APR 17, 2014
This double-blind, randomized study found that myopic-defocus lenses significantly slowed myopia progression and axial elongation in children.
The lenses incorporate concentric rings with an addition of +2.5 D alternating with normal distance correction, allowing for clear vision with simultaneous myopic defocus.
The two-year study included 221 children aged 8 to 13 years with myopia between −1.00 and −5.00 D and astigmatism ≤ 1 D. They were randomly assigned to wear the DISC (Defocus Incorporated Soft Contact) lens or single vision contact lenses.
Sixty-five children in the DISC group and 63 in the single vision group completed the study. There was a relatively high dropout rate due to lack of motivation to wear contact lenses.
Myopia progressed 25 percent more slowly for children in the DISC group (0.30 D/year vs. 0.4 D/year; P =0.031). Likewise, there was 31 percent less axial elongation for children in the DISC versus single vision group (0.13 mm/year vs. 0.18 mm/year; P = 0.009). Treatment effect correlated positively with DISC lens wearing time (P = 0.005).
For those able to successfully wear contact lenses, adverse reactions were low. The authors note that this prophylactic intervention is less invasive than pharmacological treatments and has great potential to slow myopia progression in children. They suggest that enhanced patient education may improve patient motivation, compliance and possibly treatment effect.
However, the optimum amount of myopic defocus for stopping myopia progression still needs to be determined. Also, improved contact lens material could further prolong safe wearing time, which was 10 hours due to the oxygen transmissibility level of the lens material. Since the myopia treatment effect increased to 58 percent in children who wore the lenses seven hours a day or more, the authors suggest that seven to eight hours a day may be an optimal wearing time.