Colour filtering in the retina for improved sensitivity
In order to see single photoreceptor cells in the retina, we used hardware and software tools, getting close to the resolution limit, a tenfold improvement. Transparent layers which come in front of the photoreceptors are barely seen by direct imaging, but they play a major role in improving acuity. Radial cells of higher refractive index channel some colours directly into the corresponding photoreceptors to improve their responsivity. Other colours are scattered around, and serve for night vision. Finally, simulations and experiments explained the reason why the retina is inverted, with the photoreceptors behind the neural layers.