Peripheral Defocus, Pupil Size, and Axial Eye Growth in Children Wearing Soft Multifocal Contact Lenses in the BLINK Study

PURPOSE. The purpose of this study was to evaluate the relationship between peripheral defocus and pupil size on axial growth in children randomly assigned to wear either single vision contact lenses, +1.50 diopter (D), or +2.50 D addition multifocal contact lenses (MFCLs). METHODS. Children 7 to 11 years old with myopia (-0.75 to -5.00 D; spherical component) and <= 1.00 D astigmatism were enrolled. Autorefraction (horizontal meridian; right eye) was measured annually wearing contact lenses centrally and +/- 20 degrees, +/- 30 degrees, and +/- 40 degrees from the line of sight at near and distance. Photopic and mesopic pupil size were measured. The effects of peripheral defocus, treatment group, and pupil size on the 3-year change in axial length were modeled using multiple variables that evaluated defocus across the retina. RESULTS. Although several peripheral defocus variables were associated with slower axial growth with MFCLs, they were either no longer significant or not meaningfully associated with eye growth after the treatment group was included in the model. The treatment group assignment better explained the slower eye growth with +2.50 MFCLs than peripheral defocus. Photopic and mesopic pupil size did not modify eye growth with the +2.50 MFCL (all P >= 0.37). CONCLUSIONS. The optical signal causing slower axial elongation with +2.50 MFCLs is better explained by the lens type worn than by peripheral defocus. The signal might be something other than peripheral defocus, or there is not a linear dose-response relationship within treatment groups. We found no evidence to support pupil size as a criterion when deciding which myopic children to treat with MFCLs.