May 08, 2013
Effect of Day Length on Eye Growth, Myopia Progression, and Change of Corneal Power in Myopic Children
Dongmei Cui, MD, PhD, Klaus Trier, MD, Søren Munk Ribel-Madsen, MSc, PhD
Because of the northern location of Denmark, the length of the day over the year varies from 7 to 17.5 hours. Experimental and clinical results suggest that the development of myopia may be related to ambient light exposure. The purpose of current study was to investigate whether axial eye growth, myopia progression, or corneal power change in Danish myopic children varies with the length of the day.
Two hundred thirty-five children 8 to 14 years of age found to have myopia during screening for a clinical trial (ClinicalTrial.gov identifier, NCT00263471; accessed December 6, 2005). All children found to have any value of spherical equivalent that was myopic (<0 diopters [D]) at the first of 2 visits were included.
Cycloplegic refraction was measured using an autorefractor, axial eye length, and corneal power using an automatic combined noncontact partial coherence interferometer and keratometer. The accumulated number of daylight hours during the measurement period was calculated for each participant using an astronomical table.
Main Outcome Measures
Change over 6 months in axial length, refraction, and corneal power.
Accumulated hours of daylight ranged from 1660 to 2804 hours. Significant correlations were found between hours of daylight and eye elongation (P = 0.00), myopia progression (P = 0.01), and corneal power change (P = 0.00). In children with an average of 2782±19 hours of daylight, axial eye growth was 0.12±0.09 mm, myopia progression was 0.26±0.27 D, and corneal power change was 0.05±0.10 D per 6 months, whereas in children with an average of 1681±24 hours of daylight, axial eye growth was 0.19±0.10 mm, myopia progression was 0.32±0.27 D, and corneal power change was −0.04±0.08 D per 6 months.
Eye elongation and myopia progression seem to decrease in periods with longer days and to increase in periods with shorter days. Children should be encouraged to spend more time outside during daytime to prevent myopia.
Outdoor Activity during Class Recess Reduces Myopia Onset and Progression in School Children
Pei-Chang Wu, MD, PhD, , Chia-Ling Tsai, BDS, MS, Hsiang-Lin Wu, BS
The aim of this study was to investigate the effect of outdoor activity during class recess on myopia changes among elementary school students in a suburban area of Taiwan.
Prospective, comparative, consecutive, interventional study.
Elementary school students 7 to 11 years of age recruited from 2 nearby schools located in a suburban area of southern Taiwan.
The children of one school participated in the interventions, whereas those from the other school served as the control group. The interventions consisted of performing a recess outside the classroom (ROC) program that encouraged children to go outside for outdoor activities during recess. The control school did not have any special programs during recess.
Main Outcome Measures
Data were obtained by means of a parent questionnaire and ocular evaluations that included axial length and cycloplegic autorefraction at the beginning and after 1 year.
Five hundred seventy-one students were recruited for this study, of whom 333 students participated in the interventional program, and 238 students were in the control school. At the beginning of the study, there were no significant differences between these 2 schools with regard to age, gender, baseline refraction, and myopia prevalence (47.75% vs. 49.16%). After 1 year, new onset of myopia was significantly lower in the ROC group than in the control group (8.41% vs. 17.65%; P<0.001). There was also significantly lower myopic shift in the ROC group compared with the control group (−0.25 diopter [D]/year vs. −0.38 D/year; P = 0.029). The multivariate analysis demonstrated that the variables of intervention of the ROC program and higher school year proved to be a protective factor against myopia shift in nonmyopic subjects (P = 0.020 and P = 0.017, respectively). For myopic subjects, school year was the only variable significantly associated with myopia progression (P = 0.006).
Outdoor activities during class recess in school have a significant effect on myopia onset and myopic shift. Such activities have a prominent effect on the control of myopia shift, especially in nonmyopic children
Body Stature Growth Trajectories during Childhood and the Development of Myopia
Kate Northstone, PhD, Jeremy A. Guggenheim, PhD, Laura D. Howe, PhD, Kate Tilling, PhD, , Lavinia Paternoster, PhD, John P. Kemp, MSc, George McMahon, PhD, Cathy Williams, PhD
Stature at a particular age can be considered the cumulative result of growth during a number of preceding growth trajectory periods. We investigated whether height and weight growth trajectories from birth to age 10 years were related to refractive error at ages 11 and 15 years, and eye size at age 15 years.
Prospective analysis in a birth cohort.
Children participating in the Avon Longitudinal Study of Parents and Children (ALSPAC) U.K. birth cohort (minimum N = 2676).
Growth trajectories between birth and 10 years were modeled from a series of height and weight measurements (N = 6815). Refractive error was assessed by noncycloplegic autorefraction at ages 11 and 15 years (minimum N = 4737). Axial length (AXL) and radius of corneal curvature were measured with an IOLMaster (Carl Zeiss Meditec, Welwyn Garden City, U.K.) at age 15 years (minimum N = 2676). Growth trajectories and an allelic score for 180 genetic variants associated with adult height were tested for association with refractive error and eye size.
Main Outcome Measures
Noncycloplegic autorefraction at ages 11 and 15 years, and AXL and corneal curvature at age 15 years.
Height growth trajectory during the linear phase between 2.5 and 10 years was negatively associated with refractive error at 11 and 15 years (P<0.001), but explained <0.5% of intersubject variation. Height and weight growth trajectories, especially shortly after birth, were positively associated with AXL and corneal curvature (P<0.001), predicting 1% to 5% of trait variation. Height growth after 2.5 years was not associated with corneal curvature, whereas the association with AXL continued up to 10 years. The height allelic score was associated with corneal curvature (P = 0.03) but not with refractive error or AXL.
Up to the age of 10 years, shared growth mechanisms contribute to scaling of eye and body size but minimally to the development of myopia.
The author(s) have no proprietary or commercial interest in any materials discussed in this article.