Title: Peripheral Defocus and Axial Eye Growth in the Bifocal Lenses in Nearsighted Kids (BLINK) Study
Authors: David A. Berntsen (1), Anita T. Gostovic (1), Loraine T. Sinnott (2), Moriah A. Chandler (1), Juan Huang (3), Ann Morrison (2), Lisa A. Jones-Jordan (2), Jeffrey J. Walline (2), and Donald O. Mutti (2) for the BLINK Study group
1: College of Optometry, The University of Houston, TX
2: College of Optometry, The Ohio State University, Columbus, OH
3: School of Optometry, The University of Alabama at Birmingham, Birmingham, Alabama, United States
Reference: ARVO 2021 abstract and video presentation
The BLINK study found that +2.50 Add centre-distance multifocal contact lenses (MFCLs) slowed myopia progression but the +1.50 Add didn't. This leads to a dose-response hypothesis: a presumption that higher adds will produce a greater myopia control effect. In this study, the authors evaluated change in peripheral defocus with the MFCLs and found that:
- The +2.50 Add MFCLs created an average of just under 1.00D myopic shift at 40 degrees peripherally compared to single vision, during distance and near viewing
- The myopic shift in defocus with +2.50 Add MFCLs only explained about 15% of the reduction in axial length growth.
This indicates that a dose-response to peripheral defocus does not fully explain the myopia control efficacy of MFCLs - perhaps exceeding a threshold or other mechanisms are involved.
What does this mean for your clinical practice? The +2.50 Add MFCL has shown myopia control efficacy in the previously published BLINK study, although it is not regulatory indicated for slowing myopia progression. Using higher adds than +2.50 in attempt to achieve even stronger myopia control effect may have a very small but clinically insignificant impact.
Purpose: The BLINK Study was a 3-year randomised clinical trial that found +2.50D add centre-distance multifocal soft contact lenses (MFCLs) slowed myopia progression versus +1.50D add MFCLs and single vision contact lenses (SVCLs). In this analysis, we explore the relationship between peripheral defocus and axial growth.
Methods: 294 myopic children 7-11 years old (60% female) were enrolled (mean ± SD age = 10.3 ± 1.2years). Children had myopia of -0.75D to -5.00D (most hyperopic meridian) and <1.00D astigmatism at enrolment (mean ± SD spherical equivalent (M) = -2.39 ± 1.00D). Children were randomly assigned to one of three lenses: SVCL, +1.50 add MFCL, or +2.50 add MFCL. Autorefraction (horizontal meridian; right eye) was measured while wearing CLs centrally (line of sight) and ±20°, ±30°and ±40° from the line of sight while viewing a near target (30cm) and also at distance after cycloplegia. Each child’s defocus (M) profile at distance and near were fit using quadratic equations. Models of the first-year change in axial length (measured by optical biometry) were fit including the quadratic coefficient (Qc) for defocus at distance or near, central M, gender, study site, and age.
Results: After 1 year, mean axial growth was on average 0.13mm less in the +2.50 add group (p<.001) and 0.03mm less in the +1.50 add group (p = .11) versus SVCLs. Compared to SVCLs, peripheral defocus at distance was more myopia (less positive Qc) with MFCLs (Figure 1). At the 1-year visit, the average Qc in the +2.50 versus the SVCL group was .0005 D/degree2 less at distance and .0004 D/degree2 less at near. More myopic peripheral defocus at distance and at near in the +2.50 group was associated with less axial growth (distance: ß=31, or .016mm less axial growth, p=.005; near: ß=49, or .020mm less axial growth, p<0.01).
Conclusions: More myopic peripheral defocus at distance and near in children wearing +2.50 add MFCLs compared to SVCLs was associated with less axial growth in the BLINK Study, but not by a clinically meaningful amount. The small association suggests that a linear dose-response to peripheral defocus may not fully explain the effects of MFCLs on axial growth. Exceeding a threshold amount of peripheral myopic defocus or mechanisms other than peripheral defocus may cause the significantly slowing of axial growth seen with MFCLs.
Disclosures: David A. Bernsten, Bausch+Lomb (Code F (Financial Support)), Visioneering Technologies, Inc. (Code C (Consultant)); Anita T. Gostovic, Bausch+Lomb (Code F (Financial Support)); Loraine T. Sinnott, Bausch+Lomb (Code F (Financal Support)); Moriah A. Chandler, Bausch+Lomb (Code F (Financial Support)); Juan Huang, Bausch+Lomb (Code F (Financial Support)); Ann Morrison, Bausch+Lomb (Code F (Financial Support)); Lisa Jordan, Bausch+Lomb (Code F (Financial Support)); Jeffrey J. Walline, Bausch+Lomb (Code F (Financial Support)), SightGlass (Code C (Consultant)); Donald O. Mutti, Bausch+Lomb (Code F (Financial Support)), Welch Allyn (Code C (Consultant))
Ailsa Lane is a contact lens optician based in Kent, England. She is currently completing her Advanced Diploma In Contact Lens Practice with Honours, which has ignited her interest and skills in understanding scientific research and finding its translations to clinical practice.