Question : A multicentric study was conducted to determine the association between diabetes and cataract. The investigators recruited 1000 diabetics and 2500 non-diabetics. The participants were examined to exclude presence of cataract at the time of recruitment. They were followed once yearly for 10 years to document the development of cataract. The study found that the incidence of cataract among diabetics was more when compared with the non-diabetics. Identify the study design in this study?