How light traverses the inverted vertebrate retina

In our eyes, as in the eyes of all vertebrates, images of the environment are projected on­to an inverted retina, where photons must pass through most of the retinal layers before being captured by the light-sensitive cells. Light scattering in these retinal layers must decrease the signal-to-noise ratio of the im­ages and thus interfere with clear vision. Sur­prisingly however, our eyes display splendid visual abilities. This apparent contradiction could be resolved if intraretinal light scatter­ing were to be minimized by built-in opti­cal elements that facilitate light transmission through the tissue. Indeed, we were able to show that one function of radial glial (Mül­ler) cells is to act as effective optical fibers in the living retina, bypassing the light-scatter­ing structures in front of the light-sensitive cells. Each Müller cell serves as a ‘private’ light cable, providing one individual cone photo­receptor cell with its appropriate pixel of the environmental image, thus optimizing spe­cial resolution and visual acuity.