Vitamin A & Thyroid Hormones Key to Sharp Human Vision Development

Study reveals new insights into how the human eye develops high-acuity vision during fetal development.

Published on Feb. 14, 2026

Got story updates? Submit your updates here. ›

Researchers at Johns Hopkins University have discovered that the development of sharp human vision during early fetal development is driven by an interplay between a derivative of vitamin A and thyroid hormones within the retina. This challenges the long-held belief that the precise arrangement of light-sensing cells in the retina is achieved through cell migration, and instead shows that the cells actually undergo a conversion process to achieve the optimal cone distribution necessary for high-acuity vision.

Why it matters

This finding offers new avenues for treating age-related vision disorders like macular degeneration and glaucoma, as it provides a potential blueprint for developing cell-based therapies to restore lost vision. The insights gained from studying lab-grown retinal organoids could lead to innovative strategies for treating debilitating eye diseases that currently have limited treatment options.

The details

The research team, led by Robert J. Johnston Jr. of Johns Hopkins University, used lab-grown retinal organoids to observe the cellular processes that shape the foveola, the central region of the retina responsible for high-acuity vision. They found that the development of the specific cone cell distribution in the foveola occurs in two phases. Initially, blue cones are present in the foveola, but by week 14 of fetal development, these blue cones begin to convert into red and green cones. This conversion is driven by the breakdown of retinoic acid, a vitamin A derivative, which limits the production of new blue cones, and the active encouragement of thyroid hormones, which cause the existing blue cones to transition into red and green cones.

  • Between weeks 10 and 12 of fetal development, a limited number of blue cones are present in the foveola.
  • By week 14 of fetal development, the blue cones in the foveola begin to transform into red and green cones.

The players

Robert J. Johnston Jr.

An associate professor of biology at Johns Hopkins University and the lead researcher on this study.

Katarzyna Hussey

A former doctoral student in Johnston's lab and now a molecular and cell biologist at CiRC Biosciences in Chicago.

Got photos? Submit your photos here. ›

What they’re saying

“First, retinoic acid helps set the pattern. Then, thyroid hormone plays a role in converting the leftover cells. That's very important because if you have those blue cones in there, you don't see as well.”

— Robert J. Johnston Jr., Associate Professor of Biology (Proceedings of the National Academy of Sciences)

“The goal with using this organoid tech is to eventually make an almost made-to-order population of photoreceptors. A big avenue of potential is cell replacement therapy to introduce healthy cells that can reintegrate into the eye and potentially restore that lost vision.”

— Katarzyna Hussey, Molecular and Cell Biologist (Proceedings of the National Academy of Sciences)

What’s next

The research team is now focused on refining their organoid models to more accurately replicate the complex functions of the human retina, with the goal of developing new cell-based therapies for vision loss.

The takeaway

This study represents a significant advancement in understanding the intricacies of human vision development, offering a promising new direction for the treatment of debilitating eye diseases like macular degeneration and glaucoma, which currently have limited treatment options.