Lee, who had previously been sidelined after breaking his wrist April 19, said the cause of the child's illness was still unknown, the Chicago Sun-Times reported Monday.
"We've had a family emergency. It has to do with our daughter," Lee said Sunday. "Until we get this cleared up, I won't be with the team.
"My daughter's lost some vision in one eye, and until we find out more at a later time ... right now we have to go through some more tests," he said. "We just ask for everyone's prayers. We need a miracle and we ask for your prayers. We need everyone to believe she's going to be OK."
"You break your wrist and you think that's a big deal," Lee said. "Then something like this happens, and it really slaps you in the face. It's all about your loved ones and your family."
Teacher apologizes for showing sexual image of herself in class
Interpol investigating stolen passports on missing flight