My daughter has blue sclera. why?

Normal: Depending on age, sclera can be kinda thin, so underlying tissue shows through. Nevus of ota is another syndrome- needs to be evaluated by ophthalmologist. Other rare diseases can also cause blue sclera.

See below: Blue sclera maybe normal. Or, it may be associated with a rare illness called osteogenis imperfecta. With the latter, your child would have multiple fractures. Discuss with your doctor.