I'd like to ask how blindness in babies or infants is discovered. I'm writing something about a 7-months-old becoming blind through poisoning. Babies do not focus on one object for long, so I guess it'd probably be hard to tell if a baby is blind or not under normal circumstances. I'm having trouble deciding how the parents could finally reach the conclusion that their child is blind.
I'd like to know if anyone has experiences with this kind of situation? How do parents of blind children first discover that they're blind?