Severely Visually Impaired Get Vision Back

Severely Visually Impaired Get Vision Back

Researchers resort to all methods in the fight against severe visual defects. An imaging chip can replace the eye's own light-sensitive cells, stem cells grown into a new retina and in a few years a new eye from a donor will be able to give severely visually impaired completely normal vision.

Transplantation is the solution when the cornea is damaged, and the lens becomes unclear. In the future, perhaps the whole eye can be replaced.

Artificial superlens gives sharpness at all distances

With age, our vision deteriorates because the lens of the eye becomes less clear and elastic. But in a few years, we might be able to get a new, artificial lens – Bionic Lens – that gives us supervision all our lives. The lens bends to the muscles of the eye, but since it is significantly more elastic than our innate lens, the muscles don't have to work as hard to focus.

Bionic Lens not only gives a youthful view, but also makes us look sharply in both longer and shorter directions. An upgrade of the lens can even allow projecting a screen directly into the eye.

For the brain to receive visual impressions from the eye, the optic nerve of the donated eye must be connected to the optic nerve of the recipient. It is difficult, because the optic nerve is a bunch of just over a million nerves.

Gene therapy replaces a defective gene in the eye

Several eye diseases caused by lesions of the retina can be treated with gene therapy, which gives the eye cells a healthy version of a defective gene.

The gene is induced into the cells using a virus. The virus's own pathogenic genes are removed, and the curative eye gene is inserted.

Patients with retinitis pigmentosa disease, for example, receive the RPE65 gene, which reforms the petticorn light-sensitive cells.

Today, a whole eye can only be transplanted along with half the face. So far, the operation has only been carried out on animals.

The first thing Rhian Lewis sees are small glimmers of light reminiscent of a starry sky, but after a few weeks of training, the brain has learned to interpret the impressions.

Instead, they turn to brilliant contours of the surroundings.

The picture is black and white and grainy, but for the first time in just over five years Rhian Lewis can actually see plates and cutlery on a set table, and she can also distinguish the hands on a dial.

A congenital visual defect has gradually broken down the light-sensitive neurons of the Rhian Lewis retina. Still, the 49-year-old British woman belongs to a small group of severely visually impaired who have regained parts of her vision after receiving an electronic image chip implanted in the retina.

The chip, called Alpha AMS, came on the EU market in 2016 and has been tested in clinical trials in Germany and in the UK.

The small chip acts as an electronic retina, so once it has had surgery into the eye, the visually impaired person only needs to activate it to see again.

The implant consists of basically the same kind of electronic image sensor as in a digital camera.

The chip replaces the light-sensitive cells destroyed in the visually impaired person’s eyes. It sends information about the light to the brain via the optic nerve, so that an image is created in the visual cortex.

Many possibilities for severely visually impaired

The picture chip is only part of the palette of advanced treatment opportunities that doctors today and in the near future can offer severely visually impaired people.

About 85% of all cases of severe visual impairment can probably either be prevented or treated with known technology.

In addition to electronic implants, the researchers work with biological solutions.

For example, stem cells can rebuild the destroyed tissue of the eye, while viruses entering the eye can reprogram the cells so that they start working properly.

Moreover, if all else fails, doctors will likely one day in the future be able to replace the entire injured eye with a normally functioning eye from a deceased donor.

There are an estimated 314 million severely visually impaired people.

The causes are often disease, wrong nutrition, congenital genetic defects or accidents. Severe visual impairment, where the person concerned cannot distinguish between light and darkness, occurs in around 39 million people, which corresponds to 0.5% of the world’s population.

The group severely visually impaired also includes those who do not even wear glasses or contact lenses look more than a tenth as good as an average vision person.

And even if you otherwise have perfect vision, you count as visually impaired if one’s field of vision is very limited.

A person is also counted as visually impaired if the eyes have so impaired sensitivity to light that extremely strong light is required to see them, or if he cannot distinguish between contrasts and gray tones so that the field of vision loses its contours.

Cataract (cataracts) is responsible for about half of all cases of severe visual impairment, even though the disease can be cured by replacing the lens of the eye.

Other common eye diseases affect the retina, and doctors have so far been unable to treat them.

These include macular degeneration (AMD) and diabetic retinopathy, which accounts for over thirteen per cent of the world’s cases of severe visual impairment.

Hereditary diseases such as retinitis pigmentosa can also cause the petticorn’s light-sensitive cells to be destroyed. It is these patients who can regain some of the vision with the image chip Alpha AMS.

Image chip uses healthy cells

The implant is a further development of another electronic retina, Argus II, which came on the market in 2011.

The predecessor worked in such a way that a video camera mounted on a pair of glasses filmed the surroundings and sent the image information to the electronic retina and from there to the brain.

Alpha AMS can do without the camera because the chip uses only the eye’s own lens to activate the electronic retina.

The image chip also has significantly higher resolution, 1,600 pixels (the points that create the image), compared to only 60 pixels in Argus II.

