Emmett T Cunningham1,2,3, Manfred Zierhut4. 1. a The Department of Ophthalmology , California Pacific Medical Center , San Francisco , California , USA. 2. b The Department of Ophthalmology , Stanford University School of Medicine , Stanford , California , USA. 3. c The Francis I. Proctor Foundation , UCSF School of Medicine , San Francisco , California , USA. 4. d Centre for Ophthalmology , University Tuebingen , Tuebingen , Germany.