Insufficient light during pregnancy can lead to unchecked blood vessel growth in the retina, seen here in a mouse’s eye.
Mothers need light exposure during pregnancy for healthy eye development in babies, according to a study in the January 16 online edition of Nature.

Using a mouse model, investigators found that activation of a light-response pathway must happen during pregnancy to initiate the carefully choreographed program that produces a healthy eye. Specifically, they say it is important for a sufficient number of photons to enter the mother’s body by late gestation.

Before this, scientists had assumed that if light played a role in the development of the eye, it would happen only after birth.

“This fundamentally changes our understanding of how the retina develops,” says study co-author Richard Lang, PhD, a researcher in the Division of Pediatric Ophthalmology at Cincinnati Children’s Hospital Medical Center. “We have identified a light-response pathway that controls the number of retinal neurons. This has downstream effects on developing vasculature in the eye and is important because several major eye diseases are vascular diseases.”

One of those eye disorders in particular is retinopathy of prematurity.

The study involved several experiments in groups of laboratory mice raised either in the dark or in a normal day-night cycle.

Mice reared from late gestation under dark conditions exhibited expansion of hyaloid vessels and abnormal retinal vascular growth. The unchecked vascular growth was driven by vascular endothelial growth factor (VEGF-A).

In normal circumstances, the light-response pathway modulates VEGF-A to help prevent uninhibited vascular growth. These vessels naturally regress in mice before the eyelids open 10 days after birth, but they persist if the mouse fetus receives insufficient light in the womb—which shows that the eye needs light to develop during pregnancy.

The research team will now study how the light-response pathway might influence the susceptibility of pre-term infants to retinopathy of prematurity and other diseases of the eye, Dr. Lang says.

Rao S, Chun C, Fan J, et al. A direct and melanopsin-dependent fetal light response regulates mouse eye development. Nature. 2013 Jan 16. [Epub ahead of print]