAR!"

The two actually met last summer. But only by chance did they reunite.

After Zach applied for a companion dog through the K9 Buddy program, Guide Dogs for the Blind called on Beth Allen, co-founder of newly launched Lone Star Puppy Raisers in Garland, whose members train puppies to become full-fledged guide dogs.

Natura had been among the new group's first six puppies, and when Allen stopped by Zach's home to assess his readiness for a dog, she brought Natura with her.

"It was just a fluke that they were able to meet," Allen said. "They got to walk down the street a little bit together."

The two obviously clicked. But Natura was already on her way toward becoming a guide dog. By Labor Day weekend, she was headed to California to be matched with a visually impaired person in the Bay Area.

But during the transition, she showed signs of stress — first on the plane, then during the loud mechanized noise of a ramp being lowered on a van for the disabled.

"That's a huge part of what guide dogs do," said Guide Dogs for the Blind's Alsworth. "It was asking too much of her. . That's trauma they didn't want to put her through on a daily basis."

Natura had a change of careers.

"Only 60 percent of dogs who go through the training end up working as guides," Allen said. Some instead become companion dogs for diabetics, search-and-rescue dogs or therapy dogs.

Natura was placed in the K9 Buddy program, and though Alsworth recalled the dog's affinity for Zach, the two flights she'd have to take from Northern California to Dallas would be terrifying for her.

Response came quickly after she explained the situation in an email. Within minutes, someone had volunteered to drive Natura from Los Angeles to Palm Springs.

More emails and phone calls followed as a relay system fell into place. "I had three MapQuest screens up," Alsworth said. "I had no clue where these people lived."

Ultimately, Natura's four-day trek to Dallas unfolded in six legs. Alsworth herself was part of so-called Team Natura, driving the last leg from Phoenix with another volunteer and arriving in time to meet Zach on New Year's Day.

"He was quite surprised," Alsworth said. "It was a touching moment for all of us."

Don't pull the leash till you've asked her to come to you. Hold the kibble to your waist so she'll come to your side. Don't pet Natura before she's finished a task or she'll think she's done.

The instructions fly as Alsworth helps Zach with his dog-handling skills on a frigid February morning.

"See what happened there?" she said after Zach called Natura over, noting that the dog actually came to him before the order. "Why? Because you did this."

She yanked the leash. "So she had the option of either having her head pulled off or coming with you," Alsworth said. "Wait until you say 'come' to pull."

Alsworth said having a dog will provide Zach with what she called "a bridge to society," sparking interaction.

"When you have a cane, people move out of the way," she said. "When you have a dog, people come toward you."

In coming years, Zach will attend Lone Star Puppy Raisers meetings to continue Natura's training and hone his own dog-handling skills.

"She has totally bonded with Zach," his father said. "They're really a pair now."

And Zach's parents, who are divorced, agree the experience is teaching their son to empathize with the duties of parenthood.

"It's building his confidence," Uek said. "He's learning to take care of something other than himself."

Thibodeaux said Zach has had to learn to put off playing his video games after school until he feeds Natura and takes her for a walk.

"That's been the best thing about this," he said. "I've seen Zach grow into responsibility."

Nine-year-old Zach Thibodeaux is going blind, the result of a condition called cone-rod dystrophy, a degenerative disease for which there is no cure. In " Zach's Journey," staff writer Marc Ramirez and staff photographer Tom Fox are chronicling the Lewisville boy's passage into darkness.