1. Ophthalmology Service Hospital Universitario Miguel Servet, Faculty of Medicine, University of Saragossa, Saragossa, Spain
2. Department of Ophthalmology, Clínica Universidad de Navarra, Faculty of Medicine, Universidad of Navarra, Pamplona, Spain
3. Ophthalmology Service, Hospital Clínico San Carlos, Faculty of Medicine, Universidad Complutense de Madrid, Madrid, Spain
4. Unidad de Estadística, Department of Biochemistry and Genetics, University of Navarra, Pamplona, Spain