Synthetic Eye Prosthesis

"Donor corneas are a rarity: In Germany alone, each year roughly 7,000 patients wait for that miniscule piece of tissue. An implant made of plastic may soon offer patients - especially those facing their last resort - with the chance to see again.

For many patients who become blind after an accident or illness, a corneal transplantation could restore the ability to see. Each year, 40,000 people in Europe - in Germany, about 7,000 - await the opportunity to be able to see again, thanks to cornea donors. But donor corneas are not common. Dr. Joachim Storsberg of the Fraunhofer Institute for Applied Polymer Research IAP in Potsdam-Golm developed material and production process for a corneal prosthesis made of plastic. These can help patients who are unable to tolerate donor corneas due to the special circumstances of their disease, or whose donor corneas were likewise destroyed. In recognition of this accomplishment, Dr. Storsberg is being awarded the 2010 Joseph von Fraunhofer Prize.

The miniscale artificial cornea has to meet almost contradictory specifications: On the one hand, the material should grow firmly together with the cells of the surrounding tissue; on the other hand, no cells should settle in the optical region of the artificial cornea - i.e., the middle - since this would again severely impair the ability to see. And: The outer side of the implant must be able to moisten with tear fluids, otherwise the implant will cloud up on the anterior side. This would consequently require the patient to get a new prosthesis after a relatively brief period of time. And: The outer side of the implant must be able to moisten with tear fluid, so that the eyelid can slide across it without friction. Dr. Storsberg found the solution with a hydrophobic polymer material. This material has been in use for a long time in ophthalmology, such as for intraocular lenses. In order for it to satisfy the various characteristics required, complex development steps were necessary. The material was thoroughly modified on a polymer-chemical basis, and subsequently re-tested for public approval.

In order to achieve the desired characteristics, the edge of the implant was first coated with various, special polymers. Then, a special protein was added that contains the specific sequence of a growth factor. The surrounding natural cells detect this growth factor, are stimulated to propagate and populate the surface of the corneal margin. Thus, the cells of the surrounding tissue grow with the implant, and the artificial cornea attains stability. The eye prosthesis evolved jointly with physicians and manufacturers in the EU project, „Artificial Cornea." The interdisciplinary research team needed three years to develop the artificial cornea. In a first step, they sent the chemical-biomimetic coated implant to Dr. Karin Kobuch of the Poliklinik für Augenheilkunde at the Regensburg University Medical Center and to the medical center at the Technical University of Munich, on the right banks of the Isar river. The physician examined the artificial corneas in dissected pigs eyes and specialized cell cultures. Eventually, the team under Dr. Gernot Duncker and Dr. Saadettin Sel of the University Center for Ophthalmology in Halle (Saale) tested the more complex models in rabbits. There, the design was further refined: the optics were made smaller, and the implant haptic enlarged in order to maintain a more stable construction. Miro GmbH manufactured the implant, robin GmbH handled the distribution and sales and supported the specially adapted implantation centers in Europe. By 2009, a prosthesis was already successfully in use; further implantations are anticipated during the first six months of 2010."

~ Source: MedicalNewsToday.com

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New Procedure Has Sights Set on Eye Cancer

"An ophthalmologist at Washington University School of Medicine in St. Louis is implanting radioactive discs in the eyes of children with a rare cancer in an attempt to save their vision and their eyes.

J. William Harbour, MD, is one of only a few doctors nationwide to use the approach for treating a rare, childhood eye cancer, called retinoblastoma. Harbour, the Paul A. Cibis Distinguished Professor of Ophthalmology and Visual Sciences, performs the surgery at St. Louis Children's Hospital. He implants a small disc, or plaque, which stays in the eye for three days before a second surgery to remove it.

"The standard of care for retinoblastoma is chemotherapy, followed by laser and freezing treatments to eliminate the last remnants of tumors," Harbour says. "But occasionally there will be a tumor that doesn't respond to chemotherapy or is too large to treat with a laser or freezing treatment. That's where this plaque treatment comes in. It gives us an option that may allow us to save the eyes of a young child."

Retinoblastoma, as the name suggests, is characterized by tumors in the eye's retina. It is extremely rare, affecting about one child in 20,000. In the United States, about 200 children each year are diagnosed with retinoblastoma. Approximately 40 percent of them develop tumors in both eyes, so in cases where the tumors prove resistant to chemotherapy, very young children and their parents are faced with a choice between a life without eyes and a high risk of death.

That's why Harbour, also a professor of cell biology and of molecular oncology and director of ocular oncology at the Siteman Cancer Center at Barnes-Jewish Hospital and Washington University School of Medicine, and a handful of other eye cancer specialists have recently started using the plaque method to treat the cancer and possibly save the eyes.

"The treatment plaque looks like a bottle cap made of gold," Harbour says. "Radiation seeds are placed on one side of the plaque, shining the radiation in one direction like a flashlight focused on the tumor. That prevents the radiation from affecting other parts of the body."

