The development of a bionic eye that mimics the dilation and contraction of the pupil brings us one step closer to helping people with eye defects.
Scientists have developed a thin material that sends signals in an artificial eye that resemble those of nerves. This allows the pupil in the eye to dilate and contract in response to changes in light intensity. In the future, this may help treat certain visual disorders.
Focus
Light enters the eye through the pupil and strikes the retina at the back of the eyeball. The retina then converts the light stimuli into nerve impulses, which are sent via the optic nerve to the brain for processing.
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The so-called pupillary reflex compensates for fluctuations in light intensity by adjusting the pupil size. This allows people to see clearly, while protecting the retina from bright light. This process may be disrupted in people with injury to the optic nerve or oculomotor nerve, which controls eye muscle movement. This can lead to double vision, sensitivity to light or farsightedness: problems focusing on close objects.
Artificial pupillary reflex
Xu Wentao, professor of photoelectric engineering at Nankai University in China, has now teamed up with his colleagues to develop a material that mimics the pupillary reflex in an artificial eye. “If we ever want bionic eyes, this light reflex has to be mimicked,” says Xu.
The thin material that makes this pupillary reflex possible is made of the mineral perovskite. It is known to act as an artificial synapse. A synapse is a piece of space between two neurons over which nerve signals are passed so that cells can communicate†
Xu’s team added a thin 625 nanometer material and an alloy fiber to an artificial eye model. In a lab experiment, Xu saw that when exposed to light, the thin material sent a kind of nerve signals to the fiber, which then caused the pupil to dilate or contract. “It works in all lighting conditions,” says Xu.
Day and night
The next step is to develop an artificial eye that perceives color, Xu says. “Human eyes can recognize millions of colors and decode them with high precision,” he says. “In the future, we plan to integrate this color perception into our artificial eye.”
neuroscientist Robert Lucas from the British University of Manchester thinks an artificial eye with pupillary reflex could be helpful. ‘Each artificial eye must be able to distinguish patterns in which the light intensity differs only a few percent. And that against a billion-fold variation in total light intensity in an environment in day or night light’, explains Lucas. ‘A light-sensitive pupil can be a way to tackle that problem.’ Such a pupil ensures that the total amount of light that reaches the detection surface remains more stable.