The human retina is built backwards, with the neurons in front of the photoreceptors rather than behind them, a new study has confirmed.
From a practical standpoint, the wiring of the human eye – a product of our evolutionary baggage – does not make a lot of sense.
In vertebrates, photoreceptors are located behind the neurons in the back of the eye – resulting in light scattering by the nervous fibres and blurring of our vision.
Recently, researchers at the Technion – Israel Institute of Technology have confirmed the biological purpose for this seemingly counterintuitive setup.
“The retina is not just the simple detector and neural image processor, as believed until today,” said Erez Ribak, a professor at the Technion – Israel Institute of Technology.
“Its optical structure is optimised for our vision purposes,” Ribak said.
Previous experiments with mice had suggested that Muller glia cells, a type of metabolic cell that crosses the retina, play an essential role in guiding and focusing light scattered throughout the retina.
To test this, Ribak and his colleagues ran computer simulations and in-vitro experiments in a mouse model to determine whether colours would be concentrated in these metabolic cells.
They then used confocal microscopy to produce three-dimensional views of the retinal tissue, and found that the cells were indeed concentrating light into the photoreceptors.
“For the first time, we’ve explained why the retina is built backwards, with the neurons in front of the photoreceptors, rather than behind them,” Ribak said.