Dr. Onan graduated from The University of Texas at Austin with a Bachelor of Arts degree in economics with highest honors. She then earned a Doctor of Medicine degree with honors from Baylor College of Medicine in Houston, where she was a Presidential Scholar. She completed a transitional internship at St. Joseph Hospital in Houston followed by an ophthalmology residency at the Cullen Eye Institute at Baylor College of Medicine. Her training in pediatric ophthalmology and adult strabismus was completed at Texas Children's Hospital. Dr. Onan served as Clinical Instructor of Ophthalmology at UT M.D. Anderson Cancer Center from 2000 to 2001. After a year in practice in Seattle, Washington, she returned to Texas in 2002. She has been the Chief of Pediatric Ophthalmology at Dell Children's Medical Center since 2008 and manages the consult and teaching services at the hospital. She is active in community education and residency training and has taught numerous pediatric, ophthalmology and transitional residents as well as giving lectures on the eye findings in child abuse in Central Texas.
Dr. Onan is board certified by the American Board of Ophthalmology. She is a member of the Travis County Medical Society, Texas Medical Association, Austin Ophthalmological Society, and the American Academy of Ophthalmology. Dr. Onan has also been awarded Texas Monthly's Super Doctor for the past four years (2006-2009).