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Karen M. Breslin, K J. Saunders, E O'Donoghue, J McClelland; Axial Length And Refractive Error Prior To And After The Onset Of Myopia. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2501.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate axial length (AL) and refractive error prior to and after the onset of myopia in childhood.
The Northern Ireland Childhood Errors of Refraction (NICER) study used stratified random sampling to identify a representative group of children in which to investigate prevalence of refractive error. Initially 399 6-7 year-old-children were examined. After 36±3 months these children were invited for repeat examination (aged 9-10 yrs). Following parental and child consent, the participants were examined at school. Participants’ refractive errors were determined by cycloplegic autorefraction (1 drop 1% cyclopentolate HCl) using the Shin-Nippon SRW-500 Autorefractor. Axial length was measured using the Zeiss IOLMaster.Myopia was defined as at least -0.75 D in each meridian. The change in refractive error was defined as the difference in mean spherical equivalent refraction (SER) between the initial study and repeat examination. The change in AL was defined as the difference in average AL measurement between the initial study and repeat examination. Analyses were performed on right eye data using non-parametric Mann-Whitney tests with p <0.05 indicating statistical significance.
90% (n=358) of subjects in the initial study were contactable. Of these 84% (n=301) participated in repeat examination. Data are presented for 297 white participants (99%) of whom 14 became myopic. Participants who became myopic had a statistically significantly greater shift in SER compared with those who remained non-myopic (median=-1.25, IQR -1.50 to -0.875; median=-0.375, IQR -0.625 to 0.00 respectively). The former also had a statistically significantly greater shift in AL (median=0.94, IQR 0.79 to 1.17; median=0.48, IQR 0.39 to 0.59 respectively). Prior to the onset of myopia, participants who became myopic had statistically significantly longer AL (median= 23.07, IQR 22.61 to 23.59) compared with their peers (median=22.53, IQR 22.02 to 23.05).
Although most children demonstrate increasing AL and a decreasing SER between 6-7 and 9-10 years of age, those who become myopic during this period show the greater change. These data support previous work and suggest that longer ALs in the early school years may predict future myopia.
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