Abstract
Purpose: :
To evaluate the effect of two types of novel progressive addition lenses (PALs) compared with the effect of a single vision low base curve spherical lens (SVL) on the progression of juvenile-onset myopia.
Methods: :
The design of the study is a parallel randomised controlled clinical trial. The two types of PALs had additions of 1.00 D (Lens B) and 1.50 D (Lens C) and high distance zone aspherisation comparable to the addition power. Myopic children between the ages of 6 and 12 were recruited in China and Japan. The children had an eye examination every six months. Number of children recruited was 197 with 169 completing the 24 months examination. The primary measurement of the progression of myopia was the change in mean sphere equivalent value derived from cycloplegic auto-refraction. Peripheral refraction measurements of both eyes along the horizontal meridian were also taken at a series of field angles out to ±35° using an open field auto-refractor. Multi-linear mixed effects regression modeling was used to obtain the progression rates in each group of children adjusted for confounding independent variables.
Results: :
Statistical analysis of adjusted progression rates has shown a mean progression (± SE) in the control group wearing SVL of -1.38 ± 0.09 D over 2 years. A statistically significant (p=0.02) but clinically not meaningful (0.27 ± 0.11 D or 20%) retardation of SER by Lens C relative to controls has been found but nearly all of it occurred in the first 12 months with no significant efficacy in the second year. Lens B, on the other hand has shown negligible efficacy in retarding progression of myopia with the exception of a small subgroup of children with no parental myopia (N=15) where a more steady 27% reduction in myopia progression (0.37 ± 0.17 D) was observed up until the final 24 months visit, which was statistically significant (p=0.04) and had the potential of being clinically significant if sustained in the 3rd year.
Conclusions: :
The retarding effect of Lens C after 24 months was similar to that found in some other studies with minimally aspherised PAL lenses having the same 1.50 D addition power. These results are consistent with the earlier findings that a fixed positive rotationally symmetrical aspherisation of a spectacle lens has no effect on myopia progression.
Clinical Trial: :
http://www.anzctr.org.au ACTRN12608000566336
Keywords: myopia • refractive error development • spectacle lens