Purpose: To evaluate the impact of age on myopia progression with dual-focus and single vision daily disposable contact lenses.
Methods: Myopic children aged 8 to 12 years, with no prior contact lens experience, were enrolled in a 3-year, prospective, randomized, controlled, double-masked, multicenter study (Part 1). Subjects wore either a dual-focus daily disposable soft contact lens (DFCL, n=65) or a single vision control contact lens (SVCL, n=70), both omafilcon A (CooperVision Inc.). Subjects’ baseline myopia ranged from -0.75 to -4.00D and astigmatism was ≤0.75 D. After 3 years, the control group were refitted with the DFCL (n=56) while the test group continued with DFCL (n=52) for Part 2 of the study. Cycloplegic spherical equivalent autorefraction (SE) and axial length (AL) were measured at baseline and every 12 months through 5 years. In order to assess myopia progression as a function of age, annual changes in SE and AL were analysed by pooling across treatment years, isolating the subject age at the beginning of each 1-year period.
Results: The average (±SD) annual myopia progression rates for the SVCL group decreased from -0.70±0.51D at age 8 to -0.25±0.32D at age 14. Myopic progression in the DFCL group was slower at all ages (all p<0.05) except age 14 and decreased from -0.38±0.27D to -0.13±0.28D from 8 to 16 years of age. The annual elongation rate of axial length in the SVCL control eyes decreased from 0.30±0.13mm at age of 8 to 0.13±0.09mm at 14 years of age. In contrast, the DFCL elongation rate slowed from 0.16±0.06mm at age 8 to 0.05±0.08mm at age 16. Annual progression rates in both groups reduced significantly as a function of age for both SE and AL (p<0.0001).
Results: Annual myopia progression rates were significantly slowed by wearing of the DFCL initiated between ages 8 and 14, and, as age increases, progression rates continue to slow. Therefore, observed treatment effects in myopia control clinical trials may be dependent on the age of the subjects and study duration. These findings suggest that there is an enhanced benefit from commencing myopia control treatment as early as is feasible.