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Jose Manuel Gonzalez-Meijome, Rute J Macedo-de-Araújo, Ana I. Amorim-de-Sousa, Paulo Fernandes, Antonio Queiros; Change in myopia prevalence over 24 months in a school population from 6 to 13 years of age in Portugal. Invest. Ophthalmol. Vis. Sci. 2018;59(9):3384.
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© ARVO (1962-2015); The Authors (2016-present)
There is a global concern with myopia onset and progression in children due to the potential of reaching higher levels in adulthood with direct implications on ocular morbidity and blindness. Presently we do not have information about the prevalence of myopia and its progression in children and adolescents in Portugal and those are the goals of the present study.
One hundred and eight children with ages between 6 and 13 years of age (52% males) were evaluated in 2013 and again in 2015. Non-cycloplegic open-field autorefraction with WAM5500, Grand Seiko, Japan), axial length (AL) and mean keratometry (Kmean) with IOLMaster, Zeiss, Germany were measured five times and averaged. Study protocol was reviwed, approved and applied according to the Declaration of Helsinki. Refraction and biometric parameters between initial and final evaluation was compared with paired-sample T-test.
Average age at first examination was 9±2 years of age (range: 6 to 13) and 58.3% were under 10 years of age. Myopia was present in 9.3% at initial visit and in 17.6% at final visit. Hyperopia instead was present in 38% and 20.4% at initial and final visit, respectively. During the 2-year period, AL increased from 23.04±0.80 to 23.32±0.85mm (+0.28±0.32mm, p<0.001), SE changed in the negative direction from +0.21±1.02 to -0.03±1.07D (-0.24±0.65D, p=<0.001) and Kmean flattened from 7.75±0.26 to 7.80±0.27mm (+0.05±0.10, p<0.001). Changes in those who were myopes, emetropes and hyperopes at first visit were +0.36±0.25mm, +0.29±0.40mm and +0.24±0.21mm for AL, and +0.01±0.03mm, +0.03±0.08 and +0.07±0.13mm for Kmed, respectively. Boys showed a significantly flatter cornea (+0.20 mm, p<0.001) and longer eye (+0.68 mm, p<0.001) on average compared to girls but not different spherical or astigmatic refractive error (p>0.05).
Myopia prevalence almost double in a period of 2 years in this cohort of school children in Portugal. Axial length change in myopes support the increase in spherical equivalent refractive error, while in emmetropes and hyperopes, eye elongation seems to be more successfully counterbalanced by corneal flattening. Differences between boys and girls in axial length and corneal curvature suggest that emmetropization in boys worked better with corneal flattening of about 1.00D counterbalancing a larger axial elongation that would otherwise result in nearly 1.5 higher myopia.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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