CHICAGO — For slowing the progression of myopia in children, a dual-focus contact lens (DFCL) proved significantly better than a single-vision lens, and efficacy was maintained out to 3 years, researchers reported here at Academy 2017, the Academy of Optometry's Annual Conference.
"The [DFCL] definitely slowed the progression of myopia as measured by refractive error change and axial length growth, the two major outcomes," said Paul Chamberlain, BSc, manager of clinical research at CooperVision, Inc. "The contact lens reduced myopia progression on average, across the population, by about half, and this was sustained over 3 years of study."
Although multifocal contact lenses have been used off-label, with some success, in children with myopia, the CooperVision product, MiSight, is designed somewhat differently and could be more effective, he said. It has two powers that are located on the lens in a concentric ring design. The two rings of myopic defocus are presumed to be responsible for enhanced efficacy.
"We are putting the best image in front of the retina, and this helps slow the growth of myopia," Chamberlain told Medscape Medical News.
The lens is available in Europe and Asia, but is not yet approved by the US Food and Drug Administration.Multicenter Randomized Trial
To test the lens, the researchers enrolled 144 children, aged 8 to 12 years, in a prospective, randomized, double-bind, multicenter trial. For 3 years, participants wore the DFCL or a single-vision soft contact lens (SVCL), specifically the ProClear 1 Day contact lens, also manufactured by CooperVision. "We chose ProClear 1 Day because it is also a daily disposable contact lens and is exactly the same, apart from the optics. This means we can do a good job of masking the study arm, and the differences we are see are only those due to the optics," Chamberlain said.
Spherical equivalent cycloplegic refractive error (SERE) and axial length, the key endpoints for assessing myopia progression, were measured at baseline and every 12 months for 3 years. A linear mixed model, including fixed factors such as lens type, site, and sex, was used to compare the adjusted change in SERE and axial length. The model also included covariates such as age, baseline refraction, and wearing times.
At baseline, the participants' myopia ranged from 0.75 to 4.00 D, and astigmatism measured less than 1.00 D.
Overall, 108 subjects completed the 3-year study: 56 in the SVCL group and 52 in the DFCL group. Chamberlain considered this a good rate of compliance. "We found acceptance to be remarkably high. This is multifocal optics, and they are not always completely accepted by presbyopes, let alone young children," he said. "We showed it was universally accepted."Long-term Results
Compared with the SVCL, the DFCL significantly reduced the progression of myopia at 12, 24, and 36 months. Table 1 shows the mean difference between the groups in SERE and axial length.
Table 1. Mean Difference in Indicators of Myopia Progression for Dual-Focus vs Single-Vision Contact LensEndpoint12 Months (% Change)24 Months (% Change)36 Months (% Change)Adjusted Effect/P ValueSERE0.40D (69%)0.54 D (59%)0.73 D (59%)0.69 D/<.001Axial length0.15 mm (63%)0.24 mm (53%)0.32 mm (52%)0.29 mm/<.001
In all comparisons, the DFCL improved measurements by more than 50%, and the treatment effect was independent of age, sex, ethnicity, or baseline refractive error. Significantly higher rates of myopia progression were found for the control group at each visit (P < .001).
A change of more than 0.75 D at 36 months was observed in 73% of the control group vs 33% of the DFCL group. Researchers determined that DFCL wearers were 11.5 times more likely to have no change in their prescription, Chamberlain added.
The study also examined the correlation between change in SERE and change in axial length at 12-, 24-, and 36-month visits, and found the correlation to be "remarkably high" (R2 = 0.81; P < .001). "You want these two measures to correlate well, and the study shows just that," he said.
Age, research site, and sex were significant factors in change in SERE and axial length (P < .05), but interaction of these factors with lens type was not significant. Baseline myopia or wearing time were also not significant factors in myopia progression."Accumulation of Effect"
Donald Mutti, OD, PhD, the EFF Wildermuth Professor in the Ohio State University College of Optometry in Columbus, commented that the study importantly provides long-term data. Dr Mutti is an investigator in the National Eye Institute-sponsored randomized controlled Bifocal Lenses in Nearsighted Kids (BLINK) trial of multifocal contact lens for myopia control.
"What's important in this study is that there is 3 years' worth of data, vs 1 or 2 years of data [in other studies], showing that the effect of the [DFCL] is accumulating over time," Dr Mutti told Medscape Medical News. "A lot of studies show a good effect, say, in the first or second year, but 3-year studies are rare."
He continued, "To have an accumulating benefit over that length of time is new, it's really important, and it's a clinically meaningful 59% effect. Most studies of multifocal soft lens or overnight orthokeratology have had an effect size of about 30%."
Dr Chamberlain is an employee of CooperVision, Inc, which sponsored this study. Dr Mutti has disclosed no relevant financial relationships.
American Academy of Optometry (AAOpt) 2017. Presented October 12, 2017.
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