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Graphene is being touted as a ‘wonder material’ with all kinds of potentially ground-breaking applications and one of those potential applications is the treatment of blindness.
Blindness has a number of causes, including genetic disorders, glaucoma, and age-related macular degeneration. Researchers looking to develop a graphene-based cure for blindness have taken a number of different approaches. One effort involves the use of a camera connected to an artificial retina made of graphene. Another approach involves a graphene retina designed to be a replacement for a damaged retina.
A Graphene Interface
A team of researchers at The University of Pittsburgh is looking to treat blindness using a system of cameras and processors that gather light and translate it into electrical impulses for the brain to turn into images.
The retina, situated at the back of the eyeball, has specialized photoreceptor cells known as rods and cones that transform incoming light into nerve signals. These electrical impulses are passed into the brain via the optic nerve where they are transformed into imagery. Numerous diseases can harm or destroy retinal tissue, which can result in vision loss or total blindness.
In 2013, the Food and Drug Administration gave limited approval for a camera-based system to treat visual impairment brought on by the rare genetic condition retinitis pigmentosa. The FDA authorized the system, known as the Argus II Retinal Prosthesis System, under a humanitarian designation for individuals with rare medical conditions. The system uses a camera and a video processing unit to convert the light into electronic signals that are wirelessly sent to an artificial retina at the back of the eye, which passes information along to the brain. The device can help patients perceive pictures and movement.
In 2018, the FDA authorized a more advanced system, called the IRIS II, that was created by the same scientists. It has an implant with more electrodes to produce a clearer picture, a solar panel to power itself and a safer implantation process. The IRIS II was designed with graphene to create a superior interface with neural tissue in the retina compared to the Argus II system.
The IRIS II is expected to be used on individuals with retinitis pigmentosa and with age-related macular degeneration. Animal-based trials have indicated the IRIS II can enhance vision above the World Health Organization threshold for blindness.
A Graphene Retina
In a separate effort, scientists at the University of Texas at Austin and Seoul National University have successfully tested an ultrathin artificial retina made from graphene and molybdenum disulfide that could be superior to existing implantable visualization technology to treat blindness, possibly giving sight to millions of individuals with retinal diseases.
Medical scientists have had some success with silicon-based retinal implants, which have partially restored vision in some patients. However, these devices are stiff, flat and fragile, making it challenging for them to reproduce the normal curvature of the retina. Consequently, silicon-based retinal implants often create fuzzy or distorted images and can cause long-term damage to adjacent eye tissue, including the optic nerve.
The Korean-American study team looked to create a slimmer, more flexible option that would better imitate the form and function of a normal retina. To do this, scientists used graphene, molybdenum disulfide, thin layers of gold, alumina and silicon nitrate to produce a flexible, high-density and rounded sensor array. The device, which looks like the exterior of a compressed soccer ball, conforms to the dimensions of a normal retina without mechanically upsetting it.
In laboratory and animal trials, the device readily absorbed light and sent it to an external circuit board. The circuit board held all of the electronics required to process light, stimulate the retina and gather signals from the visual cortex. By using these trials, the scientists were able to establish that their prototype is biocompatible and able to imitate the structural attributes of the human eye.
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