Original Article
The Gobi Desert Children Eye Study
Abstract
Background: To summarize the design and findings of the Gobi Desert Children Eye Study.
Methods: The Gobi Desert Children Eye Study is a school-based cohort study. The baseline study was carried out in 2013, with 1,565 out of 1,911 eligible (81.9%) children with a mean age of 11.9±3.5 years (range: 6–21 years) as participants. The study was repeated in 2016 with 958 out of 1,334 eligible children (71.8%, or 61.2% of original participants) with a baseline mean age of 10.3±2.7 years (range: 6–16 years) participated. The participants completed a structured questionnaire and underwent comprehensive ocular examinations including cycloplegic refractometry, pneumotonometry, slit-lamp assisted biomicroscopy, fundus photography and optical coherence tomography.
Results: The mean refractive error at baseline in the worse eye was −1.38 diopter (D). In multivariate analysis, more myopic refractive errors were associated with older age (P<0.001; regression coefficient B: −0.26), female gender (P=0.005; B: −0.26), more myopic paternal refractive errors (P<0.001;B: 0.20), more myopic maternal refractive errors (P<0.001; B: 0.18) and fewer hours spent outdoors (P=0.038; B: 0.18). The prevalence of myopia, defined as refractive errors (spherical equivalent) of ≤−0.50 D in the worse eye was 60.0%±1.2%. The prevalence of high myopia (≤−6.00 D) was 2.9%±0.4% in the whole study population, and it was 9.9%±3.0% in 17-year-old. It was not associated with time spent outdoors (P=0.66). The 3-year cumulative incidence of myopia, defined as newly developed refractive error (spherical equivalent) of ≤−0.50 D and ≤−6.00 D in the worse eye during the 3-year follow-up period, was 52.6% and 4.5%, respectively. The mean change of refractive error from baseline was −0.77 and −0.71 D for the right and left eye respectively. The progression of myopia more than −1 diopter happened in 51.0% of participants with baseline myopia ≤−0.50 D. The incidence of myopia (≤−1.00 D) significantly increased with older age (P<0.001; B: 1.14), fewer outdoor activity hours (P=0.07, B: 0.66), higher body height (P=0.002, B: 1.02), more myopic paternal refractive error (P<0.02;B: 0.82), but was not significantly associated with gender (P=0.76), ethnicity (P=0.36), baseline intraocular pressure (P=0.86) and choroidal thickness (P=0.19). The mean subfoveal choroidal thickness (SFCT) was 282±49 µm. In multivariate analysis, thicker SFCT was associated (regression coefficient r: 0.38) with higher hyperopic refractive error (P<0.001; B: 0.31), younger age (P<0.001; B: −0.10), male gender (P=0.03; B: −0.05), higher corneal refractive power (P<0.001; B: 0.12), and non-Han Chinese ethnicity (P=0.03; B: 0.05).
Conclusions: Even in Western China, prevalence and incidence of myopia in school children is high. As in East China, low and medium myopia was associated with less time spent outdoors. High myopia was not significantly associated with outdoor time. The relatively high myopia prevalence in school children in China predicts a marked increase in vision-threatening high myopia in future elderly populations in China.
Methods: The Gobi Desert Children Eye Study is a school-based cohort study. The baseline study was carried out in 2013, with 1,565 out of 1,911 eligible (81.9%) children with a mean age of 11.9±3.5 years (range: 6–21 years) as participants. The study was repeated in 2016 with 958 out of 1,334 eligible children (71.8%, or 61.2% of original participants) with a baseline mean age of 10.3±2.7 years (range: 6–16 years) participated. The participants completed a structured questionnaire and underwent comprehensive ocular examinations including cycloplegic refractometry, pneumotonometry, slit-lamp assisted biomicroscopy, fundus photography and optical coherence tomography.
Results: The mean refractive error at baseline in the worse eye was −1.38 diopter (D). In multivariate analysis, more myopic refractive errors were associated with older age (P<0.001; regression coefficient B: −0.26), female gender (P=0.005; B: −0.26), more myopic paternal refractive errors (P<0.001;B: 0.20), more myopic maternal refractive errors (P<0.001; B: 0.18) and fewer hours spent outdoors (P=0.038; B: 0.18). The prevalence of myopia, defined as refractive errors (spherical equivalent) of ≤−0.50 D in the worse eye was 60.0%±1.2%. The prevalence of high myopia (≤−6.00 D) was 2.9%±0.4% in the whole study population, and it was 9.9%±3.0% in 17-year-old. It was not associated with time spent outdoors (P=0.66). The 3-year cumulative incidence of myopia, defined as newly developed refractive error (spherical equivalent) of ≤−0.50 D and ≤−6.00 D in the worse eye during the 3-year follow-up period, was 52.6% and 4.5%, respectively. The mean change of refractive error from baseline was −0.77 and −0.71 D for the right and left eye respectively. The progression of myopia more than −1 diopter happened in 51.0% of participants with baseline myopia ≤−0.50 D. The incidence of myopia (≤−1.00 D) significantly increased with older age (P<0.001; B: 1.14), fewer outdoor activity hours (P=0.07, B: 0.66), higher body height (P=0.002, B: 1.02), more myopic paternal refractive error (P<0.02;B: 0.82), but was not significantly associated with gender (P=0.76), ethnicity (P=0.36), baseline intraocular pressure (P=0.86) and choroidal thickness (P=0.19). The mean subfoveal choroidal thickness (SFCT) was 282±49 µm. In multivariate analysis, thicker SFCT was associated (regression coefficient r: 0.38) with higher hyperopic refractive error (P<0.001; B: 0.31), younger age (P<0.001; B: −0.10), male gender (P=0.03; B: −0.05), higher corneal refractive power (P<0.001; B: 0.12), and non-Han Chinese ethnicity (P=0.03; B: 0.05).
Conclusions: Even in Western China, prevalence and incidence of myopia in school children is high. As in East China, low and medium myopia was associated with less time spent outdoors. High myopia was not significantly associated with outdoor time. The relatively high myopia prevalence in school children in China predicts a marked increase in vision-threatening high myopia in future elderly populations in China.
