Scientists Uncover Surprising Role of Vitamin A in Development of Sharp Human Vision

What if some of the cells responsible for sharp vision begin life as a completely different type of light-sensitive cell? Scientists have discovered that developing human eyes may transform blue-light-detecting cells into red- and green-sensitive cells, revealing an unexpected mechanism behind our ability to see fine details.

Published in the Proceedings of the National Academy of Sciences, the study conducted by researchers at Johns Hopkins University investigated how vitamin A signalling and thyroid hormones influence the development of specialised cells in the human retina.

Researchers focused on the foveola, a tiny region at the centre of the retina responsible for exceptionally sharp central vision, including reading, recognising faces and identifying fine details.

Unlike other retinal regions, the foveola contains red- and green-sensitive cone cells but lacks blue-sensitive cones.

To understand how this arrangement develops, scientists used laboratory-grown human retinal organoids that mimic important stages of fetal eye development.

The findings revealed that during weeks 10 to 12 of fetal development, a small number of blue-sensitive cones are initially present in the foveola.

However, by approximately week 14, these cells appear to transform into red- and green-sensitive cones.

Importantly, researchers identified two biological mechanisms involved in this process.

Retinoic acid, a molecule derived from vitamin A, helps establish the retinal pattern by limiting the development of blue-sensitive cones in the central region.

Thyroid hormones subsequently appear to promote the conversion of remaining blue-sensitive cells into red- and green-sensitive cones.

The discovery challenges a longstanding theory suggesting that blue cones simply migrate away from the developing foveola.

However, researchers acknowledged that cell migration cannot yet be completely ruled out.

The findings could eventually help scientists develop more accurate retinal organoids and explore cell replacement therapies for conditions such as macular degeneration.

Nevertheless, these applications remain experimental, and the results do not suggest that vitamin A supplementation can restore vision in adults.

REFERENCE: Katarzyna A. Hussey, et al.; A cell fate specification and transition mechanism for human foveolar cone subtype patterning. Proceedings of the National Academy of Sciences, 2026; 123 (7) DOI: 10.1073/pnas.2510799123