Axial length change and its relationship with baseline choroidal thickness - a five-year longitudinal study in Danish adolescents: the CCC2000 eye study

BackgroundMyopic eyes are longer than nonmyopic eyes and have thinner choroids. The purpose of present study was to investigate whether a thinner subfoveal choroid at 11years of age predicted axial eye elongation and myopia during adolescence.MethodsLongitudinal, population-based observational study. Axial length was measured using an interferometric device and choroidal thickness was measured by spectral-domain optical coherence tomography. Myopia was defined as non-cycloplegic subjective spherical equivalent refraction <= -0.50 diopters.ResultsRight eyes of 714 children (317 boys) were examined at age (median (IQR)) 11.5 (0.6) years and 16.6 (0.3) years during which axial length (median (IQR)) increased by 243 (202) mu m in eyes without myopia (n=630) at baseline compared with 454 (549) mu m in eyes with myopia (n=84) at baseline, p<0.0001. A thicker baseline subfoveal choroid was associated with increased five-year axial elongation after adjustment for baseline axial length in nonmyopic eyes (=27 mu m/100 mu m, 95%CI 6 to 48, p=0.011) but not in myopic eyes (p=0.34). Subfoveal choroidal thickness at 11years of age did not predict incident myopia at 16years of age (p=0.11). Longer baseline axial length was associated with greater five-year axial elongation in both myopic (beta =196 mu m/mm, 95%CI 127 to 265, p<0.0001) and nonmyopic eyes (=28 mu m/mm, 95%CI 7 to 49, p=0.0085) and the odds for incident myopia increased with 1.57 (95%CI 1.18 to 2.09, p=0.0020) per mm longer axial length at baseline.ConclusionA thin subfoveal choroid at age 11years did not predict axial eye elongation and incident myopia from age 11 to 16years. A longer eye at age 11years was associated with greater subsequent axial eye elongation and with increased risk of incident myopia at age 16years.