1. Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, Massachusetts, USA
2. Bascom Palmer Eye Institute, Department of Ophthalmology, University of Miami, Miami, Florida, USA
3. Grupo de Investigacion Escuela Barraquer, Escuela Superior de Oftalmologia del Instituto Barraquer de America, Bogota, Colombia
4. Department of Ophthalmology, Miami Veterans Administration Medical Center, Miami, Florida, USA