1. Department of Ophthalmology and Visual Sciences; University of Wisconsin- Madison; Madison; Wisconsin; U.S.A
2. Department of Population Health Sciences; University of Wisconsin- Madison; Madison; Wisconsin; U.S.A
3. Division of Epidemiology and Community Health; University of Minnesota; Minneapolis; Minnesota; U.S.A
4. Institute of Statistics; National Chiao Tung University; Hsinchu; Taiwan
5. Department of Community Dentistry and Behavioral Science; University of Florida; Gainesville; Florida; U.S.A