The Rotterdam Study21 is a prospective population-based cohort study of cardiovascular, locomotor, neurologic, and ophthalmologic diseases in older subjects. In summary, all inhabitants 55 years or older living in Ommoord, a suburb of Rotterdam, the Netherlands, were invited to participate in the study. Of 10 275 eligible individuals, 7983 (77.7%) participated. The ophthalmologic part of the study started after screening of the participants had begun, leading to 6780 ophthalmic participants, also with a 78.1% response rate. The Rotterdam Study was approved by the medical ethics committee of Erasmus University, and written informed consent was obtained from all participants. Baseline examinations, including a standard home interview and physical examination at the research center, took place between March 20, 1990, and July 31, 1993, and were followed by 3 examinations from September 1, 1993, to December 31, 1994 (response rate 88.2%), from April 15, 1997, to December 31, 2000 (response rate 80.1%), and from April 23, 2002, to December 31, 2004 (response rate 74.3%).