Prevalence And Causes Of Blindness And Low Vision Among Adults Aged 50 Years And Above In Luxi County Of Yunnan Province

Objective:To investigate the prevalence and causes of blindness and low vision among older adults aged≥50 years in Luxi county of Yunnan,China.Methods:Cluster sampling size was estimated within an error bound of 0.66%,with 95%confidence limit,2.00 design effect and 90%response rate.Cluster sampling was used in randomly selecting individuals aged≥50 years in 21 of 297 spots in Luxi county in november,2006.Presenting visual acuity was measured by ETDRS(early treatment diabetic retinopathy study)tumbling chart.Eye examinations of external eye,anterior chamber,lens,fundus and so on were carried out by ophthalmologists.A diagnosis of the principal cause for all the eyes with best corrected visual acuity≤0.5 was made as well.The survey was preceded by a pilot study where operational methods were refined and quality assurance evaluation was carried out.The prevalence of blindness was calculated according to the 1973 WHO blindness criterion(criterion A)and presenting vision with blindness criterion (criterion B)and American criterion(criterion C).Results:5575 Individuals were enumerated.The response rate was 92.4%.(1)According to 1973 World Health Organization(WHO)visual impairment criterion(criterion A),the prevalence of bilateral blindness and bilateral low vision was 4.8%and 7.1%respectively,5.1% and 7.1%in females and 4.6%and 7.2%in males,respectively.The prevalence of monocular blindness and monocular low vision was 5.3%and 7.7%respectively, 5.3%and 7.7%in females and 5.4%and 7.8%in males,respectively.The prevalence of blindness and low vision increased with age,decreased with education,unrelated to sex.The survey showed that the most important cause leading to blindness and low vision was cataract.(2)According to the presenting visual acuity and visual impairment criterion(criterion B),the prevalence of severe bilateral blindness and mild bilateral blindness was 5.4%and 8.1%respectively,5.7%and 8.1%in females and 5.1%and 8.1%in males,respectively.The prevalence of monocular blindness and low vision was 3.7%and 17.8%respectively,3.8%and 17.5%in females and 3.7%and 18.1%in males,respectively.The prevalence of blindness and low vision increased with age,decreased with education,unrelated to sex.The survey showed that the most important cause leading to blindness and low vision was cataract.(3) According to the American criterion(criterion C),the prevalence of bilateral blindness and bilateral low vision was 9.4%and 5.6%respectively,9.6%and 5.6%in females and 9.3%and 5.7%in males,respectively.The prevalence of monocular blindness and monocular low vision was 8.5%and 5.6%respectively,8.3%and 5.6% in females and 8.7%and 5.6%in males,respectively.The prevalence of blindness and low vision increased with age,decreased with education,unrelated to sex.The survey showed that the most important cause leading to blindness and low vision was cataract.Conclusions:(1)The prevalence of blindness and low vision in the Luxi area was higher than that in northern,southern china and foreign country.The prevalence of blindness and low vision increased with age,decreased with education,unrelated to sex.The risk indicators of blindness and low vision is age.(2) The leading causes of blindness and low vision in Luxi are,in descending sequence, cataract(78.6%),corneal scar/opacity(5.7%),glaucoma(2.9%),diabetic retinopathy/age-related macular degeneration(2.1%),other retinal/choroids(1.4%)(According to criterion A);cataract(60.4%), ametropia(23.2%),corneal scar/opacity(4.1%),glaucoma(2.0%),age-related macular degeneration(1.9%)(According to criterion B);cataract(78.7%),corneal scar/opacity(5.2%),age-related macular degeneration(2.8%),glaucoma(2.4%), diabetic retinopathy(1.9%)(According to criterion C). (3)The frist important task in blindness and low vision prevention in Luxi is the diminution of cataract blindness by cataract surgery.Reduce the ametropia,ocular fundus diseases,infectious eyes diseases are important too.