Human retinas grown in a dish explain how color vision develops

Biologists at Johns Hopkins University grew human retinas from scratch to determine how cells that allow people to see in color are made.

The work, set for publication in the journal Science, lays the foundation to develop therapies for eye diseases such as color blindness and macular degeneration. It also establishes lab-created "organoids" as a model to study human development on a cellular level.

"Everything we examine looks like a normal developing eye, just growing in a dish," said Robert Johnston, a developmental biologist at Johns Hopkins. "You have a model system that you can manipulate without studying humans directly."

Johnston's lab explores how a cell's fate is determined – or what happens in the womb to turn a developing cell into a specific type of cell, an aspect of human biology that is largely unknown.

Here, he and his team focused on the cells that allow people to see blue, red and green – the three cone photoreceptors in the human eye. While most vision research is done on mice and fish, neither of those species has the dynamic daytime and color vision of humans. So Johnston's team created the human eyes they needed – with stem cells.

"Trichromatic color vision delineates us from most other mammals," said lead author Kiara Eldred, a Johns Hopkins graduate student. "Our research is really trying to figure out what pathways these cells take to give us that special color vision."