Study design, rationale and methods for a population-based study of myopia in schoolchildren: the Myopia Investigation study in Taipei.

BACKGROUND: To describe the study design, rationale and methodology of the Myopia Investigation Study in Taipei (MIT). DESIGN: The MIT was a city-wide, population-based cohort study. PARTICIPANTS: Participants were grade 2 students (Fall 2013) of all 153 elementary schools in Taipei City. METHODS: The baseline data on the risk factors for myopia development was collected by parent-administered questionnaire surveys covering demographics, medical history, parental myopia, time spent on near work and outdoor activities, reading habits and eye care-seeking behaviour. Ocular examinations focused on the measurement of visual acuity (unaided and best-corrected) and refractive status (before and after cycloplegia), which will be carried out for the eligible schoolchildren biannually for 3 years consecutively. Once myopic children are identified, case manager-led telecoaching for health-care instructions and reminders will be delivered to parents or caregivers. MAIN OUTCOME MEASURES: To build a comprehensive database for prevalence, incidence and risk factors of early childhood myopia over a 3-year follow-up period. RESULTS: Of all 19 374 eight-year-old schoolchildren (10 210 [52.7%] boys) eligible for the MIT, 16 486 (85.1%) responded to the questionnaire, 12 019 (62.0%) were examined during the third quarter of 2013 and 11 590 (59.8%) (6267 [52.9%] boys) completed cycloplegic autorefraction on both eyes and were enrolled for further data analysis. There was no significant difference in terms of demographics between the analysed participants and all grade 2 students in Taipei City. CONCLUSIONS: Data from the MIT will provide population-based information concerning the prevalence, incidence and risk factors for myopia development among young schoolchildren in a metropolitan area of Taiwan.

Seasonal variation of refractive error change among young schoolchildren in a population-based cohort study in Taipei.

PURPOSE: To investigate the relationship between seasonal variation of daylight length and spherical equivalent (SE) progression among the schoolchildren participating in the Myopia Investigation Study in Taipei. METHODS: We used the first-year data from grade 2 schoolchildren who completed all the baseline and two follow-up examinations (n=6790). There were two 6-month intervals between visits over winter and summer, respectively. For each interval, we calculated average daily daylight length using data from Taiwan's Central Weather Bureau and measured 6-month SE progression rate based on right eye cycloplegic autorefraction data. The midpoint month was defined as the month midway between two consecutive visits. RESULTS: By the midpoint month, average daily daylight length was the shortest in December (671±7 min/day) and the longest (785±7 min/day) in June, and SE progression rate was the fastest (-0.23±0.48 D) in December and the slowest (-0.17±0.51 D) in June. Significant variation of SE progression rate with season can be observed only among the schoolchildren (n=1905) whose midpoint months for the winter and summer intervals were December and June (winter rate, -0.25±0.47 D; summer rate, -0.17±0.49 D; p<0.001). Of those, the summer progression rate was approximately 80%, 65% and 61.5% of that measured in winter for myopic (p=0.252), emmetropic (p=0.012) and hyperopic (p=0.012) schoolchildren, respectively. CONCLUSION: Our data demonstrate a seasonal variation of minus shift in refractive error among Taipei schoolchildren who had significant daytime fluctuation during the 1-year follow-up. Of those, non-myopic children had significant and more pronounced variation of SE progression than myopic children.

Prevalence and association of refractive anisometropia with near work habits among young schoolchildren: The evidence from a population-based study.

BACKGROUND: Lifestyle behaviour may play a role in refractive error among children, but the association between near work habits and refractive anisometropia remains unclear. METHODS: We estimated the prevalence of refractive anisometropia and examined its association with near work activities among 23,114 children in the Myopia Investigation Study in Taipei who were grade 2 elementary school students at baseline in 2013 and 2014. Baseline data on demographics, medical history, parental history and near work habits were collected by parent-administered questionnaire survey. Refractive status was determined by cycloplegic autorefraction. Refractive anisometropia was defined as the spherical equivalent difference ≥ 1.0 diopter between eyes. RESULTS: The prevalence of refractive anisometropia was 5.3% (95% confidence interval [CI], 5.0% to 5.6%). The prevalence and severity of refractive anisometropia increased with both myopic and hyperopic refractive error. Multivariate logistic regression analysis revealed that refractive anisometropia was significantly associated with myopia (odds ratio [OR], 2.98; 95% CI, 2.53-3.51), hyperopia (OR, 2.37; 95% CI, 1.98-2.83), degree of astigmatism (OR, 1.005; 95% CI, 1.005-1.006), amblyopia (OR, 2.54; 95% CI, 2.06-3.12), male gender (OR, 0.88; 95% CI, 0.78-0.99) and senior high school level of maternal education (OR, 0.69; 95% CI, 0.52-0.92). Though anisometropic children were more likely to spend more time on near work (crude OR, 1.15; 95% CI, 1.02-1.29) and to have less eye-to-object distance in doing near work (crude OR, 1.15; 95% CI, 1.01-1.30), these associations became insignificant after additional adjustment for ocular, demographic and parental factors. CONCLUSIONS: The present study provides large-scale, population-based evidence showing no independent association between refractive anisometropia and near work habits, though myopia is associated with refractive anisometropia.

