Xin Rong Duan

Prevalence and Causes of Low Vision and Blindness in a Rural Chinese Adult Population. The Handan Eye Study

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 A study of 6830 Han Chinese aged 30 years and older was conducted between October 2006 and October 2007 in rural Yongnian County in Handan, Northern China. METHODS Clustered samples of adults aged 30 years or more residing in 13 residential villages were selected randomly and were invited to participate the Handan Eye Study. Participants underwent a comprehensive eye examination, including standardized visual acuity (VA) tests using logarithm of the minimum angle resolution 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 was defined 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 WHO definitions. RESULTS Six thousand eight hundred thirty (90.4%) of 7577 eligible individuals participated in the study, and 6799 (89.7%) had 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 and older. Based on best-corrected visual acuity (BCVA), the corresponding prevalence of blindness was 0.5% and that of low vision was 1.0%. Blindness and low vision were strongly age related (P<0.05). Cataract was the predominant cause of presenting bilateral blindness (36.6%), whereas undercorrected refractive error was the predominant cause of presenting low vision (78.4%). After refractive correction, cataract became the first leading cause of blindness (41.9%), and low vision (48.2%), myopic retinopathy (16.1%), glaucoma (9.7%), and corneal opacity (9.7%) were other common causes of blindness 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 or more, is expected to be 12.4 million and 2.9 million, respectively. Predominant causes of low vision and blindness in China are treatable.

Normal Macular Thickness Measurements Using Optical Coherence Tomography in Healthy Eyes of Adult Chinese Persons: The Handan Eye Study

PURPOSE To describe macular thickness measured by optical coherence tomography (OCT) in healthy eyes of adult Chinese persons. DESIGN Population-based cross-sectional study. PARTICIPANTS Chinese adults aged 30+ years who were residents of Handan, North China. METHODS The Handan Eye Study is a population-based study of eye disease in Chinese persons. Eligible residents underwent a comprehensive ophthalmic examination including OCT (Stratus OCT, Carl Zeiss Meditec Inc., Jena, Germany). Fast macular thickness scans were performed over maculae within 6 mm in diameter, divided into 3 regions (central, inner, and outer, with a diameter of 1, 3, and 6 mm, respectively) and 9 quadrants (1 in the central region and 4 each in the inner and outer regions). Retinal thickness (means and standard deviations) was calculated by OCT mapping software, presented for foveal minimum, central macula (within 1 mm diameter), and inner and outer regions divided by 8 quadrants. MAIN OUTCOME MEASURES Macular thickness measured by OCT. RESULTS Of the 6830 participants (90.4% response rate) examined, 2230 eyes of healthy subjects with high-quality OCT scans were selected (32.7% of participants; mean age, 46.4+/-9.9 years, 58.4% were women). The mean foveal minimum, central, inner, and outer macular thicknesses were 150.3 (18.1) microm, 176.4 (17.5) microm, 255.3 (14.9) microm, and 237.7 (12.4) microm, respectively (overall differences, P<0.001). The mean foveal volume was 0.139 (0.014) mm(3), and the mean total macular volume was 6.761 (0.516) mm(3). In the inner region, the nasal quadrant was thinner than the superior and inferior quadrants, and in the outer region, the nasal quadrant was the thickest (P<0.001). Age was positively correlated with foveal (beta coefficient = 3.582) and central macular (beta coefficient = 2.422) thicknesses. The foveal minimum, central, inner, and outer macular thicknesses were significantly greater in men than in women. Fasting plasma glucose was negatively correlated with central macular thickness (2.416 mm reduction per millimole/liter increase in glucose), and axial length was positively correlated with central macular thickness (2.138 mm increase per millimeter increase in axial length). CONCLUSIONS Normal macular thickness measurements using OCT in a large population-based sample of adult Chinese persons aged 30 to 85 years were generally thinner in the foveal and central macular areas than measurements reported in other populations. Age and axial length were positively correlated with macular thickness.

