[Prevalence of blindness and moderate and severe visual impairment among adults aged 50 years or above in Qidong City of Jiangsu Province: the China Nine-Province Survey].

Objective: To estimate the prevalence of blindness and low vision among older adults aged > or = 50 years in Qidong City of Jiangsu Province, China, in 2006.

Methods: Cluster sampling was used in randomly selecting 5662 individuals aged > or = 50 years from September to December 2006 in 16 clusters in Qidong City. The survey was preceded by a pilot study where operational methods were refined and quality assurance evaluation was carried out. All participants were enumerated through village registers followed door-to-door visits. Eligible individuals were invited to receive visual acuity measurement and eye examination. Statistical analyses were performed using Stata/SE Statistical Software, release 9.0. Chi-square test was used to investigate the association of age, gender and education with presenting and best corrected visual acuity.

Results: Five thousands six hundreds and sixty-two individuals were recruited, the response rate was 90.80%. Based on the criteria of World Health Organization visual impairment classification in 1973,91 persons were diagnosed as blindness, 175 persons were diagnosed as moderate and severe visual impairment defined as best corrected visual acuity, the prevalence of blindness and moderate and severe visual impairment were 1.77% and 3.40% respectively. One hundred and thirteen persons were diagnosed as blindness, 354 persons were diagnosed as moderate and severe visual impairment defined as presenting visual acuity, the prevalence of blindness and moderate and severe visual impairment were 2.20% and 6.89% respectively. The prevalence of blindness and moderate and sever visual impairment was higher in aged (trend Chi2 = 825.16, P = 0.000), female (Chi2 = 19.85, P = 0.001), and illiterate persons (trend Chi2 = 329. 85, P = 0.000). The leading cause of blindness was cataract.

Conclusions: Blindness and low vision are associated with older age and illiterates in Qidong City. According to presenting visual acuity, the causes leading to blindness and low vision are, in descending order, cataract, ocular fundus disease, refractive error and cornea disease.