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Wearing progressive-addition lenses (PALs)â€”otherwise known as no-line bifocalsâ€”seems to slow the progression of nearsightedness in elementary school-aged children, but do they do so well enough to make progressive lenses the clinical standard for children with myopia?
Wearing progressive-addition lenses (PALs)-otherwise known as no-line bifocals-seems to slow the progression of nearsightedness in elementary school-aged children, but probably not enough to make fitting all nearsighted children with PALs the clinical standard.
In a small study known as the STAMP trial (Study of Theories About Myopia Progression), an optometrist from the University of Houston and colleagues from the Ohio State University randomized 85 nearsighted children aged between 6 and 11 years to wear either single-vision lenses (SVLs), which are usually prescribed for myopic children, or PALs for 1 year. All the children then wore SVLs for a second year. All the children had high accommodative lag.
In addition to observing and objectively testing the children, the investigators surveyed the caregivers of the children regarding both the children’s outdoor activities and near-sight indoor activities such as reading and computer use.
The researchers found that the myopia in the children who wore the no-line bifocals progressed slower than that in the children who wore the SVLs the first year. And the effect, although small, persisted to the end of the second year, when all the children were wearing SVLs. The researchers found no association between accommodative lag and progression of myopia.
The mechanism by which the PALs slow progression of myopia involves the design of the lenses, which alters the blur in the eye's peripheral vision. The investigators say the results do not warrant fitting all nearsighted children with no-line bifocals solely for the purpose of slowing myopia, and it remains unclear whether the treatment effect remains indefinitely, but the findings offer hope that the development of other optical lenses could further halt progression of the condition.
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