Rationale, Design, Methodology, and Baseline Data of a Population-Based Study in Rural China: The Handan Eye Study

Purpose: To describe the rationale, design, methodology and baseline characteristics of the Handan Eye Study (HES), a population-based study to determine the prevalence and impact of visual impairment and major ocular diseases in Chinese adults living in a rural region north China. Methods: Population-based, cross-sectional study. 6830 Han people aged 30 years and older from 13 villages of Yongnian County, Handan city, Hebei province, China were recruited. The interviews covered demographic, behavioral, and ocular risk factors as well as health-related and vision-related quality of life. Ocular examination included measurement of visual acuity (VA), intraocular pressure, anterior and posterior segment examinations, visual field testing, and anterior segment, fundus and optic disc photography/imaging. Physical examination included measurement of height and weight, blood pressure, electrocardiogram, fasting blood glucose, lipid levels, urea nitrogen and creatinine as well as tests of physical function including walking speed. Results: Of the 7557 individuals eligible for the Handan Eye Study (HES), 6830 (90.4%) subjects participated the study. The majority of participants were female (53.6%), the average (± standard deviation) age was 52.3 (± 12.3) years, and 100% were self-identified Han people. In contrast to the non-participants, those who participated were more likely to be female, elderly, married, and had more years of education (P < 0.05). Conclusion: The HES successfully examined over 90% of eligible Han Chinese adults aged 30 and older from a rural region of north China. Results from the HES will provide key information about the prevalence, risk factors, impact, and trends of ocular disease in rural regions of China.

Prevalence and Associations of Epiretinal Membranes in a Rural Chinese Adult Population: The Handan Eye Study

PURPOSE To determine the prevalence and association of epiretinal membranes (ERMs), as assessed by retinal photography and optical coherence tomography (OCT), in a Chinese population. METHODS The Handan Eye Study is a population-based study of eye disease in rural Chinese aged 30+ years. Eligible residents underwent a detailed ophthalmic examination including retinal photography and Stratus OCT. ERMs were defined by a combination of retinal photographs and OCT and classified as cellophane macular reflex (CMR) or preretinal macular fibrosis (PMF) based on retinal photographs characteristics. RESULTS Of the 6830 persons examined, 6565 (96.1%) had gradable retinal photographs and/or OCT. The mean age was 51.7 +/- 11.6 years. ERMs were present in 3.4% (95% CI: 2.9%-3.8%) of participants, bilateral in 20.3% of the cases. CMR was present in 2.2% and PMF in 0.7%, and ERMs were unclassified in 0.5% (detected by OCT only). ERM prevalence was similar in women and men (3.6% vs. 3.1%), strongly associated with increasing age (P for trend < 0.001). After adjustment for age and sex, primary ERM was associated positively with myopia (OR: 1.58, 95% CI: 1.12-2.23) and inversely with current smoking (OR: 0.61, 95% CI: 0.38-0.97, versus never smoked). Best corrected visual acuity was significantly worse in eyes with primary ERMs (mean LogMAR score lower by 0.07, 95% CI: 0.05-0.10) than eyes without ERMs, after adjustment for age, sex, and lens status. CONCLUSIONS ERMs affect 3.4% of the population 30+ years of age and living in rural China. Idiopathic ERMs were associated with myopia, decreased visual acuity, and inversely associated with smoking.

Prevalence of Age-Related Macular Degeneration in a Rural Chinese Population: The Handan Eye Study

