The Real Virtual Light
'Virtual Light' was coined by scientist Stephen Beck to describe a form of instrumentation that produces optical sensations directly in the eye without the use of photons.
It was popularised as the title of William Gibson's 1994 novel, in which the concept of virtual light was explored more deeply from an actual usage perspective.
However, at the time, the conceprt remained just that; a concept. We did not understand nearly enough about the workings of the optic nerve and preprocessing signals to the brain, to even begin to duplicate and replace functions of the eye. We know more now, but seemingly the more we discover, the less we find we actually know. That said, the first rather primitive virtual light devices, and those which would augment data gathering for virtual light, are just beginning to take form in laboratories across the world.
Boston Retinal Implant Project
The Boston Retinal Implant Project, partially based at the V.A. Medical Center in Jamaica Plain, is one of 22 programs around the world working to restore vision to the degenerative blind. Their work: a bio-electronic implant that delivers images to the brain via a connector the width of a human hair.
n its simplest terms, the device, which is implanted behind the retina at the back of the eyeball, works as a light transmitter. Only patients who were once able to see and have partially intact optic nerve cells are eligible for the procedure. This is because the implant grafts directly onto the optic nerve, and requires the pathways that would be laid down by the brain, to process signals from a working eye, in order to function. For this reason, it is impossible to fit the device to people who are blind from birth and have it functional, because the signal pathways are not present. That is not to say it would never be possible, onlty that we would have to regrow optical pathways to be successful, and that is far beyond current medical science.
Likewise, those who suffer from glaucoma are not eligable, due to damage that the implant would suffer from the pressure.
There has been this explosion of interest in this field because basically the technology in the last 20 years has become miniaturized enough and sophisticated enough so that for the first time we can imagine building something small enough to put in the eye, said Dr. Joseph Rizzo III, who founded the project in the late 1980s and co-directs the 36-member team.
Assembling this thing is really hard, said Wyatt, whose team of MIT researchers and engineers is responsible for designing and testing the implant. It has got to be waterproof, vapor-proof and very tiny. It has got to last for 10 years or more in the eye.
"We have one that sits and works now in a dish of saltwater. The one to last indefinitely should be ready sometime this summer. We expect to plant it in an animal this summer.
Saline is an ideal test for the device, because the fluid inside the eye is also very salty, and salt has a corrosive effect on non-biological materials, so the implant has to be both delicate enough to hug the sensitive cells of the back of the eyeball, and strong enough to withstand corrosion. Titanium has been chosen for its casing, to minimise corrosion on the delicate electronics inside.
Rizzo said the implant will not restore perfect vision, but will provide patients with a sense of their surroundings - to detect shapes and obstacles in their pathways. Ideally, Rizzo and his team say, patients will someday be able to recognize objects, faces and general detail.
?The thing is to significantly improve the quality of life for blind patients,? said Rizzo. ?What level of achievement that would actually be is hard to know. The idea of not having to use the white cane - to walk around, find the sidewalk, not run into a telephone pole, not walk into a car. Being able to navigate safely in an unfamiliar environment, that?s the big topic.?
One of the neat things about our implant is the whole device sits on the outside of the eye, except for a tiny strip of plastic, he said. So it doesnt invade the eyeball.
University of Illinois - Curved Optical Sensor
Traditional cameras and optical sensors have many shortcomings when compared to the organic eyeball. Artificial variants cannot cope simultaneously with a range of luminescent views, they cannot focus on differing focal lengths in the same image, and they cannot give a panoramic view like a natural eye, without distortion.
All three are decided nightmares when you are trying to use a camera lens to capture visual data about the outside world, and process it without the photons actually going through the eye. Thankfully, as of mid 2008, it looks like researchers at the University of Illinois, may have conquered the panoramic view without distortion problem.
Led by John Rogers of the University of Illinois at Urbana-Champaign and Yonggang Huang of Northwestern University in Evanston, Ill., the researchers announced their findings Aug. 7, 2008, in the journal Nature.
A new breed of curved optical sensors mimics the shape of the eyeball, and in doing so, eliminates the distortion curve with panoramic images. Its not quite at the stage of human implantation use yet; initial uses are for cameras and external sensor systems. However, since the process involves encasing the eye in a glass ball, it will beyond doubt prove a suitable design for replacing existing camera sensors in eye replacement as well.
The curve has been accomplished utilising an array of photodiodes bound flexibly with wire, that is then engraved on curved silicon created with a new method. The problem with making silicon curve, is that silicon does not naturally bend easily and cannot be forced into a hemispherical form without creases appearing in the material.
John Rogers at the University of Illinois at Urbana-Champaign and colleagues have now worked out a way around those problems, using conventional chip manufacturing technology.
They built their hemispherical electronic eye by first using conventional photolithography to build silicon photodiodes 500 micrometers square and 1 micrometer thick. These were then wired into a flexible 16-by-16 array using chromium and gold.
Separately, they created a 1-cm-wide hemisphere out of a stretchy plastic, and stretched it into a flat surface. That stretched surface, or "drumhead", was then pressed against the photodiode array.
The reformed array was then glued to a curved glass surface, and a conventional lens attached. It now resembled a human eye in construction, with light entering the lens from the front, and passing to the curved "retina" containing the matrix of photodiodes behind.
"This research is truly transformative," said Ken Chong, advisor in the National Science Foundation (NSF) Engineering Directorate, who is one of the officers overseeing the researchers' NSF grant. "Using simple mechanics principles, the researchers have produced, for the first time, electronic devices on a hemispherical surface so that they can take images much like those captured by the human eye."
"Mechanics helps to reduce the stresses and strain in components, and guide and optimize the system design," said Yonggang Huang, Joseph Cummings Professor of Civil and Environmental Engineering and Mechanical Engineering, Northwestern University, who worked with his team to model the mechanical properties of the design so that it could be manufactured.
"We believe that some of the most compelling areas of future application involve the intimate, conformal integration of electronics with the human body, in ways that are inconceivable using established technologies," said Rogers, who is also affiliated with the Beckman Institute for Advanced Science and Technology and the Frederick Seitz Materials Research Laboratory. "We are working actively with collaborators to explore possibilities in advanced health monitors, prosthetic devices and therapeutic systems.
Schepens Eye Research Institute - Regenerating the Human Retina
Many of the developments in virtual eyes are dedundant, if there is no reliable way to tie them in with a damaged retina - the termination of the optic nerve at the back of the eye. Howver, earlier this year, Schepens Institute publicised success with using stem cell therapy to do just that. Its a long way from regrowing a functional retina, but more than enough to recreate healthy nerve endings to bind to.
Researchers found a chemical compound that activates the progenitor cells already found in the eye. Progenitor cells are similar to stem cells but are more mature and are more limited in the number of cells types they can become.
?This study is very significant. It means it might be possible to turn on the eye?s own resources to regenerate damaged retinas, without the need for transplanting outside retinal tissue or stem cells,? said Dr. Dong Feng Chen, associate scientist at Schepens Eye Research Institute and Harvard Medical School, and the principal investigator of the study. ?If our next steps work in animal disease models, we believe that clinical testing could happen fairly quickly.?
They added each chemical separately to cultures of pure M?ller cells and injected each into the space below the retina in healthy mice. In both cases, the cells became progenitor cells and then changed into retinal cells. And with aminoadipate, the newly minted retinal cells migrated to where they might be needed in the retina and turned into desirable cell types. Specifically, they showed that by injecting the chemical below the retina, the cells give rise to new photoreceptors ? the type of cells that are lost in retinitis pigmentosa or macular degeneration, as a result, leading to blindness.