The plaques contain seeds that deliver radiation directly to the tumor cells. Harbour says because the radiation gets to the tumor in a much more focused way than was possible in the past, it is not likely that these plaques will contribute to future problems in or around the eye.

Implantation of radioactive plaques has been relatively common in adult patients with a different eye cancer called ocular melanoma. The gold discs have been the standard of care for those patients for decades, and results to date in an ongoing National Institutes of Health (NIH) study have demonstrated that the plaques are an effective treatment in adults with ocular melanoma.

Although the NIH study showed that plaque therapy is as effective as eye removal in preventing the spread of ocular melanoma, the small number of children who have retinoblastoma make it unlikely a similar study could be conducted for that form of eye cancer. He estimates only about 10 to 20 children per year will require the plaque therapy in the United States. " ~ Source: MedicalNewsToday.com

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High Altitude Affects Cornea but Not Vision in Study

"ZURICH, Switzerland, March 2010 — Mountain climbing at high altitudes can cause swelling of the cornea but does not appear to affect vision, according to a new study.

Study results show that, at high altitudes, a decrease in oxygen can cause mountain sickness and cornea changes.

Researchers at the University Hospital Zurich, Switzerland, studied 28 volunteers who climbed Mount Muztagh Ata in western China. Participants reached about 6,300 meters or 20,670 feet.

One group of climbers had less time to acclimate before ascending. The researchers studied the climbers' corneal thickness, visual acuity and blood oxygen levels before, during and after ascent.

In both groups, corneal thickness and blood oxygen levels increased as the altitude increased; they decreased after descent. The researchers also found a correlation between corneal thickness and mountain sickness.

The group that had less time to acclimate had a greater increase in corneal thickness.

Altitude did not affect visual acuity significantly in either group.

The researchers noted that although vision was not affected at 6,300 meters, more extreme altitudes may cause damage to the cornea that could potentially lead to vision loss." ~ Source: AllAboutVision.com

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Green Tea May Protect Against Eye Diseases

"New research from Hong Kong suggests that green tea may protect against eye diseases such as glaucoma because the researchers found green tea antioxidants called catechins present in various tissue structures in the eyes of laboratory rats after they had ingested green tea.

The researchers, based at Hong Kong Eye Hospital, Kowloon, and the Prince of Wales Hospital, Shatin, in the New Territories, Hong Kong, have written about their findings in a paper that appeared in the 10th February print issue of the American Chemical Society's bi-weekly Journal of Agricultural and Food Chemistry.

Green tea contains catechins which belong to the family of antioxidants that includes vitamin C, vitamin E, lutein, and zeaxanthin and is well-known for its disease-fighting properties.

Until this study, however, nobody knew if green tea catechins actually passed from the stomach and gastrointestinal tract into the tissues of the eye.

For their investigation Dr Chi Pui Pang, of the Hong Kong Eye Hospital, and colleagues examined the eyes of dead rats that had been fed green tea extract for varying amounts of time.

When they examined the cornea, lens, retina, choroid-sclera, vitreous humor, and aqueous humor, they found evidence that these various eye structures had absorbed significant amounts of individual catechins.

For example, the retina absorbed the highest levels of gallocatechin and the aqueous humor absorbed epigallocatechin.

They also found that the time of maximum concentration of the catechins varied from 0.5 to 12.2 hours and their effects in reducing harmful oxidative stress in the eye lasted for up to 20 hours after consumption.

Chi Pui Pang and colleagues concluded that: "Our results indicate that green tea consumption could benefit the eye against oxidative stress."

However, more studies are needed to verify the same effects occur in humans." ~ Source: MedicalNewsToday.com

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Artificial Eye Muscles?

(SACRAMENTO, Calif.) — Eye Surgeons from UC Davis Medical Center have demonstrated that artificial muscles can restore the ability of patients with facial paralysis to blink, a development that could benefit the thousands of people each year who no longer are able to close their eyelids due to combat-related injuries, stroke, nerve ierve injury or facial surgery.

In addition, the technique, which uses a combination of electrode leads and silicon polymers, could be used to develop synthetic muscles to control other parts of the body. The new procedure is described in an article in the January-February issue of the Archives of Facial Plastic Surgery.

"This is the first-wave use of artificial muscle in any biological system," said Travis Tollefson, a facial plastic surgeon in the UC Davis Department of Otolaryngology – Head and Neck Surgery. "But there are many ideas and concepts where this technology may play a role."

In their study, Tollefson and his colleagues were seeking to develop the protocol and device design for human implantation of electroactive polymer artificial muscle (EPAM) to reproducibly create a long-lasting eyelid blink that will protect the eye and improve facial appearance. EPAM is an emerging technology that has the potential for use in rehabilitating facial movement in patients with paralysis. Electroactive polymers act like human muscles by expanding and contracting, based on variable voltage input levels. ~ ScienceDaily.com