Evolution put a notorious quirk in the vertebrate eye, placing the light-sensing cells on the back of the retina instead of the front. But evolution also seems to have found a high-tech work-around for this apparent mistake. Scientists now say that specialized cells transmit light through the retina's layers of various cells by acting like optical fibers.
In vertebrate retinas, light has to cross up to one-fifth of a millimeter of connective and nerve cells before reaching light-sensing cells.
But a team in Germany has shown that some of the layers' cells, shaped like funnels and called Müller cells, have a higher refractive index than the others. The scientists reached this conclusion by shining a laser through Müller cells taken from guinea pigs.