The Bifocal Lens Inhibition of Myopia Progression (BLIMP) Study is a two year study comparing the progression of myopia in forty children ages eight to eleven fit in bifocal soft contact lenses to age- and gender-matched children fit in spherical soft contact lenses in the Adolescent and Child Health Initiative to Encourage Vision Empowerment (ACHIEVE) Study. Few studies have explored bifocal soft contact lenses for myopia progression inhibition, and no full studies have been published in peer-reviewed publications. This thesis only includes the one year data of twenty eight children, and all data are confidential.
Distance center bifocal soft contact lenses are being used in this study. This is to allow accurate focus of light on the fovea for clear vision while providing peripheral retinal myopic blur that animal studies have shown to change eye growth patterns. Refractive quality of life assessment took place before subjects were fit in contacts and at every follow-up visit. Their refractive quality of life improved and was equivalent to that of children fit in spherical soft contact lenses in the ACHIEVE Study. Previous studies have explored lined bifocal spectacles, no-line bifocal spectacle lenses, and bifocal soft contact lenses as myopia progression inhibition methods assuming accommodative error or effort is part of what drives myopia progression.
We fit twenty eight pediatric subjects in bifocal soft contact lenses and followed them for a period of one year. We measured refractive and biometric data at baseline and one year. The same data were measured in a historical control group of twenty eight age- and gender-matched spherical soft contact lens wearers.
Our data suggest that the children fit in bifocal soft contact lenses had less increase in their myopia over a year than the children who wore single vision spectacles (SVLs). The average (±SD) rate of progression of the spherical equivalent refractive error of the soft bifocal contact lens subjects was -0.39 ± 0.53 D for the right eye and -0.40 ± 0.39 D for the left eye. The rate of progression of the spherical equivalent refractive error of the soft spherical contact lens subjects was -0.60 ± 0.32 D for the right eye and -0.54 ± 0.34 D for the left eye. These progressions were not significantly different (Student’s t-test, p = 0.08 and p = 0.15). The axial length data were not consistent with the refractive error data. The axial length of the soft bifocal contact lens subjects’ eyes increased by 0.18 ± 0.22 mm in the right eye and by 0.11 ± 0.23 mm in the left eye. The axial length of the soft spherical contact lens subjects’ eyes increased by 0.23 ± 0.17 mm in axial elongation of the right eye between soft bifocal and soft spherical contact lens wearers (Student’s t-test, p = 0.329), but the left eyes of the spherical soft contact lens wearers grew significantly more than the left eyes of the bifocal soft contact lens wearers (Student’s t-test, p = 0.004).
Our study has not found a significant decrease in progression of myopia in children fit in bifocal soft contact lenses at this sample size.