Dual Focus Contact Lenses induce Myopic Defocus in Children during Near Viewing

Abstract

Purpose : Hyperopic defocus can accelerate eye growth in young eyes. Conversely, introduction of myopic defocus can slow eye growth and may counteract the grow signal from simultaneously present hyperopic defocus. Dual focus (DF) lenses for myopia control in children are designed to introduce myopic defocus. This study examined the optical impact of a DF contact lens during near viewing in a sample of children being treated with a DF lens.

Methods : Seventeen myopic children (14 to 18 years, mean ± SD: 16.61 ± 1.63 years) who had completed 3 or 6 years of treatment with a DF lens (MiSight 1 day, CooperVision, Inc., Pleasanton, CA) were fit bilaterally with a DF and a single vision (SV) contact lens (Proclear 1 day, CooperVision, Inc., Pleasanton, CA). Wavefront measurements along the visual axis of the right eye were acquired using a pyramidal aberrometer (Osiris, CSO, Italy) while subjects accommodated binocularly to high contrast letter stimuli (20/40 equivalent) at 6 target vergences (-0.25D, -1D to -5D in 1D steps). Wavefront error data were used to develop pupil maps of refractive error with each lens type.

Results : During near viewing, children fit with SV accommodated to achieve approximate focus in the pupil center but experienced up to 2D of hyperopic defocus in the pupil margins due to increasing levels of negative spherical aberration (C₄⁰ changed from -0.27μm at distance to -0.76μm at near) and accommodative lag. With DF, children accommodated similarly achieving approximate focus in the pupil center. The +2D myopic defocus of the DF lens was sufficient to shift the mean defocus in the treatment zone from hyperopia (+0.75D) to myopia (-1.00D) at near (50 cm to 25 cm). The DF lens reduced the % of hyperopic defocus (≥ +0.75D) in the foveal image from 50% to 28% over these target distances leading to an increase in myopic defocus (≤ -0.50D) from 18% to 40%. Lowering the criteria for defocus to > ±0.25D, increased the % of defocused light (65% to 45% for hyperopia and 24% to 47% for myopia), but the shift towards myopic defocus created by the DF lens remained.

Conclusions : The DF contact lens did not alter the accommodative behavior of children. The +2D myopic defocus in the treatment zones successfully removed hyperopic defocus and introduced myopic defocus in the foveal image. These results are consistent with the hypothesis that myopia control with this DF design is achieved by the added myopic defocus.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.