Nces in study design and methodology resulted in a large discrepancy. The Beijing Eye Study [24], including both rural and urban subjects aged 40 years or older, relied solely on retinal photographs, while the HandanPrevalence 
and Risk Factors of iERM in ShanghaiEye Study [25], including rural subjects aged 30 years or older, relied on retinal photographs and/or optical SPDB web coherence tomography (OCT). Therefore, further study of ERM in a Chinese urban population is necessary. Moreover, according to population-based studies, in addition to old age [4,7,8,22?5,26,28], which is a recognized risk factor for iERM, other possible risk factors, such as get Eledoisin female gender [26], refractive error [4,24,25,28], diabetes [4,8,27], and serum cholesterol [22], are inconsistently associated with iERM. Therefore, in Part I of our study (a population-based study), we aimed to describe the prevalence of iERM in a random sample of the resident population aged 60 years or older in Beixinjing Blocks, Shanghai, China, relied on retinal photographs. Meanwhile we examined risk factors associated with iERM, including ocular, systemic and socio-demographic characteristics. Previous clinical studies [29?1] concerning the risk factors associated with iERM have been susceptible to selection bias because the cases usually came from hospital patients, who were generally at the second or higher stage of iERM and had subjective symptoms. Thus, in Part II 
of our study (a case-control study), comparing the participants with vs. without iERM from Part I was performed to further study the differences between the two groups. We have studied some possible iERM risk factors in Part I, such as old age, gender and diabetes, so we carried out a blood biochemical test for the cases and controls as a supplementary evaluation. Partial or complete PVD has been found in 80 to 95 of eyes with iERM in large clinical studies [32?4], and it is likely that the association between iERM and PVD is universal. Therefore, B-mode ultrasound and OCT examinations were conducted to analyze the existence of PVD in eyes with or without iERM. Furthermore, there is some controversy about the association between refractive error and iERM [8,23?6], so we further examined the axial length, corneal curvature, refractive diopter, anterior chamber depth (ACD), and intraocular press (IOP) in cases and controls.Materials and Methods Study Design and PopulationBeixinjing Blocks, located in the northwest of Shanghai, was selected for the study because of its relatively stable population (43,253 in the 2000 census, and 8,153 aged 60 years or older) and representative demographic and socioeconomic characteristics. Beixinjing Blocks has mostly urban residents whose economic conditions could be classified as middle class in China: average per capita annual incomes among urban households are 36,230 yuan ( 5728 US) [35]. Moreover, Beixinjing Blocks has fairly complete health archives for residents and its coverage rate had reached 97.52 in 2001. This study protocol was approved by the Human Research and Ethics Committee of the 18204824 Shanghai First People’s Hospital, affiliated Shanghai Jiaotong University, and adhered to the tenets of the Declaration of Helsinki. Part I: Population-based study. Between November 2010 and April 2011, a population-based study of the prevalence of iERM was designed and performed in Beixinjing Blocks. 23115181 Random cluster sampling was used to select the study sample. Clusters were defined geographically us.Nces in study design and methodology resulted in a large discrepancy. The Beijing Eye Study [24], including both rural and urban subjects aged 40 years or older, relied solely on retinal photographs, while the HandanPrevalence and Risk Factors of iERM in ShanghaiEye Study [25], including rural subjects aged 30 years or older, relied on retinal photographs and/or optical coherence tomography (OCT). Therefore, further study of ERM in a Chinese urban population is necessary. Moreover, according to population-based studies, in addition to old age [4,7,8,22?5,26,28], which is a recognized risk factor for iERM, other possible risk factors, such as female gender [26], refractive error [4,24,25,28], diabetes [4,8,27], and serum cholesterol [22], are inconsistently associated with iERM. Therefore, in Part I of our study (a population-based study), we aimed to describe the prevalence of iERM in a random sample of the resident population aged 60 years or older in Beixinjing Blocks, Shanghai, China, relied on retinal photographs. Meanwhile we examined risk factors associated with iERM, including ocular, systemic and socio-demographic characteristics. Previous clinical studies [29?1] concerning the risk factors associated with iERM have been susceptible to selection bias because the cases usually came from hospital patients, who were generally at the second or higher stage of iERM and had subjective symptoms. Thus, in Part II of our study (a case-control study), comparing the participants with vs. without iERM from Part I was performed to further study the differences between the two groups. We have studied some possible iERM risk factors in Part I, such as old age, gender and diabetes, so we carried out a blood biochemical test for the cases and controls as a supplementary evaluation. Partial or complete PVD has been found in 80 to 95 of eyes with iERM in large clinical studies [32?4], and it is likely that the association between iERM and PVD is universal. Therefore, B-mode ultrasound and OCT examinations were conducted to analyze the existence of PVD in eyes with or without iERM. Furthermore, there is some controversy about the association between refractive error and iERM [8,23?6], so we further examined the axial length, corneal curvature, refractive diopter, anterior chamber depth (ACD), and intraocular press (IOP) in cases and controls.Materials and Methods Study Design and PopulationBeixinjing Blocks, located in the northwest of Shanghai, was selected for the study because of its relatively stable population (43,253 in the 2000 census, and 8,153 aged 60 years or older) and representative demographic and socioeconomic characteristics. Beixinjing Blocks has mostly urban residents whose economic conditions could be classified as middle class in China: average per capita annual incomes among urban households are 36,230 yuan ( 5728 US) [35]. Moreover, Beixinjing Blocks has fairly complete health archives for residents and its coverage rate had reached 97.52 in 2001. This study protocol was approved by the Human Research and Ethics Committee of the 18204824 Shanghai First People’s Hospital, affiliated Shanghai Jiaotong University, and adhered to the tenets of the Declaration of Helsinki. Part I: Population-based study. Between November 2010 and April 2011, a population-based study of the prevalence of iERM was designed and performed in Beixinjing Blocks. 23115181 Random cluster sampling was used to select the study sample. Clusters were defined geographically us.