As a result, the severely visually impaired person gets a much more detailed picture of the outside world. As the crowning of the work, the chip also utilizes the layers of neurons that still work.

The retina consists of three layers of different types of neurons. The innermost layer, which is at the far end of the light, contains the light-sensitive cells called drops and rods, and it is in this layer, the chip is implanted.

When the light hits the light-sensitive cells, they send signals to the middle layer. There they are processed by another type of neurons that compare signals from nearby light-sensitive cells with each other to find contrasts and thus draw contours.

A large part of the visual impression is formed in this layer. Only the most essential information, about 0.06 per cent, is passed on to the brain via cells in the anterior layer of the retina.

In many visually impaired people with damage to the retina, the cell layers that provide the processing of the light signals are still intact.

The Alpha AMS chip uses the working cells to process the signals from the light-sensitive pixels before being passed on to the optic nerve, just as the signals from the retina’s own pins and rods. This significantly improves image quality.

Stem cells repair the retina

The Alpha AMS chip is certainly advanced, but at the same time primitive compared to a real retina.

Scientists have tried to transplant part of a retina from a deceased donor into the eye of a person who has lost sight as a result of damage to the retina.

So far, however, has not worked.

The big problem has been that the retina consists of 125 million neurons that accumulate in one million nerve connections, which make up the very optic nerve.

The many nerve connections from the donor retina are linked to the recipient’s optic nerve, and this is an impossible task for the surgeons to perform.

Therefore, doctors are now trying to cure defective retinas in a completely different way.

Instead of operating part of a retina from a donor, they inject stem cells into the eye and allow them to build the destroyed retina from scratch.

Stem cells have an outstanding ability to be shared and developed into other specialized cell types that the body needs.

When the stem cells are in place into the eye, they develop into the petticorn’s light-sensitive rods and drop, which on their own establish connections with the nerve cells in the two other layers of the retina.

The method was first tested in 2012 in two patients who have been severely visually impaired as a result of macular degeneration when the retina’s sharpest point yellow spot breaks down.

Steven Schwartz of the University of California, Los Angeles, in the United States, cultivated so-called embryonic stem cells in the laboratory under specific conditions that caused them to develop into the petticorn’s light-sensitive cells.

They were then injected behind the retina of the two patients, who in the following weeks clearly got better vision.

Stem cells form new retina

If the problem occurs as a result of more than one single gene or a blow, the damage can be repaired with stem cells rebuilding the destroyed part of the retina.

Before treatment, one patient could only sense the movement of a hand in front of the eyes, but already a week after the stem cells were injected into the eye, she could see how many fingers were shown.

After a month, she was able to read letters in excellent writing. In just a few weeks, stem cell therapy had made the visually impaired person partially seen.

In 2017, the technology was further developed by a research group at the RIKEN Center for Developmental Biology in Kobe, Japan, so that stem cells can now be extracted from the visually impaired person’s own skin cells and used to grow a new part of the retina.

Gene therapy is another hopeful method of curing visual impairment. This method is useful when visual impairment is caused by a particular gene.

The defective gene is then replaced by a healthy gene, which is indented into the cells of the eye using a virus.

In 2017, ophthalmologist Stephen Russell of the University of Iowa, USA, published the results of a gene therapy trial of 20 people with a congenital failure of the RPE65 gene, which causes the retina’s light-sensitive cells to be destroyed.

The experiment improved participants’ views so much that the US FDA agency approved in December 2017 the new treatment method, so that it can now be offered to all visually impaired Americans with errors in the current gene.

The whole eyeball is transplanted

Although scientists have developed a whole palette of electronic and biological therapies for different types of visual impairment, many visually impaired people are still unable to regain vision.

This applies, for example, to victims of accidents where the eye is exposed to significant physical injuries and patients with glaucoma, where the optic nerve is destroyed.

For them, the only hope is to get a new eye from a deceased donor. 

Doctors already use transplants from donors to treat damage to the cornea, the outermost part of the eye.

This effective procedure is performed 100,000 times a year, which means that almost as many corneas are transplanted together.

However, the leap to transplanting an entire eye is enormous.

Surgeon Kia Washington of the University of Pittsburgh, USA, who has transplanted eyes on laboratory animals, says it is currently impossible to transplant only the eyeball.

Doctors need to get their optic nerve all the way in between the two hemispheres of the brain to the area where the optic nerves of the right and left eye are crossed.

The surgeon has carried out the complicated procedure of 22 rats, 15 of whom survived.

One of the rats lived with his new eye for a full two years. However, studies showed that there were no electrical nerve signals from the retina and further through the optic nerve.

Kia Washington, however, is hopeful. Her research is supported by the Us Department of Defense, which hopes that eye transplants will be able to save the sight of the soldiers who have suffered accidents or explosions.

The researcher himself believes that the first full eye transplant can be carried out within ten years.

By then, most visually impaired people are likely to be able to regain some of their vision through either electronic implants, gene therapy, stem cells or transplantation.

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