Background: We previously reported results of a randomized clinical trial of bifocals as a type of myopia correction for children with near-point esophoria. After 30 months, the rate of myopia progression in 36 children wearing bifocals averaged 0.40 D/yr compared to 0.50 D/yr in 39 children wearing single-vision glasses (p= 0.046, age-adjusted). Here we report on the 46 children in that study who completed 54 months of followup.
Methods: For each treatment group, we examined the pattern of change in myopia over the first and second halves of the 54-month period to see if the beneficial effect of wearing bifocals was present initially for those 46 children, as it was in the entire group, and to see if the myopia-slowing effect continued to accumulate during the second part of the study. During the last 12 months of the 54-month period, subjects were free to select any mode of myopic treatment, but this intent-to-treat analysis classified all children according to their original treatment assignment.
Results: During the first 24 months, the pattern of change in myopia differed between the two groups (p = 0.041), with those in bifocals showing slower progression. A similar trend was observed for vitreous chamber growth (p= 0.059). During the last 30 months, myopia progressed at a similar rate for both groups, including during the last year, when many subjects changed their mode of myopia correction.
Conclusion: Wearing bifocals instead of single-vision glasses caused a slowing of myopia progression evident during the first two years. During the subsequent two-and-a-half years of followup, the difference in the degree of myopia was maintained, but did not increase.