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Purpose: Parental rural-to-urban migration has a wide range of health effects on children's but its impact on children's refractive status remains unclear. We aim to examine whether parental rural-to-urban migration could influence the refractive status of their children in rural areas of China. Methods: Among the 2346 grade 7 students in the Mojiang Myopia Progression Study, information regarding parental migration was collected by questionnaires and was successfully obtained in 2105 participants. Refractive error was measured in diopters (D) with cycloplegia using an autorefractor and axial length (AL) was measured using an IOL Master. One-to-one nearest-neighbor matching techniques with a 0.01 caliper level were used to estimate the propensity score matching (PSM) models. Results: Among all the participants, 472 pairs (1 student with vs. 1 student without migrant parents) were successfully matched based on propensity scores. Students with migrant parents had a lower proportion of myopia (29.2% vs. 40.7%; P <.001) and more hyperopic refractions (−0.25D vs. −0.31D; P =.04) compared with those without. They also had shorter ALs (23.4 mm vs. 23.6 mm) but the difference was not significance (P =.18). In addition, students with migrant parents spent less time reading after school per day (0.87 vs. 1.01 hours; P =.01). Conclusions: Myopia is less prevalent among children with migrant parents compared with those without. This study indicated that living without parents might be a protect factor for myopia in Chinese school student via giving them less pressure on study. [ABSTRACT FROM AUTHOR]

Purpose: To examine the distribution and determinants of central corneal thickness (CCT) including birth weight and gestational age in a school-based samples of Grade 7 students in rural China. Methods: 2346 (93.5%) grade 7 students with a mean age of 13.8 years participated in the study. CCT was measured for both eyes using the LenStar LS900. Information regarding birth weight and gestational age was retrieved from the participants' delivery records. A linear regression model was established to examine the relationship of birth weight, gestational age and other factors with CCT. Results: The mean CCT in this population was 534.7 µm and boys had a greater CCT compared with girls (P =.06). CCT was positively related to axial length (r = 0.056) while negatively related to anterior chamber depth (r = −0.076) and corneal power (r = −0.105). In multivariate analyses, the cornea was 19.35µm thinner in individuals with low birth weight compared with those with normal. In addition, the cornea was 25.25µm thinner in prematurely born adolescents compared with full-term ones. The combined effect of birth weight and gestational age on CCT was not statistically significant (P for interaction = 0.12) Conclusions: Low birth weight and small gestational age are associated with thinner corneas in adolescence. This disparity across groups with different levels of birth parameters should be taken into account by future studies investigating CCT as risk factors or diagnostic tests for glaucoma. [ABSTRACT FROM AUTHOR]

Purpose: Observational studies have suggested a possible relationship between disordered sleep and myopia, but the association may be subject to selection biases. We aimed to minimize selection biases and assess the association by applying a propensity score matching (PSM) approach., Methods: The study was designed as a school-based cross-sectional study on a Chinese cohort aged 13-14 years in rural areas of China. The Chinese version of the Children's Sleep Habits Questionnaire was used for the measurement of sleep quality and a score of 41 or more was used to define the presence of disordered sleep. Each participant's refractive status was measured after cycloplegia using an autorefractor and myopia was defined as spherical equivalent <-0.50 D. The propensity scores for disordered sleep were formulated using nine potential confounders. We matched the propensity scores for subjects with and without disordered sleep within a caliper of 0.01 of logit function of propensity scores., Results: In this study, 474 pairs (1 subject with vs. 1 subject without disordered sleep) were successfully matched based on propensity scores. The odds ratio (OR) of myopia for disordered sleep before PSM reached conventional levels of statistical significance (OR: 1.43 95% confidence interval [CI] 1.05, 2.58, p = 0.01). After matching, the magnitude of association was reduced and the OR of myopia was not significant (OR: 1.54 95% CI 0.90, 2.57, p = 0.46)., Conclusions: At current stage, there are insufficient evidence indicating that disordered sleep could affect the development of myopia in adolescents.

Purpose: We aim to determine the association of the types of lamp for homework including incandescent lamp, fluorescent lamp, and light-emitting diode (LED) lamp with the prevalence of myopia in Chinese children., Methods: 2346 grade 7 students from ten middle schools (93.5% response rate) aged 13 to 14 years in Mojiang, a small county located in Southwestern China, participated in the study. Refractive error was measured with cycloplegia using an autorefractor by optometrists or trained technicians. An IOL Master was used to measure ocular biometric parameters including axial length (AL). Information regarding the types of lamp for homework af``ter schools was collected by questionnaires., 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 potential confounders such as gender, height, parental history of myopia, time on computer use, time on watching TV, time outdoors, and time on reading and writing, participants using LED lamps for homework had a more myopic refractive error and a longer AL compared with those using incandescent or fluorescent lamps. There were no significant differences in myopia prevalence between children using incandescent and fluorescent lamps for homework. The population attributable risk percentage for myopia associated with using LED lamps for homework after schools was 11.2%., Conclusions: Using LED lamps for homework after schools might contribute to the development of myopia among school-aged children.

Purpose: To determine the prevalence and associations of pterygium in a multiethnic adult population in rural China and to examine potential ethnic differences Methods: A total of 6418 adults (2133 ethnic Bai, 2130 ethnic Yi, and 2155 ethnic Han) aged 50 years or older participated in the study. Anterior segment examination was performed without pupil dilation using a slit lamp. Pterygium was defined as a raised fleshy triangular fibrovascular tissue growth of the conjunctiva encroaching onto a clear cornea., Results: Pterygium was least prevalent among adults of Yi ethnicity (29.5%) compared with Bai (39.0%, p < 0.001) or Han (39.5%, p < 0.001) ethnicities. Those of Bai ethnicity were most likely to be affected by severe pterygium (7.5%), while Yi were least likely to be affected (3.8%). Multivariate analysis revealed that increasing age (odds ratio, OR, 1.017), female sex (OR 1.53), lower educational level (OR 1.25), higher blood pressure levels (OR 1.002), and greater time spent outdoors per day (OR 1.09) were significantly associated with a higher prevalence of pterygium, while Yi ethnicity (OR 0.65, comparing Yi with Han) and wearing brimmed hats outdoors (OR 0.82) were protective factors., Conclusion: Ethnicity was significantly associated with prevalence of pterygium. Our findings may be applicable to many other countries located within the "pterygium belt" for health resource allocation among different ethnic groups.