Mum Tara Taylor uploaded a photo of her toddler Rylee, three, onto the social networking site and was immediately alerted by concerned friends.
Tara told WREG: "They said 'Hey, I'm sure it's nothing. It's probably the lighting, but your daughter's eye is glowing and you might want to have it checked out because it's a sign there could be an issue with her eye'."
Her mother took her friends' advice and took Tara to see a doctor who diagnosed her with Coats' disease - a condition which can result in blindness.
Dr. Jorge Calzada, of the Charles Retina Institute and Baptist Eye Clinic, in Memphis, Tennessee, said the disease was usually caught in an 'unexpected way'.
He said: "The significant problem we have with children is that a child won't say, 'Mommy, I can't see out of my right eye'.
"When a child recognises he cannot see or the parent recognises they cannot see, it's often because they've lost vision in both eyes."
Because the disease was spotted early, doctors are confident Rylee can be successfully treated and her vision saved.