PURPOSE To describe the prevalence of age-related degeneration (AMD) in a rural Chinese population and to assess its associations with age, gender, and smoking. DESIGN Population-based cross-sectional. PARTICIPANTS Persons aged 30+ years, recruited between October 2006 and October 2007, from Yongnian County, Handan, Hebei Province, China. METHODS All participants underwent a standardized interview and comprehensive eye examinations, including digital retinal photography of both eyes. Trained graders assessed the presence and severity of AMD lesions following the modified Wisconsin Age-related Maculopathy Grading System (WARMGS) used in the Blue Mountains Eye Study (BMES). Direct age standardization to the world population (year 2000) was performed to compare the prevalence across different populations. MAIN OUTCOME MEASURES AMD and WARMGS. RESULTS Of 6830 participates, fundus photographs were gradable for 6581 persons (96.4%), including 4049 aged 50+ years. Early and late AMD prevalence rates were 3.0% and 0.1%, respectively, among participants. The age-standardized prevalence rates among participants aged 50+ years were 4.7% and 0.2%, respectively. After controlling for age, men had a higher prevalence of early (3.9% vs. 2.3%, odds ratio [OR] 1.7; 95% confidence interval [CI], 1.3-2.2) and late AMD (0.1% vs. 0.03%; OR 3.5; CI, 0.4-33.4) compared with women. Older age (sex-adjusted OR 1.7; CI, 1.3-2.2 per decade of age) and current smoking (age-sex-adjusted OR 1.4; CI, 1.0-2.1) were significantly associated with early AMD prevalence. The proportion of current smokers was substantially higher in men (58.7%) than in women (0.3%). The attributable risk of early AMD from smoking among Chinese men was 24.2%. After controlling for current smoking, the excess prevalence of early AMD in men compared with women reduced by 50% (OR 1.4; 95% CI, 0.9-2.0). CONCLUSIONS The prevalence of early AMD in this rural Chinese sample was similar to white persons in the BMES and Asian Malays in the Singapore Malay Eye Study. Late AMD prevalence, however, was lower. Higher prevalence rates for early and late AMD in men compared with women were largely attributed to substantially higher proportions of smokers in rural Chinese men than in women.

Prevalence and causes of amblyopia in a rural adult population of Chinese the Handan Eye Study.

OBJECTIVE To determine the prevalence of and factors associated with amblyopia in a rural Chinese population. DESIGN Population-based, cross-sectional study. PARTICIPANTS Six thousand eight hundred thirty Han Chinese aged 30 years or more, recruited from Yongnian County, Handan, Hebei Province, China. METHODS Thirteen villages in the Yongnian County of Handan were selected randomly, and residents of these selected villages 30 years of age or older were invited to participate in the Handan Eye Study. Participants underwent a comprehensive eye examination, including standardized visual acuity (VA) tests using logarithm of the minimum angle of resolution charts. Prevalence rates were age- and gender-standardized to the 2000 China census. MAIN OUTCOME MEASURES The proportion of rural Chinese population aged 30 years or older with amblyopia. Unilateral amblyopia was diagnosed if best-corrected VA (BCVA) was 20/32 or worse in the amblyopic eye and was not attributable directly to any underlying structural abnormality of the eye or visual pathway. Bilateral amblyopia was diagnosed if BCVA was 20/32 or less in both eyes and if there was a history of form deprivation during the sensitive period of visual development, such as media opacities or high, uncorrected ametropia. RESULTS Amblyopia was diagnosed in 205 participants, with an age- and gender-adjusted prevalence of 2.8%. Of these, 1.7% were unilateral cases and 1.1% were bilateral cases. Underlying causes included anisometropia (67.3%), strabismus (5.4%), mixed strabismus and anisometropia (4.4%), visual deprivation (9.8%), astigmatism association (9.8%), and other (3.4%). Of the amblyopia cases, 47.6% were hypermetropic. CONCLUSIONS In this rural Chinese population, 2.8% of adults 30 to 80 years of age had amblyopia, a prevalence rate broadly consistent with that of most other studies. One third of the cases were bilateral, and anisometropia was the most common cause of this condition.

Eye care use among rural adults in China: the Handan Eye Study.

