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Purpose Understanding the association of iris colour and myopia may provide further insights into the role of the wavelength of lights in the pathophysiology of myopia. We aim to assess the association of iris colour and myopia in a school-based sample of Chinese students. Methods Two thousand three hundred and forty-six Year 7 students from 10 middle schools (93.5% response rate) aged 13-14 years in Mojiang, a small county located in Southwestern China, participated in the study. We obtained standardised slit lamp photographs and developed a grading system assessing iris colour (higher grade denoting a darker iris). Refractive error was measured after cycloplegia using an autorefractor by optometrists or trained technicians. An IOLMaster () was used to measure ocular biometric parameters including axial length ( AL). Results Of all the study participants, 693 (29.5%) were affected by myopia with the prevalence estimates being higher in girls (36.8%; 95% confidence interval [ CI]: 34.0, 39.6) than in boys (22.8%; 95% CI: 20.4, 25.1) ( p < 0.001). After adjusting for gender, height, parental history of myopia, time spent on computer, time spent watching TV, time spent outdoors, and time spent reading and writing, participants with a darker iris colour tended to have a higher prevalence of myopia, a more myopic refraction and a longer AL. Dose-response relationships were observed in all regression models ( p for trend <0.05). Conclusions Darker iris colour was associated with more myopic refractive errors and longer ALs among Chinese school-aged children and this association was independent of other known myopia-related risk factors. [ABSTRACT FROM AUTHOR]

Purpose To determine the prevalence, types and awareness of glaucoma in a rural community in China and to examine possible ethnic variations. Methods The Yunnan Minority Eye Study was a multi-ethnic community-based eye survey using random cluster sampling strategies. 2133 Bai, 2205 Han and 2208 Yi Chinese aged 50 years or older participated in this study. Glaucoma including primary open-angle glaucoma ( POAG), primary angle-closure glaucoma ( PACG) and secondary glaucoma was defined based on the International Society of Geographical and Epidemiological Ophthalmology criteria. Results The overall age-standardized prevalence of all glaucoma was 2.6% (95% confidence interval [ CI]: 2.2-3.1%) in this population. It was 1.8% (95% CI: 1.1-1.9%) for POAG and 0.5% (95% CI: 0.9-1.6%) for PACG, respectively. Among 29 people with secondary glaucoma, 27 (93%) were blind in at least one eye. The presence of primary open-angle glaucoma was associated with male gender (odds ratio [ OR] = 2.94; comparing men with women), Yi ethnicity ( OR = 2.27; comparing Yi with Han people), higher IOP ( OR = 1.09 per mmHg increase), and the presence of myopia ( OR = 1.84). Of the 212 participants with glaucoma, only 38 (18%) were aware of the disease and had been diagnosed previously as having glaucoma or suspected glaucoma. Patients who were better educated tended to be aware of the disease. Conclusions Significant ethnic difference in the prevalence of POAG was observed in this study. The low awareness of glaucoma highlights the pressing need to increase public awareness of this potentially blinding condition in rural China. [ABSTRACT FROM AUTHOR]

Purpose We described the prevalence and associated factors of myopia and high myopia in school children of different ethnicities in a rural community in Yunnan province, China. Methods A total of 7681 (93.4%) primary and secondary school students aged 5-16 years in Mangshi participated in this study. Cycloplegic refraction was performed using an auto-refractor. Information regarding demographic factors, socioeconomic status and lifestyle-related exposures were collected using a questionnaire. Multivariate logistic regression models were fitted to estimate the risk factors for myopia and high myopia. Results The overall prevalence of myopia and high myopia was 39.1% (95% confidence interval [CI]: 38.0, 40.2) and 0.6% (95% CI: 0.4, 0.8) in this study. Myopia prevalence increased significantly with increasing age ( p for trend <0.001). Girls were more likely to have myopia compared with boys ( p < 0.001). In multivariate analysis, the presence of myopia was associated with increasing height (odds ratio [OR] = 1.02; 95% CI: 1.01, 1.03), computer use (OR = 1.17; 95% CI: 1.03, 1.32), having myopic father (OR = 1.56; 95% CI: 1.24, 1.94), having myopic mother (OR = 1.33; 95% CI: 1.08, 1.63), and increasing time on reading (OR = 1.18; 95% CI: 1.09, 1.28) after adjusting for age, sex and ethnicity. Conclusions Nowadays myopia but not high myopia is prevalent among school children in rural China. Significant ethnic differences in myopia prevalence were not observed. A significant 'cohort effect' of myopia previously observed in urban cities had occurred in rural communities in China. [ABSTRACT FROM AUTHOR]