Risk factors for myopia progression in second-grade primary school children in Taipei: a population-based cohort study.

PURPOSE: To evaluate the 1-year progression of myopia and associated risk factors in second-grade primary school children. METHODS: The myopia investigation study in Taipei provided semiannual visual acuity testing and cycloplegic refraction for all second-grade primary school children (mean age: 7.49 years) in Taipei who provided parental consent. A questionnaire was distributed to the participants' parents before the first and third examinations. We evaluated 1-year follow-up data for children noted to have myopia on the first examination. Multinomial logistic regression models were applied to assess risk factors associated with myopia progression. Myopia progression was categorised, based on the change in spherical equivalent (ΔSE) over 1 year, as slow (ΔSE>-0.5 dioptres (D)), moderate (-1.0 D<ΔSE≤-0.5 D) or fast (ΔSE≤-1.0 D). Of the 4214 myopic children, data were analysed for 3256 (77.3%) who completed the 1-year follow-up evaluation. RESULTS: The baseline SE was -1.43±1.1 D. The average ΔSE was -0.42±0.85 D, with 46.96%, 28.50% and 24.54% of the study subjects showing slow, moderate and fast myopia progression, respectively. When compared with slow myopia progression, fast myopia progression was associated with a greater myopic SE at baseline (OR: 0.67, 95% CI: 0.61 to 0.72) and a shorter eye-object distance when doing near work (OR: 1.45, 95% CI: 1.18 to 1.78). More outdoor activity time and self-reported cycloplegic treatment were not associated with slow myopia progression. CONCLUSIONS: Children with fast annual myopia progression were more myopic at baseline and had a shorter reading distance. Our study results highlight the importance of having children keep a proper reading distance.

Myopia Development Among Young Schoolchildren: The Myopia Investigation Study in Taipei.

Purpose: To investigate the annual incidence of myopia and associated factors among young schoolchildren in Taipei City. Methods: The Myopia Investigation Study in Taipei was a citywide, population-based cohort study. During the fall 2013 semester (baseline), a total of 11,590 grade 2 schoolchildren completed ocular examination and were included for further analysis. A parent-completed questionnaire was administered to collect data on risk factors for myopia development. Follow-up visits were arranged biannually over 3 years. The first-year results are reported here. Schoolchildren who were emmetropic/hyperopic at baseline and had myopia (spherical equivalent ≤ -0.5 diopters) in either eye at follow-up were identified as having incident myopia. Results: Among 7376 baseline nonmyopic participants, 6794 (92.1%) were examined during the first-year follow-up, and 1856 (25.2%) with incident myopia were identified. The incidence density of myopia was 31.7 (95% confidence interval [CI]: 30.6-32.8) per 100 person-years. Cox hazard proportional regression analysis revealed that participants who were emmetropic at baseline (hazards ratio [HR]: 19.37; 95% CI: 4.84-77.57), who had two myopic parents (HR: 1.21; 95% CI: 1.04-1.42), and who spent ≥5 hours every week on after-school tutoring programs (HR: 1.12; 95% CI: 1.02-1.22) had greater risk for incident myopia. By contrast, protective factors included suburban area of residence (HR: 0.91; 95% CI: 0.83-1.00) and spending ≥30 minutes outdoors after school every weekday (HR: 0.90; 95% CI: 0.82-0.99). Conclusions: This study provides population-based data on the annual incidence of myopia among Taiwanese schoolchildren, and found that baseline refractive status, parental myopia, area of residence, time outdoors after school on weekdays, and time spent on after-school tutoring programs are associated with risk of new-onset myopia.