A new study suggests that having a child with rapidly worsening nearsightedness wear bifocals may help them maintain better vision.
Nearsightedness, or myopia, causes people to have trouble seeing objects clearly at a distance, and for some, the condition progresses quickly. The tendency toward rapid progression is believed to be inherited, and it has been unclear whether anything can be done to slow it.
One potential tactic is to prescribe children bifocals — lenses that are split into two sections, with the upper half for distance vision and the lower half for near vision. But studies so far have yielded mixed results.
For the new study, reported in the Archives of Ophthalmology, researchers recruited 135 Chinese-Canadian children with rapidly progressing nearsightedness.
The researchers randomly assigned the children to either keep wearing single-focus lenses or get a new prescription for bifocals; half of the latter group were given prism bifocals, which help the eyes work together.
Over the next two years, children wearing either type of bifocal showed a moderately slower rate of nearsightedness progression, the researchers found.
As for why bifocals might help these children, lead researcher Dr. Desmond Cheng explained that, for most people, objects viewed at a close distance do not focus completely on the retina, but slightly behind it — in what is called hyperopic defocus.
If that situation is maintained for long periods, as may be the case when a person does a lot of reading or other “near work”, it may actually contribute to nearsightedness progression, according to Cheng. Bifocals, he said, interrupt this hyperopic defocus, and may thereby help slow myopia progression.
