Words Ria Rivera
Having an implant stuck somewhere in your eye might not be the most comforting thought, especially if this implant squirts chemicals. But to people who suffer from retinal diseases such as age-related macular degeneration and retinitis pigmentosa, it may very well be the only solution that may shed light to their dim situation.
Unveiled last year by engineer Laxman Saggere of the University of Illinois at Chicago, the implant is a solar-powered chip that stimulates retinal cells by spraying them with neurotransmitters. It flexes in response to very low intensity light that strikes the retina. Multiple actuators on a single chip pick up the details of the image focused on the retina, allowing some "pixels" to be passed on to the brain and therefore letting the person see.
The retina, which lines the back and sides of the eyeball, contains photoreceptor cells that release signaling chemicals or neurotransmitters in response to light. The neurotransmitters then pass into nerve cells on top of the photoreceptors, which relay the signals to the brain where they're translated into images.
What makes Saggere's work promising is the fact that unlike other implants that apply an electrical charge directly to the retinal cells, his solar-powered implant does not cause the cells to heat up. And because it relies merely on the light of the sun, it uses very little power and does not need external batteries.
The current prototype consists of a flexible silicon disc measuring about 1.5 millimeters in diameter and 1.5 micrometers in thickness. When light hits a silicon solar cell next to the disc, it produces a voltage. This triggers the lead zirconate titanate (PZT), the layer of piezoelectric material on which the solar cells are connected, to change in shape and push down the silicon disc. In the future, a reservoir will sit underneath the disc and this action will squeeze the neurotransmitters out onto the retinal cells.
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