Title:
[Prevalence survey of visual impairment in a multiethnic rural district in the high altitude area of Yunnan Province, China].

Abstract:
To estimate the prevalence and causes of visual impairment by a population-based survey conducted in Gongshan County of Yunnan Province.
Cluster sampling method was used for sample selection. In person interview, pilot study, visual acuity (VA) check, intraocular pressure, slit lamp microscopy and fundus examination were performed. The diagnoses of blindness (VA<0.05) and visual impairment (VA<0.3 to ≥0.05) were based on best-corrected visual acuity in the better eye. The prevalence of visual impairment was calculated as to age, gender, education, ethnic group and altitude of living area. The dominant causes of blindness and visual impairment were then identified. The comparison of prevalence among different group examined by four-fold table Chi-square test, R×2 Chi-square test and trend Chi-square test.
Among 3070 eligible residents, 2460 (80.1%) were finally enrolled in the present study. The total prevalence of visual impairment was 6.46%. The bilateral blindness and unilateral blindness was 19 and 46 respectively. The bilateral and unilateral low vision was 49 and 45 respectively. There was no statistical significant difference of prevalence of visual impairment among different ethnic groups (χ2=0.75, P=0.388). There was significantly statistical difference of prevalence of visual impairment among groups who lives in different altitude area (χ2=18.34, P=0.000). High prevalence were also observed in the elder (≥70 years), illiterate and outdoor-workers, which was 2.24%, 4.19%, 5.65% respectively. The leading causes of bilateral blindness was cataract (42.1%, 8/19), corneal opacity (26.3%, 5/19), and retinal abnormality (21.1%, 4/19). The leading cause of bilateral low vision was also cataract (42.9%, 21/49).
Cataract was the dominant cause of visual impairment in Gongshan County of Yunnan Province. The study highlights an urgent need of visual impairment prevention program conducted by local public heath intervention, especially focusing on cataract treatment.