Kay Thornton became the first US patient to have her vision restored with the help of a tooth transplanted in her eye.

When you are blind and trying to restore your sight, you’ll try anything. I mean, anything. US doctors have recently returned a woman’s vision by using a transplanted tooth to help anchor a telescope in her eye. That’s right, a tooth. The procedure took several surgeries at Bascom Palmer Eye Institute in Miami, but it has given Kay Thornton her vision back after nine years of blindness. Check out the clip from NBC Today Show (via Hulu) after the break, apologies for the commercial.

Part of what is remarkable about this surgery is that it’s actually more than 40 years old. Modified osteo-odonto keratoprosthesis (MOOKP) was developed in Italy in the 1960s. It’s been performed around 600 times worldwide, but Thornton is the first US patient. Unlike corneal transplants, MOOKP does not require donor matching as all the tissue comes from the patient herself.

Unlike the other telescope implants we’ve discussed, the MOOKP telescope is simply correcting corneal damage. The rest of the eye is healthy. In Ms. Thornton’s case, the cornea was scarred due to lack of moisture stemming from Stevens-Johnson syndrome.

As described in the video, the MOOKP procedure takes place in several parts. First, a tooth and section of the jaw is removed and filed down to hold the telescope. The assembly is planted under the skin for a period and a skin graft from the cheek is placed over the eye. This step allows the tooth bone to bind to the telescope, and for the skin graft to keep the eye moist.

The tooth is then extracted and placed on the eye (allowing the telescope to pass light onto the retina) and the skin graft covers the eye again to keep everything lubricated. The graft can be further covered by a cosmetic shell (shown in the video diagram). It appears Thornton is not using a shell at this time as you can see the fleshy pink graft in some of the video.

MOOKP has never been used in the US due to its lack of testing and concerns over safety. Corneal transplants have taken its place for a majority of prospective patients. I’m not sure whether Thornton’s case is a special one, or if the Miami based surgical team will continue to perform the procedure. There seem to be few risks associated with the technique beyond tooth loss and the general risks assigned to corneal surgery.

Perhaps the big lesson here is that good surgeries never die. When a medical technique is extreme and strange, it has a low chance for widespread adoption. Still, if the procedure works, and it can’t be done in a different way, it will eventually develop a following. 600+ patients have tried to restore sight with the help of a tooth, and now that the US has a success to point to, that number could climb even higher. It makes you wonder what other procedures have waited 40 years to make it to the US, or the world,  and how we might be benefit if they saw wider use.

The macula is a part of the retina responsible for highly detailed central vision. It contains a high density of cone cells, which allow us to perceive fine detail and quick movement in our environment – for healthy individuals, that is. Patients suffering from age-related macular degeneration (AMD) partially or totally lose this functionality, resulting in a “blind spot” where their focal point normally rests. This can make it difficult to read, recognize faces, or even watch television… until now.

The Implantable Miniature Telescope, or IMT, is a tiny prosthetic implanted into the patient’s eye. Rather than directing light to the damaged macula, the telescope projects the image onto a broader surface of the retina that surrounds the macula. In this way, visual information is redirected to healthy rods and cones, and can be processed in the brain as central vision.

Both central and peripheral vision are important functions of the visual system. Because of this, the IMT is only implanted into one eye of patients with macular degeneration. One eye continues to process peripheral vision normally (which is better suited for low-light vision, for example), while the implanted eye restores the central vision that was previously impaired. This allows individuals to again experience the full range of visual stimuli so necessary to everyday life.  And because the implant is embedded in the iris, it goes unnoticed to others.

Macular degeneration primarily effects older adults, and is the leading cause of blindness in the elderly. Nearly 15 million people suffer from AMD in the United States alone. Approximately 10% of adults between the ages of 66 and 74 suffer from AMD, a figure that jumps to 30% between the ages of 75 and 85, according to The Eye Digest.

“In an end-stage AMD population, the indicated improvements in this study are substantial compared to risks of surgery,” said study coauthor R. Doyle Stulting, M.D., Ph.D. “For patients with this level of visual impairment, the ability to be less dependent on others and to reclaim even a few of the activities they once enjoyed could make a real difference in their lives.”

The IMT was developed by VisionCare Ophthalmic Technologies, and the implant has recently completed Phase II/III clinical trials. The tests showed that the IMT doubled the vision of 2/3 of participants’ eyes (3 lines on a visual acuity chart) after one year with the implant.  Some patients experienced side effects like intraocular pressure and inflammation, though these may have been related to the surgury.  On March 27, an advisory panel for the Food and Drug Administration (FDA) unanimously recommended the prosthetic for approval. Barring any unforeseen events, the IMT will soon gain FDA approval and hit the market soon thereafter.

