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

Objective To assess the prevalence of blindness and moderate and severe visual impairment among adults aged 50 years or above in the Shunyi district of Beijing,China.Methods It was a population-based cross-section study.Geographically defined cluster sampling was used in 5840 randomly selected individuals aged ≥ 50 years in 28 clusters in the Shunyi district from April to August 2006.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 eight hundreds and forty individuals were recruited and 5118 persons were examined,the response rate was 87.64％.Based on the criteria of World Health Organization visual impairment classification in 1973,57 persons were diagnosed as blindness,160 persons were diagnosed as moderate and severe visual impairment defined as best corrected visual acuity,the prevalence of bhndness and moderate and severe visual impairment were 1.11％ and 3.12％ respectively.Sixty-five persons were diagnosed as blindness,428 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 1.27％and 8.36％ respectively.The prevalence of blindness and moderate and severe visual impairment was higher in aged ( trend x2 =784.23,P =0.000 ),female ( x2 =28.35,P =0.000 ),and illiterate persons ( trend x2 =397.13,P =0.000).Cataract was still the first leading cause of blindness and visual impairment,the retinal diseases was the second.Un-corrected refractive error also was the main cause of visual impairment.Conclusions The prevalence of blindness and moderate and severe visual impairment has been decreasing among older adults aged 50 years or above in the Shunyi district since 1996.The first leading cause of blindness and visual impairment is still cataract. Key words: Prevalence;  Vision disorders;  Cataract;  Middle aged;  Aged