1. Department of Ophthalmology University Clinical Hospital of Valladolid Valladolid Spain
2. Institute of Applied Ophthalmobiology (IOBA) University of Valladolid Valladolid Spain
3. Medical School University of Valladolid Valladolid Spain
4. Department of Statistics. Medical School University of Salamanca. Salamanca Biomedical Research Institute (IBSAL) Salamanca Spain
5. Cooperative Network for Research in Ophthalmology (Oftared) Carlos III National Institute of Health, ISCIII Madrid Spain