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Abstract
Purpose: To study on and off-axis wavefront aberration of eyes of children and to determine the relationship with refractive error development.
Methods: On and off-axis ocular aberrations of cyclopleged eyes of children (mostly 12 year olds) were measured and compared to data obtained from a group of mostly 6 year old children. Only data from the right eyes were analysed (pupil diameter=5 mm) and categorised into refractive error groups based on M . Differences in on and off-axis aberrations between refractive and ethnic groups were analysed using univariate and multivariate analyses of variance with adjustment for multiple comparisons. Off-axis refraction was analysed using skiagrams and mean relative spherical equivalent.
Results: Data from 1,636 12 year old children (mean age 12.6 ± 0.4 years) was analysed. Lower order aberrations were the largest and higher order aberrations contributed to only 25% of the wavefront. There were no differences in the amount of total higher orders between refractive groups. Of the individual higher orders, spherical aberration was greater in hyperopic eyes (0.07 ± 0.06 µm) in comparison to emmetropic and myopic eyes (0.05 ± 0.04 µm and 0.05 ± 0.04 µm) (p<0.001). Myopic eyes had more positive values of Z(3,-1) (p<0.05). Similar results were obtained for the 1,364 6 year old children (mean age 6.7 0.4 years). Despite East Asian children being more myopic than other ethnic groups (p<0.01), there were no differences in higher orders except for low hyperopic East Asian eyes presenting with higher levels of positive spherical aberrations (p<0.001). When compared to the fovea, off-axis myopic eyes had hyperopia (0.55 to 1.66 D) and emmetropes and hyperopes had myopia (0.10 to -2.00 D). Astigmatism and defocus were the dominant off-axis aberrations. The magnitude of higher order aberrations (mostly 3rd orders) increased with eccentricity but was similar across refractive error groups.
Conclusions: Myopic eyes do not have abnormal or excessive levels of on and off-axis higher order aberrations but had patterns of off-axis refraction that may be associated with progression. Considerable inter-subject variability in higher order aberrations was seen for all refractive groups. However, their magnitude was small and suggests that any impact on the optical quality of the eye is negligible.