Abstract Purpose: To assess the use of eye care services in a rural population in North China and to analyze the factors associated with underuse of these services. Methods: In a cross-sectional population-based study, demographic, health and vision-related information including use of eye care services were determined during a face-to-face interview. A single visit to an eye care provider qualified as “use” of eye care services. Results: Of 6612 participants, 754 (11.4%, 95% confidence interval, CI, 8.7–14.1%) had used eye care services. The most common reason cited for not seeing an eye care provider was “no need” (n = 5754). Of the 5754 who thought that there was no need to see an ophthalmologist, 3458 (60.1%) were found to have one or more type of eye disease, including glaucoma (56, 1.0%), cataract (1056, 18.4%), age-related macular degeneration (AMD; 164, 2.9%) and refractive error (3048, 53.0%). Also, 74 (1.3%) and 409 (7.1%) of the 5754 participants had visual impairment (<20/60) according to best-corrected visual acuity and presenting visual acuity, respectively. In a multiple regression model, participants who had glaucoma (adjusted odds ratio, OR, 4.0, 95% CI 3.0–5.4), AMD (adjusted OR 1.6, 95% CI 1.2–2.3) or refractive error (adjusted OR 1.4, 95% CI 1.1–1.8), were more likely to visit an eye care provider. Conclusion: A high proportion of the Chinese rural population had never used eye care services although three fifths had eye diseases. Further efforts towards better education of the general population about common eye problems as well as increasing the number of ocular health providers would be necessary in future.

Prevalence and Causes of Low Vision and Blindness in a Rural Chinese Adult Population

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 A study of 6830 Han Chinese aged 30 years and older was conducted between October 2006 and October 2007 in rural Yongnian County in Handan, Northern China. METHODS Clustered samples of adults aged 30 years or more residing in 13 residential villages were selected randomly and were invited to participate the Handan Eye Study. Participants underwent a comprehensive eye examination, including standardized visual acuity (VA) tests using logarithm of the minimum angle resolution 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 was defined 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 WHO definitions. RESULTS Six thousand eight hundred thirty (90.4%) of 7577 eligible individuals participated in the study, and 6799 (89.7%) had 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 and older. Based on best-corrected visual acuity (BCVA), the corresponding prevalence of blindness was 0.5% and that of low vision was 1.0%. Blindness and low vision were strongly age related (P<0.05). Cataract was the predominant cause of presenting bilateral blindness (36.6%), whereas undercorrected refractive error was the predominant cause of presenting low vision (78.4%). After refractive correction, cataract became the first leading cause of blindness (41.9%), and low vision (48.2%), myopic retinopathy (16.1%), glaucoma (9.7%), and corneal opacity (9.7%) were other common causes of blindness 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 or more, is expected to be 12.4 million and 2.9 million, respectively. Predominant causes of low vision and blindness in China are treatable.

Original articlePrevalence and Causes of Low Vision and Blindness in a Rural Chinese Adult Population: The Handan Eye Study

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 A study of 6830 Han Chinese aged 30 years and older was conducted between October 2006 and October 2007 in rural Yongnian County in Handan, Northern China. METHODS Clustered samples of adults aged 30 years or more residing in 13 residential villages were selected randomly and were invited to participate the Handan Eye Study. Participants underwent a comprehensive eye examination, including standardized visual acuity (VA) tests using logarithm of the minimum angle resolution 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 was defined 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 WHO definitions. RESULTS Six thousand eight hundred thirty (90.4%) of 7577 eligible individuals participated in the study, and 6799 (89.7%) had 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 and older. Based on best-corrected visual acuity (BCVA), the corresponding prevalence of blindness was 0.5% and that of low vision was 1.0%. Blindness and low vision were strongly age related (P<0.05). Cataract was the predominant cause of presenting bilateral blindness (36.6%), whereas undercorrected refractive error was the predominant cause of presenting low vision (78.4%). After refractive correction, cataract became the first leading cause of blindness (41.9%), and low vision (48.2%), myopic retinopathy (16.1%), glaucoma (9.7%), and corneal opacity (9.7%) were other common causes of blindness 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 or more, is expected to be 12.4 million and 2.9 million, respectively. Predominant causes of low vision and blindness in China are treatable.