German researchers gained fundamental new insight into the development of the eye defect coloboma, said a study on Wednesday.

Coloboma is a hole in one of the structures of the eye which occurs when the prenatal eye is developing and the choroid fissure fails to close.

Researchers at Heidelberg University and the University of Freiburg found the growth factor that controlled the flow of tissue which is essential for eye development. Using 4D microscopy, researchers determined that directed tissue flow transforms the optic vesicle into the optic cup during eye development.

"We now know that an organ forms through flow, not incrementally in steps. If the flow is stopped, coloboma develops. And we found the source of the stem cells in the eye, which is of major importance in stem cell research," said professor Jochen Wittbrodt of the Heidelberg Centre for Organismal Studies.

The new findings are not only critical for understanding the cause of coloboma, which is also called "cat eye syndrome" due to the oblong shape of the retina or iris, but also means that the understanding of eye development in vertebrates, including humans, is fundamentally different than has been taught for more than 70 years, said the study.

The results of their research were published in the journal eLife.