1. From the Department of Twin Research and Genetic Epidemiology, King's College London School of Medicine, London, United Kingdom;
2. the Centre for Eye Research Australia, University of Melbourne, Royal Victorian Eye and Ear Hospital, Melbourne, Australia;
3. the Department of Ophthalmology, Duke University Medical Center, Durham, North Carolina; and
4. From the Department of Twin Research and Genetic Epidemiology, King's College London School of Medicine, London, United Kingdom; the 4Princess Royal University Hospital, Bromley Hospitals NHS Trust, Orpington, United Kingdom.