Color sorting in the retina by natural optical fibers

An interdisciplinary research group from the Technion revealed for the first time the optical role of glial cells in the retina for the improvement of vision. Until today, the retina was known for its conversion of light into electric signals as well as the initial processing of the visual information. However, the Technion group showed that the retina is also a sophisticated optical structure.


The retina of the eye: Light, arriving from above, is guided towards the photoreceptors (blue layer at the bottom) by glial cells acting as optical fibers. The glial cells sort the light by its colors, where the green and red (shown) pass into the corresponding cones, while the blue-violet is scattered to nearby rods.

The research shows how light passes the eye to fall on the retina, only to be separated into colors by funnel-shaped glial (Müller) cells, functioning as optical fibers spanning the retinal depth.

These cells collect and guide efficiently the green-red colors down to the cone photoreceptors, the light detectors responsible for day time color vision, and, at the same time, allowing the blue and violet colors to scatter out to the surrounding rod photoreceptors, active at night time. This color separation improves the daytime peripheral vision up to ten times, without impairing night vision.

The light guiding and color sorting explain why the vertebrate retina has a seemingly inverted structure, with photoreceptors set behind layers of neural cells and cell nuclei, rather than in front of them.

The researchers built a computer model predicting the color guiding in the retinas of humans and other diurnal mammals. This model was validated in the laboratory, where light was measured while passing through the retina, along the glial cells, down to the photoreceptors. Indeed, the experiments showed the concentration of green-red light inside the glial cells, down to the cones, with the blue-violet colors to the nearby rods.

The research was performed by graduate students Amichai Labin and Shadi Safuri, supervised by Erez Ribak and Ido Perlman, from the Faculties of Physics and Medicine, and was published in Nature Communications.