Dual focus contact lenses and near viewing

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

Authors: Dawn Meyer (1), Viswa Ramasubramanian (1), Nicola S Logan (2), Susie Jones (2), Matt Jaskulski (1), Martin Rickert (1), Arthur Bradley (3), Baskar Arumugam (3), Paul Chamberlain (3), Pete S Kollbaum (1)

1. School of Optometry, Indiana University Bloomington, Bloomington, Indiana, United States
2. School of Optometry, Aston University, Birmingham, Birmingham, United Kingdom
3. Coopervision Inc, Pleasanton, California, United States

Date: June 2022

Reference: Meyer D, Ramasubramanian V, Logan NS, Jones S, Jaskulski M, Rickert M, Bradley A, Arumugam B, Chamberlain P, Kollbaum PS. Dual Focus Contact Lenses induce Myopic Defocus in Children during Near Viewing. Invest. Ophthalmol. Vis. Sci. 2022;63(7):1437 - F0395. [Link to abstract]

It is well established that hyperopic defocus can act as a stimulus for eye growth in young eyes, while myopic defocus may generate signals to inhibit eye growth. This has been postulated as a theory for the myopia control efficacy of contact lenses and glasses that use positive lenses to induce hyperopic defocus. 

This abstract examined the optical impact of a dual focus contact lens during near viewing in a sample of children being treated with a dual focus lens.

Myopic children aged 14-18 years (n=17) who had completed 3 or 6 years of wearing a dual focus contact lens (MiSight 1 day) were fit bilaterally with a dual focus and a single vision contact lens. A pyramidal aberrometer was used to obtain wavefront measurements along the visual axis while subjects accommodated bilaterally to high contrast letter stimuli (20/40 equivalent) at 6 target vergences (viewing distances from 4m to 20cm). 

Results:

• During near viewing, children fit with single vision contact lenses accommodated to achieve approximate focus in the pupil centre but experienced up to 2D of hyperopic defocus in the pupil margin (due to increasing levels of negative spherical aberration and accommodative lag)
• With dual focus contact lenses, children accommodated similarly in the pupil centre. However, the +2D myopic defocus shifted the mean defocus in the treatment zone from hyperopia (+0.75D) to myopia (-1.00D) at near (50cm to 20cm)
• The dual focus lens reduced the percentage of hyperopic defocus in the foveal region from 50% to 28% over these target distances. This lead to an increase in myopic defocus from 18% to 40%
• This indicates that the +2D myopic defocus in the treatment zones successfully removed hyperopic defocus and introduced myopic defocus in the foveal image. The dual focus lens did not alter accommodative behaviour compared to single vision.

Clinically, this this study can be used to facilitate discussions with patients and their parents:

• Firstly, it indicates that dual focus contact lenses do not alter the accommodative behaviour of teens aged 14-18 years.
• Secondly, it provides us with more information around the likely mechanism for which dual focus contact lenses slow myopia progression.

These results support the hypothesis that myopic control with dual focus contact lenses is achieved by the added myopic defocus. Further research could be conducted to investigate if the optical behaivour of children (ie the peripheral defocus) can be used to predict their relative success with dual focus lenses as a method of myopia control.

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

Authors: Dawn Meyer, Viswa Ramasubramanian, Nicola S Logan, Susie Jones, Matt Jaskulski, Martin Rickert, Arthur Bradley, Baskar Arumugam, Paul Chamberlain, Pete S Kollbaum

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.

Conclusion: 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.

[Link to abstract]