Peripheral Defocus and Axial Eye Growth in the Bifocal Lenses In Nearsighted Kids (BLINK) Study

Abstract

Purpose : The BLINK Study was a 3-year randomized clinical trial that found +2.50 D add center-distance multifocal soft contact lenses (MFCLs) slowed myopia progression versus +1.50 D 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 ± 1.2 years). Children had myopia of -0.75 D to -5.00 D (most hyperopic meridian) and <1.00 D astigmatism at enrollment (mean ± SD spherical equivalent (M) = -2.39 ± 1.00 D). 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 myopic (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 < .001).

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 significant slowing of axial growth seen with MFCLs.

This is a 2021 ARVO Annual Meeting abstract.

 

Figure 1. Peripheral defocus with contact lenses. Error bars = SEM.