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Retinal Devices and Artificial Cells to Restore Vision
There has been a lot of research on artificial retina and stem cell treatments to restore normal human level vision.

Thanks to the complex sensory system we can hear, smell, see, feel and taste the world around us. Each sense is important and has unique anatomy that can help us modify our behavior and adapt to the environmental changes. When one of the senses is damaged, remaining senses intensify their function (blind people hear better than people with normal vision). Sight can be impaired in numerous ways. Due to complicated anatomy of eye and associated neuronal connections, development of a device that could help restore damaged vision is truly a challenge. Luckily, advanced technology allowed scientists to design couple of prototypes that will soon become available for a worldwide use.

Eye is the central organ for the sense of vision. Retina is photosensitive part of the eye; it consists of the rods and cones (modified neuronal cell) that are responding to the light by generating action potential that is traveling through the optic nerve (formed by the retinal ganglion axons) to the visual cortex where image will finally be created. Blindness is usually associated with retinal damage, either as a consequence of an accident or as a result of diseases like macular degeneration, retinitis pigmentosa, cone-rod dystrophy…..

Two types of retinal devices are currently under investigation.

Epiretinal device consists of internal and external part. Silicon platinum electrode array (internal part) is placed on the inner surface of the retina. External part of the device consists of glasses containing miniature camera. Images captured by camera are wirelessly sent back to antenna in the inner electrode array. Electric impulses from the array will trigger remaining retinal cells and generate electric signal (visual information) that will travel to the brain via optic nerve. Patients need to learn how to interpret visual patterns. Disadvantage: external part of the device can be bulky and patient needs to move head to “update” visual information. Also, internal part needs to fit perfectly to prevent disturbance of the nearby axons (it can be fixed to the retina using miniature tacks). Epiretinal device finished clinical trials successfully; soon it will become available in couple of European countries.

Subretinal device is placed on the surface of the retina, between retinal photosensitive cells and retinal pigment layer. This prototype stimulates retinal cells directly. It consists of silicon pad containing light sensitive micro-photodiodes. Electric signal, generated by light, passes to the retinal cells and further to the brain. This device doesn’t need external apparatus, but it requires power supply to amplify up-coming light signals, which is the main disadvantage of the subretinal device. Problem could be solved using the artificial cells able to generate electricity. Experiments of that kind were conducted couple years ago, when group of scientists wanted to design artificial cell using eel’s electrocyte as a cell model. Eel use electrocytes to stun the prey, but they are also important for detection of various stimulus. Biochemistry behind the cell electricity is relatively simple. Cell voltage and electric current are associated with ion channels activity. Exchange of sodium and potassium currents over the cell membrane alter the cell voltage and trigger electric current. Electrocytes act like a nervous cells - initial signal travels fast and it is easily transferred to the next cell. Different types of ion channels will be more or less densely distributed along the cell membrane (depending on their function). Electric eel can generate up to 600 volts of electricity thanks to thousand of simultaneously firing electrocytes. Scientists wanted to investigate what are the main ion channels and find a way to increase produced electricity by altering their functions. Using the software, numerical design optimization method was applied to investigate which channels produce electricity under which circumstances. After main channels were detected, scientists enhanced their activity and ended up with the cell that could produce 40% more electricity than electrocyte in the natural environment. This type of cells could serve as bio-battery. Using 4 mm wide layer of electrocytes, 300 microwatts of electricity was generated. That amount of electricity would be enough for various implanted micro-devices, including retinal device. Artificial cell is still under investigation.

Although described devices are still not available (at least not everywhere), nor they are perfect, blind people are closer than ever to regain their sight.

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Being able to restore sight to people with impaired vision could greatly improve quality of life for many people. Many things in our world are designed for use by people with normal vision. To improve vision in patients could be life-changing.

In February 2013, the United States Food and Drug Administration approved the first artificial retina for use in human patients. The artificial retina helps take over the function of light-sensing cells in the retina, and sends that information to the brain. The device, called the Argus II, uses special glasses that contain a video camera and recording device. The glasses send the recorded information to patient’s eye to process. The Argus II was approved for patients suffering from retinitis pigmentosa, a genetic disorder in which light-sensing photoreceptor cells are degraded over time.

The Argus II received humanitarian approval, which limits the number of people eligible to use the device until it has been proven safe and effective. The Humanitarian approval is reserved for devices to treat diseases affecting fewer than 4000 people. This special approval makes it easier for companies to target rare disorders, and get treatments to patients more quickly. While the Argus II does not fully restore vision, it helps patients to complete tasks in daily life more easily by improving their ability to sense light.

Artificial retina devices like the Argus II have the potential to help many people. The receptors in the eye are crucial for good vision. When cells containing these receptors are unable to function, the eye cannot process information and send it to the brain. Finding a way to artificially replace damaged cells and receptors may be the only way to restore vision.
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