Five-year Incidence Of Glaucoma And The Prevalence Of Vision Impairment In Yunnan Minority Areas

Glaucoma is the second most common cause of blindness and the leading cause of irreversible visual loss worldwide. The primary open-angle glaucoma (POAG) is the most frequent type of the glaucoma. Even in developed country the misdiagnosis rate of POAG as high as 50%, so this is an important public health problem. China is a country with the world’s largest number of glaucoma, and the proportion of POAG in glaucoma gradually increased because of the improvement of the diagnosis level. China is a populous country, the majority of the rural population, and China’s vast territory, inhabited by ethnic minorities, and therefore to carry out the rural minority primary open-angle glaucoma epidemiology also has a very important significance. Although several large epidemiologic studies have determined OAG prevalence worldwide, very limited data exist on the incidence of POAG and none from China. This is because incidence measurement requires the longitudinal follow-up of a sizable population cohort over time, which is often require large inputs of manpower, material and financial resources; in addition, the incidence of POAG occult, longer duration, diagnosis is difficult and the low frequency of POAG in most populations leads to relatively small numbers of incident cases, with imprecise estimates.Blindness and visual impairment is a serious social and economic problem worldwide. It not only affects people’s health and quality of life, but also brings a heavy burden to the family and society.2010, WHO published the latest estimates of global visual impairment, moderate and severe visually impaired people are around 246 million, of which approximately 39 million blind. China is one of the countries with most serious blindness and visual impairment.Accurate blindness and visual impairment data will help the World Health Organization and national health agencies to develop effective blindness prevention strategies and rational allocation of limited health resources. Yunnan Province, located in the southwest of China, is one of the most backward areas in China’s social and economic development, and also has the largest number of ethnic minorities in China. This study is a part of Yunnan Minorities Eye Study, we conducted a population-based survey in a sample of elderly Bai and Dai Nationality living in rural areas to understand the incidence and prevention of blindness in Yunnan minority areas. Our results can help to provide a theoretical basis on better prevent and control the incidence of glaucoma and vision impairment in minority rural areas, but also offer the important implications on health policy development and public health planning for glaucoma and vision impairment.Part1:Five-year Incidence of Primary Open-Angle Glaucoma in Ethnic Bai Adults in Dali Rural AreasObjective:To determine the 5-year cumulative incidence and predictors of primary open-angle glaucoma (POAG) in ethnic Bai in rural areas of Southwestern China.Methods:People who were free of glaucoma at baseline underwent the 5 year follow-up examination. Participants underwent comprehensive ophthalmic examinations, including intraocular pressure (IOP) measurement, gonioscopy, cup-to-disc ratio measurement, visual field testing, and stereoscopic fundus photography at both baseline and follow-up. Glaucoma was defined per the International Society of Geographical and Epidemiological Ophthalmology Classification criteria. Multivariable logistic regression models were used to calculate odds ratios (ORs) and 95% confidence intervals (95%CIs).Results:A total of 19 new cases of POAG were detected after a mean follow-up time of 5 years. The 5-year cumulative incidence of POAG was 1.3%(95% CI,0.7-1.9) in this population. The incidence increased significantly with increasing age (P<0.05), from 0.4%(95% CI,0.3-0.4) in people aged 50 to 59 years to 2.1%(95% CI,1.9-2.3) in those aged 70 years or older. Baseline predictors of POAG in this population included an IOP higher than 21mmHg (OR,3.5; 95% CI,2.0-5.9; P<0.001), a vertical cup-to-disc ratio (VCDR) higher than 0.7 (OR,9.7; 95%CI,2.1-45.5; P<0.01) and the presence of myopia (OR 3.6; 95% CI,1.4-8.9; P<0.01). Those with a higher level of education tended to have a lower risk of POAG (OR,0.3; 95%CI,0.1-0.8; P< 0.05).Conclusions:The average annual incidence of POAG in Bai Chinese was lower than that in populations of African-descent and White. The incidence of POAG increased significantly with age growth, at the same time with the intraocular pressure, VCDR, myopic degree increased incidence is increasing. The early diagnosis and treatment rates of POAG in remote western rural areas is low, should cause attention of the Government and relevant health departments. The results are important for clinical management and health resource allocation in rural areas of China.Part 2:The prevalence of blindness and vision impairment in rural Ethnic Dai and YiPurpose:To assess the prevalence and causes of visual impairment(Ⅵ) in the elderly Dai and Yi Nationality in rural areas.Methods:Random cluster sampling was used to identify the adults Dai and Yi Nationality 50 years and older living in the Jinghong and Shilin of Yunnan province, China. Presenting visual acuity (PVA) and best-corrected visual acuity (BCVA) were measured using the Early Treatment Diabetic Retinopathy Study visual chart. Blindness and vision impairment were defined according to World Health Organization criteria. The major cause of visual impairment was identified for participants with visual impaired.Results:一、The results of Dai Nationality1.2150 Dai nationality (80.5% participation rate) adults of the age of 50 years and older were examined and tested for VA. The participation rate were associated with ages and gender. Examination rate increased with age and female significantly higher than male.2. With PVA, the prevalence of blindness and visual impairment was 2.98% and 13.35%. When the BCVA as employed, the rates were reduced to 2.14% and 6.74%. The prevalence of blindness were associated with older age and sex, whereas not correlated significantly with lack of education.3. Based on the BCVA, the principal causes for blindness in Dai nationality were cataract (73.91%), followed by glaucoma(8.70%) and myopic maculopathy (6.52%); the principal causes for vision impairment were cataract (66.90%), followed by age-related macular degeneration (11.03%) and myopic maculopathy(7.59%).Based on the PVA, the principal causes for blindness were cataract (68.25%), followed by myopic maculopathy(9.52%) and glaucoma (6,35%),the principal causes for vision impairment were cataract(62.98%), refractive error(11.76%) and age-related macular degeneration (6.57%).二、The results of Yi Nationality1.2214 Yi nationality (81.0% participation rate) adults of the age of 50 years and older were examined and tested for VA. The participation rate were associated with ages and gender. Examination rate increased with age significantly higher than male.2. With PVA, the prevalence of blindness and visual impairment was 2.1% and 19.1%. When the BCVA as employed, the rates were reduced to 1.7% and 8.2%. The prevalence of blindness were associated with older age and significantly with lack of education.3. Based on the BCVA, the principal causes for blindness in Yi nationality were cataract (71.1%), followed by age-related macular degeneration (10.5%) and corneal opacity (5.3%); the principal causes for vision impairment were cataract (66.7%), followed by myopic maculopathy(7.8%) and age-related macular degeneration (6.7%). Based on the PVA, the principal causes for blindness were cataract (63.0%), followed by age-related macular degeneration (10.9) and myopic maculopathy(6.5%), the principal causes for vision impairment were cataract(69.4%), refractive error(7.6%) and age-related macular degeneration (4.5%).Conclusions:A higher prevalence of blindness and vision impairment was seen in Dai and Yi nationality sample than that from other similar study in China. As potentially treatable eye diseases, cataract and uncorrected refractive error are the most important causes of visual impairment among the Dai and Yi nationality. Blindness prevention programs targeting the rural elderly should be expanded, particularly in areas with limited access to and affordability of eye care services.