Purpose To determine the prevalence and possible causes for reduced visual acuity ( VA) in preschool children in a metropolis in China. Methods A school-based paediatric eye survey including 5862 preschool children aged three to 6 years was conducted from 2011 to 2012 in Yuhuatai District, Nanjing, China, using an age-stratified random sampling procedure. Clinical examinations including ocular alignment, ocular motility, visual acuity, prism cover test, cycloplegic refraction, stereopsis screening, slit lamp examination and fundus examination were performed by trained study ophthalmologists and optometrists. Reduced VA was defined as presenting VA of worse than 0.30 log MAR (Snellen 6/12 or 20/40), for both better and worse eyes. Results 5667 (94.8%) children with complete VA data were included in the data analyses. Among them, 208 and 93 had reduced VA in the worse and better eye, respectively. Reduced VA was detected in 3.7% (95% confidence interval [ CI] 3.2%-4.2%) in the worse eye and 1.6% (95% CI 1.3%-2.0%) in the better eye. No significant age and gender differences in reduced VA were observed ( p > 0.05). Refractive errors and amblyopia were the principal causes for reduced VA in the worse eye which accounted for 66.8% and 32.7% of the total cases with reduced VA, respectively. Astigmatism and hyperopia were the major types of refractive errors causing reduced VA. Conclusions The burden of reduced VA in preschool children in China was similar to that of Asian children of similar ages in the United States. Uncorrected refractive error and amblyopia were the principal causes for reduced VA among preschoolers (aged three to 6 years) in China. [ABSTRACT FROM AUTHOR]

Purpose The association between myopia and cognitive dysfunction among elderly adults was assessed by applying a Propensity Score Matching ( PSM) approach. This is a statistical method which allows investigators to estimate causal treatment effects using observational or nonrandomised data. Methods The study was designed as a community-based cross-sectional study based on a Chinese cohort aged 60 years or older in China. Objective refraction was measured using an autorefractor and subjective refraction was used to refine vision, using the results of the objective refraction as the starting point. Myopia was defined as a spherical equivalent value of less than −0.50 dioptre (D) in the right eye. The Abbreviated Mental Test ( AMT) was used for cognitive assessment. The propensity scores for myopia were formulated using 13 potential confounders. We matched the propensity scores for subjects with and without myopia within a caliper of 0.01 of logit function of propensity scores. Results About 4123 elderly adults who successfully completed the AMT were included in this analysis. The odds ratio ( OR) of cognitive dysfunction for myopia before matching was 1.98 (95% confidence interval [ CI] 1.61, 2.44; p < 0.001). There were significant covariate imbalances between comparison groups and after propensity score matching, covariate imbalance was significantly reduced. After propensity score matching, the OR of cognitive dysfunction was marginally significant and the magnitude of association was reduced ( OR: 1.31 95% CI 1.00, 1.71; p = 0.05). Traditional multivariate logistic regression modelling found an OR of 1.52 (95% CI 1.23, 2.06; p < 0.001) after adjusting for the 13 potential confounders. Conclusions Myopia was associated with a higher prevalence of cognitive dysfunction among elderly Chinese aged 60 years or older in China. The PSM approach may be a useful method to address selection bias in observational studies when randomised trials cannot ethically be conducted. [ABSTRACT FROM AUTHOR]

Purpose To evaluate an incentive-based intervention to increase time spent outdoors among children in a 9-month cluster randomised controlled trial. Methods Two hundred and eighty-five children aged 6-12 years of age were randomised to the intervention ( n = 147) or control arm ( n = 138) in the Family incentive trial ( FIT). The FIT intervention comprised of targeted education on myopia and good eye care habits, structured weekend outdoor activities and incentives for children to increase their daily steps via pedometers. The main outcome measure was outdoor time, measured by the WHO questionnaire and a 1-week diary. Results Interim analysis at 6 months showed a significant increase in mean outdoor time per week in the intervention arm (14.75 h week−1) compared to the control arm (12.40 h week−1) as measured by the questionnaire ( p = 0.04). However, greater outdoor time was not statistically significant at the end of the trial (15.95 h week−1 vs 14.34 h in the control group ( p = 0.29). Conclusions There was an increase in outdoor time for children in the incentive-based physical activity outdoor program after 6 months but not at the end of the trial. Further larger school trials with better compliance with the intervention and longer duration could be conducted to evaluate clinical outcomes such as myopic shifts. [ABSTRACT FROM AUTHOR]

Citation information: Pan C-W, Ramamurthy D & Saw S-M. Worldwide prevalence and risk factors for myopia. Ophthalmic Physiol Opt 2012, 32, 3-16. doi: 10.1111/j.1475-1313.2011.00884.x Abstract Background: Myopia, the most common type of refractive error, is a complex trait including both genetic and environmental factors. Numerous studies have tried to elucidate the aetiology of myopia. However, the exact aetiology of myopia is still unclear. Purpose: To summarize the worldwide patterns and trends for the prevalence of myopia and to evaluate the risk factors for myopia in population-based studies. Recent findings: The prevalences of myopia vary across populations of different regions and ethnicities. In population-based studies on children, the prevalence of myopia has been reported to be higher in urban areas and Chinese ethnicity. The regional and racial difference is not so obvious in adult populations aged over 40 years. More time spent on near work, less time outdoors, higher educational level and parental history of myopia have been reported to increase the risk of myopia. Conclusions: Environmental factors play a crucial role in myopia development. The effect of gene-environment interaction on the aetiology of myopia is still controversial with inconsistent findings in different studies. A relatively hyperopic periphery can stimulate compensating eye growth in the centre. Longitudinal cohort studies or randomized clinical trials of community-based health behaviour interventions should be conducted to further clarify the aetiology of myopia. [ABSTRACT FROM AUTHOR]