Original articlePrevalence of Vision Impairment in Older Adults in Rural China: The China Nine-Province Survey
Section snippets
Materials and Methods
The surveys were carried out in a randomly selected sample of individuals within each county. Major urban areas within the county were excluded. The sampling frame was constructed using geographically defined clusters based on village register data. Cluster boundaries were defined such that each cluster would have a population of approximately 1000 individuals (all ages).
Sample size was based on estimating an anticipated 4% prevalence for visual impairment <20/200 within an error bound
Results
A total of 50 395 persons aged ≥50 years were enumerated, with distribution across age, gender, education and province (Table 1). The mean age of the enumerated population was 62.1 years, ranging from 58.6 years in Xinjiang to 64.8 years in Guangdong. Overall, 45.8% were males, ranging from 42.7% in Jiangxi to 50.2% in Guangdong. Nearly 30% of those enumerated were without education, ranging from 3.69% in Hebei to 62.8% in Yunnan; education at the secondary level or higher was 18.3%, ranging
Discussion
The strengths of this survey were the large, randomly selected sample of participants and use of the same study protocol at each site. Examination response rates generally exceeded 90%, which was achieved by repeat household visits to seek participation and by offering examinations at home when necessary. The notably low examination response rate in Yangxi county (Guangdong) was due in part to the composition of the enumeration team, which was from the urban center of the county in Yangjiang
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Manuscript no. 2009-1182.
A list of study team members for each of the 9 sites appears in Appendix 1 (available online at http://aaojournal.org).
The co-authors from the provinces contributed equally to this work.
Financial Disclosure(s): The authors have no proprietary or commercial interest in any of the materials discussed in this article.
Supported by the Chinese Ministry of Health, Beijing, China; the World Health Organization, Geneva, Switzerland (under National Institutes of Health [Bethesda, Maryland] contract no. N01-EY-2103); and the Lions Clubs International Foundation, Oak Brook, Illinois. The sponsor or funding organizations participated in the design of the study.