For children with Down syndrome, vision issues such as strabismus, accommodative lag, refractive errors and reduced visual acuity come with the territory. Studies show strabismus alone can be found in 15% to 47% of all children with Down syndrome. But over the last few years, researchers have been considering bifocals as a method to combat the elusive alignment disorder. Now, a publication in Acta Ophthalmologica is showing that bifocals with full correction of refractive error reduce the manifest angle of strabismus within a few weeks.

The study looked at 119 children between the ages of two and 16 who have Down syndrome. The subjects were randomly prescribed bifocal or unifocal glasses (with full correction of refractive error in cycloplegia). The 15 participating centers, all in the Netherlands, followed the participants across four visits over the course of a year, noting changes in their strabismus as well as refractive errors, accommodative accuracy, binocularity and stereopsis.

The bifocals didn’t work across the board, and they didn’t affect refractive and accommodative errors in either intervention group. But the modality did have one notable impact. The manifest angle of strabismus was significantly reduced in the subjects given bifocals. This improvement was first observed approximately six weeks in, shortly after the subjects received their new correction—and the improvement persisted throughout the course of the year. The researchers note that they did exclude the results of two subjects with the largest manifest angles of strabismus (45 prism diopters), one in the bifocal group and one in the unifocal group, because they so strongly weighted the results. But, they add, even if they had left those two in, the treatment difference for the bifocal group as a whole would still have been significant.

Bifocals with full correction of refractive error help relieve the manifest angle of strabismus in children with Down syndrome. The angle of strabismus can be reduced and, in some cases, orthotropia can be achieved. “Bifocals could be an important solution for children with Down syndrome and strabismus,” the researchers wrote, adding that the treatment “is preferable to surgical interventions in view of the large number of contraindications for anaesthesia.”