Longitudinal measures of peripheral optical quality in young children

To assess longitudinal changes in optical quality across the periphery (horizontal meridian, 60°) in young children who are at high (HR) or low risk (LR) of developing myopia, as well as a small subgroup of children who developed myopia over a 3-year time frame.

Aberrations were measured every 6 months in 92 children with functional emmetropia at baseline. Children were classified into HR or LR based on baseline refractive error and parental myopia. Zernike polynomials were calculated for 4 mm pupils, accounting for the elliptical shape of the pupil in the periphery. Various metrics were computed, including Strehl Ratios with only high-order aberrations (HO-SR). Primary spherical aberration (SA), horizontal coma and defocus were also analysed given their relevance in emmetropisation. The areas under the image quality metrics for various regions of interest were computed.

HO-SR were higher in children at HR and children with myopia, even when SA was removed from the Strehl Ratio (SR) calculation. SA was less positive in children at HR and children with myopia. Defocus was more negative in children at HR and children with myopia at all eccentricities and was even more negative when computed relative to the fovea, an effect that increased in the mid periphery. Relative peripheral defocus also became more negative over time in children at HR and children with myopia at the mid temporal retina. The other aberrations showed no significant changes in time overall.

This longitudinal study showed differences in HO-SR, SA and defocus in the central and near-peripheral retina (±20°) of young children at HR before they develop myopia compared with children at LR for myopia. The results may indicate these eccentricities are significant in providing signals for emmetropisation. The small changes noted over time may indicate that the differences are a cause of myopia development.