As for Hazel's favorite print? "Mermaid," the Busby daughter tells PEOPLE. Hazel was born with an eye condition called congenital nystagmus, which is "an involuntary eye flutter," Adam explained.

Discover how the genetics behind your eye color connects to various health conditions, from melanoma risk to pain ...

with one blue eye and an iris that is a mixture of blue and hazel. A detail that gives her a captivating charm. Far from being a flaw, heterochromia is a unique trait that enhances the people who ...

For people with green or hazel eyes, one or both of the layers of the iris contains light brown pigment. The light brown ...