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Study findings not sufficient to recommend PALs for myopic children
A recent study has found that although the progression of myopia over a 3-year period in children wearing progressive-addition lenses (PALs) is slightly less than that of children wearing single vision lenses (SVLs), that difference is not sufficient to warrant a change in the way eye care professionals treat myopic children.
The Correction of Myopia Evaluation Trial (COMET), funded by the National Eye Institute, was designed to evaluate the progression of myopia in children randomized to these two different types of lenses.
Population and data collection
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Included in the study were 469 African-American, Asian, Caucasian and Hispanic children at four clinical centers in the United States, according to Jane Gwiazda, PhD, chair of the COMET study. All children had moderate amounts of myopia in both eyes and were between 6 and 11 years old at the time of the study.
Eligible children were randomly assigned to wear either PALs (n=235) or SVLs (n=234). Retention of children in COMET was very good, with 462 of the 469 children completing the 3-year study.
The primary outcome reflected a difference of 0.20 D of myopia progression between the PAL and SVL groups after 3 years. Increases in the overall length of the children’s eyes paralleled the changes in the amount of myopia in both the PAL and SVL groups.
Another key observation from COMET was that the treatment effect occurred in the first year and was sustained at the same level over the next 2 years.
Implications of the study
Dr. Gwiazda discussed what the findings will mean for the future of myopia treatment.
“The primary finding was that even though there is a small, statistically significant difference between the children wearing SVLs and those wearing PALs, the overall treatment effect is not enough to recommend that eye care professionals routinely prescribe PALs to myopic children,” she told Primary Care Optometry News.
Dr. Gwiazda also questioned the long-term value of the treatment effect, which appears to level off after 1 year.
“Typically, in the United States, myopia in children progresses 0.5 D per year on average,” she said. “If it is slowed even by half and progresses 0.25 D, you’ve got a 0.25-D difference after 1 year, and if the progression is sustained over subsequent years, it is not a very large treatment effect.”
The study found one distinct advantage of PALs over SVLs: PALs may slow progression of myopia in children by decreasing retinal defocus. Retinal defocus resulting from poor accommodation when children with low amounts of recent-onset myopia are engaged in close work may be a stimulus for increased eye growth and myopia progression.
“That was part of what the COMET rationale was, because progressive-addition lenses provide clear vision not only at distance, but also at intermediate distances and at near for reading,” Dr. Gwiazda said. “So the idea in prescribing PALs would be in decreasing defocus across the range of viewing distance that a child typically has.”
Although these findings did not alter the final recommendations of the study, they did suggest that some children could potentially reap greater benefits from PALs.
“We did find that children who had lower amounts of recent-onset myopia and who also had poor accommodative responses at near showed a larger treatment effect, in that the size of the treatment effect in that group of children was 0.55 D,” Dr. Gwiazda said. “That suggests that there could be some children for whom PALs may be beneficial, but that would require further study.”
For Your Information:
- Jane Gwiazda, PhD, is chair of the COMET study. She can be reached at New England College of Optometry, 424 Beacon Street, Boston, MA 02115; (617) 236-6234; fax: (617) 369-0188; e-mail: gwiazdaj@ne-optometry.edu.