Avoidable blindness and value based healthcare: more value with a population approach - Giovanna Elisa Calabrò; Roberta Pastorino; Luca Giraldi; Maria Emanuela Frisicale; Agnese Lazzari; Giovanni Capelli; Fulvio Luccini; Carlo Favaretti; Andrea Silenzi (Epidemiology, Biostatistics and Public Health)