When Christine and Forrest Bray adopted Opal, a ­4-month-old blind and deaf Australian shepherd mix, they worried about what she couldn’t do.

She couldn’t hear when they called for her, she couldn’t go up and down stairs, she couldn’t play fetch because she couldn’t see the ball.

But Opal soon proved that her senses of smell and touch make her just as capable as other dogs.

Christine Bray, 28, took a video of Opal sensing when Forrest Bray, 35, got home from work. In the video, Opal sticks her nose in the air and begins to wag her tail as Forrest gets out of his truck. By the time he walks into the yard, Opal is barking and jumping, clearly excited to greet her human dad.

When Christine Bray posted the video on social media, it went viral. The couple from Spokane Valley, Washington, realized that what Opal was able to accomplish, despite her disabilities, is what makes her so impressive.

Christine Bray hopes to share that message with her daughter, Lily, when the 4-month-old grows old enough to possibly feel ashamed of Opal for being different. She self-published a book this month that she wrote not just to explain to Lily how to communicate with Opal — two taps on her back to sit, two taps on her shoulders to lie down — but also that she shouldn’t be embarrassed that her dog is disabled.

“Opal may be different than the other dogs, but she is far from being an underdog,” Bray wrote in the book.

Opal, like many other dogs born with what’s called double merle genes, is able to use her other senses, such as smell and touch, to make up for what she can’t see or hear.

When two dogs with the merle gene, which is what makes coats whiter, are bred together, their puppy has a 25 percent chance of being born a double merle.

While one merle gene causes a marbling effect on the coat, a double merle removes the pigment, or color, from the dog’s coat and makes it likely that the dog will be deaf, blind or both.

Amanda Fuller, who runs a dog rescue for deaf and blind dogs and is a vet technician in Baltimore, said this can happen to any breed that has the merle gene, including Great Danes, border collies and a type of corgi.

While most professional breeders know not to breed dogs that may produce a double merle dog, inexperienced breeders may not, Fuller said. She encourages greater education on the topic and has helped create and share videos to teach people.

“The big thing with this problem is that it’s preventable,” Fuller said. “A majority of these dogs are being bred out of ignorance.”

Another lesson Fuller says is important to understand is that the dogs are capable and happy.

“Our dogs are no different than any other,” she said.

In the two years the Brays have had Opal, she’s learned to play catch by feeling for the ball, and go up and down stairs. She has other talents, too. She can sniff out an ice cube left on the Brays’ kitchen floor. She never runs into furniture unless someone moves something.

The Brays are impressed by how sensitive Opal was to Lily. A few days after they brought the baby home from the hospital, they cautiously let Opal into the same room as Lily. She ran toward the family, but within a few feet, she slowed down, put her ears back and slowly approached the newborn.

“It’s such a strange thing to see this crazy dog calm down within an instant,” Forrest Bray said.

Opal also gets along with other dogs, including Pearl, a 1-year-old deaf terrier mix, whom the Brays adopted after the video went viral.

Christine Bray said getting Pearl was a reaction to people who saw the video and criticized the couple, telling them Opal needed a seeing-eye dog. The Brays later realized Opal doesn’t need the help and is a perfectly happy dog.

“She doesn’t know she’s different, because she was born this way,” she said.