Since 1989 she is the Dumbarton Oaks Professor of Byzantine Art History at the Department of History of Art and Architecture at Harvard University, having taught earlier at UCLA and at the Maximilian University in Munich. She began her studies in Germany at the University of Hamburg where she studied Archaeology and Classics. After a visit in the States she decided to continue her studies at the University of California Berkeley in the field of History of Art where she also received her Ph.D. in 1977. She has served as Chair of the Art History department for six years and is a Senior Fellow at Dumbarton Oaks and a member of the Executive Committee and the Editorial Board of Dumbarton Oaks. She serves also on the Board of Trustees at the Cyprus Institute in Nicosia. In the fall of 2023 she became a permanent member of the Academy of Athens.
Of special interest in her research are topics in political and ideological history, as for example the relationship of Church and State, or the use of King David and Moses in imperial propaganda, especially in manuscript illustrations. These questions have led her to investigate the visual evidence ranging from monumental wall paintings and mosaics to objects carved in ivory and steatite, manuscripts and icons. Another topic of special research interest has been the cult of the Virgin Mary. Everyday life and private devotion are further research topics exemplified in her book on Byzantine Icons in Steatite and the large exhibition at Harvard on the role and place of women in Byzantine society with the title Byzantine Women and their World. The role of light and more specifically the sun imagery in the person of the emperor are her most recent research projects.