Dr. McDonnell is the Director and William Holland Wilmer Professor of Ophthalmology at the Wilmer Eye Institute at the Johns Hopkins University School of Medicine. Dr. McDonnell was the Irving H. Leopold Professor and Chair, Department of Ophthalmology, University of California, Irvine, January 1999-2003. Dr. McDonnell was Professor of Ophthalmology, University of Southern California, Los Angeles July 1994-2003. Dr. McDonnell was the Co-Founder of GrayBug Vision, Inc. He is a Member of the Board of Directors of Allergan, Plc.

Dr. McDonnell earned his MD from John Hopkins University.