A surprising vitamin A discovery is changing what scientists know about vision
Scientists at Johns Hopkins University have uncovered a surprising process that helps humans develop sharp vision before birth, challenging decades of assumptions about how the eye forms. Using miniature human retinas grown in the lab, researchers discovered that a vitamin A derivative and thyroid hormones work together to shape the foveola, the tiny region at the center of the retina responsible for our sharpest…
Key points
- Johns Hopkins scientists found vitamin A derivative retinoic acid and thyroid hormones shape cone cells in the foveola.
- Blue cones initially in the foveola appear to transform into red and green cones by week 14 of fetal development.
- The findings challenge a 30-year-old model and may aid research into macular degeneration and other vision loss conditions.
Scientists at Johns Hopkins University have discovered a surprising role for a vitamin A derivative in human vision development. The research shows how this molecule works with thyroid hormones to form the foveola, the tiny retinal region responsible for the sharpest central vision, according to a study published in Proceedings of the National Academy of Sciences.
The findings challenge an explanation that has stood for roughly 30 years. The work could also advance research into treatments for macular degeneration, glaucoma and other conditions that cause vision loss.
How the retina was recreated
The team grew miniature versions of human retinal tissue, called organoids, from fetal cells. By observing these organoids over several months, the scientists could follow changes that would be extremely difficult to study during pregnancy.
They focused on the foveola, which contains red and green cones but lacks blue cones. Although the foveola occupies only a small fraction of the retina, it is involved in approximately 50% of human visual perception, according to the researchers.
First, retinoic acid helps set the pattern. Then, thyroid hormone plays a role in converting the leftover cells.
— Robert J. Johnston Jr.
What the study found
During weeks 10 through 12 of fetal development, a small number of blue cones are initially present in the foveola. By week 14, these cells appear to have transformed into red and green cones.
Retinoic acid, produced from vitamin A, limits the formation of blue cones in the central region. Thyroid hormones then appear to encourage the remaining blue cones to change into red and green cones. The study does not establish that taking vitamin A supplements can improve sharp vision in adults.
