It can't be easy raising the country's only all-girl set of quintuplets plus a five-year-old, especially when one of them needs additional care. OutDaughtered star, Hazel Grace, is only two-years-old, but she has a health issue that has fans — and her parents —concerned.

The toddler has a condition known as Nystagmus, a vision impairment in which the eyes make repetitive, uncontrolled movements. During season 2, the parents discussed Hazel undergoing surgery, which wouldn't actually fix her vision but would "correct the placement of where her eye goes to focus better so she doesn’t have to turn her neck, which is a huge deal," Danielle said.

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The procedure carries a 1-in-100,000 risk of permanent vision loss which to most, may be a relief, but to Adam, it's terrifying. "To most people, that would sound like, 'Man, that's pretty good odds,'" Adam told the cameras at the time. "But then whenever you think of our situation, our chance of having all-girl quintuplets was 1 in 64 million. And so odds don't really do it for us now."

The other quintuplets – Ava Lane, Olivia Marie, Riley Paige, and Parker Kate – were born at 28 weeks on April 8, 2015, in Houston and went home from the hospital in July. Although they're all healthy, the couple worries Hazel will be left behind. "She's still the only one who isn't walking yet, and it sucks," Danielle said last year. "I know they all kind of develop and grow [at] their own pace, but I don't want her to be left behind or not be able to hang with her sisters."

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Adam — clearly frustrated — chimed in, "What is wrong with Hazel? I noticed Hazel over there, just playing on the foam mat by herself, and then all the other girls are out running around and playing with each other and stuff. You just have it in the back of your mind that I know that Hazel is lagging a little bit behind right now physically," he continued. "But now that she's not going to school, is that affecting her socially and her social interactions with other people?" The girls are now in nursery school twice a week, and we're hoping little Hazel will be able to keep up! We have a feeling she'll be just fine. After all, she has quite a large support system!