Ningli Wang

Tongren Ophthalmic Center, Capital Medical University

Purpose: To describe the prevalence and causes of low vision and blindness in a rural population in Northern China.

Design: Population-based, cross-sectional study.

Participants: 6830 Han Chinese aged 30+ years was conducted between October 2006 and October 2007 in rural Yongnian County in Handan, northern China.

Methods: Clustered samples of adults aged 30+ years residing in 13 residential villages in Yongnian County of Handan, Hebei Province were randomly selected and invited to participate the Handan Eye Study. Participants underwent a comprehensive eye examination, including standardized visual acuity (VA) tests using logMAR charts. Prevalence was age- and gender-standardized to the 2000 China Census.

Main outcome measures: Low vision was defined as VA < 20/60 but ≥ 20/400, and blindness as VA < 20/400 following the Modified World Health Organization (WHO) definitions. Primary causes of low vision and blindness were determined by study ophthalmologists according to World Health Organization definitions.

Results: 6830 of 7577 (90.4%) eligible individuals participated in the study and 6799 (89.7%) with VA data available. Population-weighted prevalence of presenting bilateral blindness was 0.6% and bilateral low vision was 4.7% for persons 30+ years of age. Based on best corrected VA, the corresponding prevalence of blindness was 0.5% and low vision was 0.9%. Blindness and low vision were strongly age-related. Cataract was the predominant cause of presenting bilateral blindness (36.6%), while under-corrected refractive error was the predominant cause of presenting low vision (35.7%). Myopic retinopathy (11.0%), glaucoma (6.4%) and corneal opacity (5.5%) were other common causes of visual impairment defined using BCVA.

Conclusions: A higher prevalence of blindness and low vision was seen in this rural Chinese sample than has been reported from urban Chinese populations. The estimated numbers with BCVA defined low vision and blindness in 2020, based on best-corrected vision in rural Chinese adults aged 30+ years is expected to be 12.4 million and 2.9 million, respectively. Predominant causes of low vision and blindness in China are treatable.

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