While the IMT is certainly an amazing breakthrough, it is just one of many technologies we’ve reported on that are overcoming blindness (such as bionic eyes and gene therapy).  Besides the direct clinical application of such amazing technology, eye implants beg the question of how far these kinds of advances will go. Who knows? Maybe your grandkids will sport bionic eyes capable of zooming, night vision, and infrared perception. Regardless, anatomical prosthetics like the IMT promise to improve individuals’ lives today, and lay the theoretical foundation for exciting technology to come.

The patients in the study suffer from Leber’s congenital amaurosis (LCA), a rare inherited eye disease caused by a defective gene called RPE65. The condition appears at birth or in the first few months of life and causes progressive deterioration in vision.  Until now there have been no effective treatments available.

Below is an excellent “must watch” video from CBS documenting this amazing breakthrough, followed by further details and comments:

Normally, cells in the eye activate the RPE65 gene to produce an enzyme necessary for the function and health of a protective layer of cells underlying light- and color-detecting photoreceptor cells in the eye.  Patients with a defective RPE65 gene are unable to produce this enzyme, leading to photoreceptor cells that are otherwise healthy but unable to do their job.  Over many years the photoreceptor cells themselves steadily become damaged beyond repair.

Researchers theorized that if they could “upgrade” these photoreceptor cells with the non-defective gene then damage to the photoreceptor cells would cease and any remaining healthy cells would regain their ability to function.  A virus was used to inject the functioning gene into the target cells and within a week vision improved and remained so after 90 days — the study’s endpoint.

In theory, the younger the patient, the better this therapy will work because the degenerative nature of the disease will have had less time to cause permanent destruction to photoreceptor cells.  Trials are now underway with younger patients and the researchers are hopeful that these younger patients will see substantial, perhaps even full recovery of vision.

Wired has an excellent review of this story.  A few excerpts:

Though the trial was designed to test the therapy’s safety rather than its efficacy, its benefits were so impressive that the researchers decided to publicize their results.

“One of the patients said that the dim red light from his alarm clock had gotten so bright that it bothered him,” said Artur Cideciyan, a University of Pennsylvania opthamologist and co-author of the study. “He had to turn away from it while he was sleeping.”

Cideciyan’s study, published today in the Proceedings of the National Academy of Sciences, is one of three simultaneous trials of gene therapy for Leber’s Congenital Amaurosis, also known as LCA. Results from the first two were published in April in the New England Journal of Medicine:

Much more detail can be gathered at the following links:

http://www.ucl.ac.uk/ioo/research/patients/clinical_trials.html

http://www.ucl.ac.uk/ioo/research/patients/clinical_trials_furtherinfo.html

http://www.pnas.org/content/102/17/6177.full.pdf

A company called Second Sight Medical Products in partnership with a large consortium headed by the Department of Energy is currently testing its second generation model, called the Argus II, on more than 20 individuals.  Patients that were completely blind are able to see moving objects, read very large print, and recognize several other visual cues once implanted with the Argus II artificial retina.  From the article:

A patient named Terry spotted the shadow of his 18 year-old son as he passed
by on a sidewalk. “It was the first time I’d seen anything of him since
he was 5 years old,” Terry told Artificial Retina News, a publication
of the Artificial Retina Project.

The third generation model is already in the works and promises much better vision by interfacing with the brain using a 1,000 electrode array vs the 60 electrode array used in the Argon II.

These artificial retinas are still years away from becoming widespread because they are too expensive, too clunky, and too fragile to withstand decades of normal wear and tear.  Yet all of these problems are being addressed aggressively and soon millions of blind people will be given back the gift of sight.  Amazing!

Above: The Argus II Artificial Retina System

Although Second Sight Medical Products is the private sector company producing the Argus II, the real force behind this awesome product is an initiative from the U.S. Department of Energy called the Artificial Retina Project.  From the Artificial Retina Project website:

The Artificial Retina Project is a collaborative, multi-institutional effort to develop an implantable microelectronic retinal device that restores useful vision to people blinded by retinal diseases. The ultimate goal of the project is to restore reading ability, facial recognition, and unaided mobility in people with retinitis pigmentosa and age-related macular degeneration.

According to this more technical article, the artificial retina, also known as a retinal prosthetic, works as follows:

1. A pair of glasses with a small video camera is worn by the patient
2. The video captured by the camera is sent wirelessly to a belt pack containing a microprocessor that processes the video signal
3. This processed video signal is sent to an antenna in the eye
4. The antenna is connected to an array of electrodes that have been implanted directly inside the eye on top of the old retina
5. The array of electrodes transmits signals that directly stimulate optic nerve cells that are responsible for sending images to the brain’s vision centers