Dr. John R. Phillips and Dr. Nicola S. Anstice at the University of Auckland explain in Ophthalmology online January 27 that while optical correction restores visual acuity, it does not stop enlargement of the myopic eye. “Thus, children with myopia remain at increased risk of ocular disease later in life.”
Evidence from animal and human studies indicate that retinal defocus — with the plane of focus in front to the retina — reduces axial eye growth, but at the cost of poor acuity.
The researchers developed a dual-focus soft contact lens with a central zone that corrects refractive error and presents a clear retinal image, while concentric treatment zones on the lens simultaneously create sustained retinal defocus peripherally.
To see if wearing the lens would slow myopia progression, Drs. Phillips and Anstice had 40 affected children wear the dual-focus lens in one eye and a single vision distance lens in the other for 10 months, and then switch lens assignment between eyes for a second 10-month period. The children were between 11 and 14 years of age, with a mean spherical equivalent refraction (SER) of -2.71 diopters.
During the first period, the mean change in SER was -0.44 diopters in the eyes with dual-focus lens compared with -0.69 diopters with the single-focus lens. Corresponding mean increases in axial length were 0.11 mm and 0.22 mm, according to the report.
“In 70% of the children, myopia progression was reduced by 30% or more in the eye wearing the dual-focus lens relative to that wearing the single vision distance lens,” the investigators found. Similar results were seen in the second period when the lenses were swapped.
Furthermore, visual acuity and contrast sensitivity were no different with the dual-focus lenses and the single focus lenses, and eyes wearing the dual-focus lens were able to accommodate to near targets via the central zone, the team reports.
They conclude 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.”
Effect of Dual-Focus Soft Contact Lens Wear on Axial Myopia Progression in Children