JUL 25, 2011
The authors report the results of an early-phase trial to test whether a Dual-Focus (DF) soft contact lens, designed to present a clear retinal image while simultaneously presenting 2.00 D of sustained myopic retinal defocus during distance and near viewing, slows myopia progression in children. They found that not only was myopia progression slowed, but eye elongation was reduced significantly. At the same time, normal acuity and contrast sensitivity were maintained.
This prospective, investigator-masked study included 40 children, ages 11 to 14, with a mean spherical equivalent refraction of -2.71 D. They wore a DF lens in one randomly assigned eye and a single-vision distance (SVD) lens in the fellow eye for 10 months, with the lens assignment swapped between eyes for the following 10 months. The DF lenses had a central zone that corrected refractive error and concentric treatment zones that created 2.00 D of simultaneous myopic retinal defocus during distance and near viewing. The control SVD lens had the same parameters but without treatment zones.
During the first period of the study before the lens assignments were swapped, the mean change in SER with DF lenses (-0.44 ± 0.33 D) was less than with SVD lenses (-0.69 ± 0.38 D; P < 0.001). The mean increase in axial eye length was also less with DF lenses (0.11 ± 0.09 mm) than with SVD lenses (0.22 ± 0.10 mm; P < 0.001). In 70 percent of the children, myopia progression was reduced by 30 percent or more in the eye wearing the DF lens relative to the eye wearing the SVD lens. Similar reductions in myopia progression and axial eye elongation were also observed with DF lens wear during the second period, after the lens assignments were switched. Visual acuity and contrast sensitivity with DF lenses were not significantly different than with SVD lenses. Accommodation to a target at 40 cm was driven through the central distance-correction zone of the DF lens.
The authors say the data suggest that sustained myopic defocus, even when presented to the retina simultaneously with a clear image, can act to slow myopia progression without compromising visual function. They conclude that because DF lenses provide normal acuity and contrast sensitivity, they have potential as a relatively safe and effective form of refractive correction that can also retard the progression of myopia.