TAU develops revolutionary technique to ‘solder’ newly transplanted corneas

Employing lasers, fiber optics, method eventually could be used on other organs.

By JUDY SIEGEL-ITZKOVICH
Eye exam [Illustrative] (photo credit: REUTERS)
Eye exam [Illustrative]
(photo credit: REUTERS)
Tel Aviv University researchers were able to transplant corneas and “solder” them in place on the eyes using advanced laser and fiber optic technology to eliminate the need to use sutures. The new technique improves vision and speeds recovery.
The technique used by doctors to heal the tissues essentially has not changed for thousands of years. The modern surgeon, just like his predecessors over the centuries, used to sew up the incision with needle and thread; the result is that the quality of the seam and the scar it leaves behind depend on his skills and experience of the physician.
Now Tel Aviv University researchers are offering a new method that would allow the surgeon to achieve an excellent result – fusing seamless tissue sections using a laser beam.
“The basic idea of fusing cuts by laser beam heating is not new, it was first raised in the 1960s,” said Prof. Abraham Katzir, head of the Applied Physics Group at the school of physics and astronomy. “Over the years, there have been many attempts to fuse the tissues, but most of them did not work. We believe we have found the key to successful: strict control over the temperature of the heated zone by the laser during tissue fusion.”
Katzir is the son of the late Prof. Aharon Katzir (Katchalsky), who was intended by then-prime minister Golda Meir to be president of Israel but was murdered in the 1972 Japanese Red Army terrorist massacre at Lod Airport. After his murder, Meir chose Prof.
Ephraim Katzir, his brother and also a scientist, and he was the fourth president between 1973 and 1978.
In 1977, Avraham Katzir established TAU’s Applied Physics Group. In a recent study, in collaboration with Dr. David Varssano of Tel Aviv Sourasky Medical Center and Dr. Irina Barkat from Sheba Medical Center at Tel Hashomer (and both having senior positions at TAU’s Sackler Faculty of Medicine), Katzir used the technique to transplant corneas taken from animals after their deaths.
The research was published recently in the journal Proceedings of the International Society for Optics and Photonics and has aroused much interest in the medical world around the world.
The reason for the failure of the eye tissues to fuse is the temperatures at which they are heated, said Katzir. “In this sense, fusion of the tissues is similar to heating a raw egg. If you heat it to 20 degrees Celsius, nothing with happen. If it is at 70 degrees, it will turn into a hard-boiled egg. At 200 degrees, the egg will burn.”
The exact temperature is therefore a critical factor in the whole process, but until now, in most studies of laser-fusion, temperature was not measured at all, nor taken into account.
“We hypothesized that the most suitable temperature for allowing the tissue to fuse optimally was 65 degrees Celsius – just like cooking a boiled egg,” Katzir said.
Based on this hypothesis, the researchers sought to develop a technology that allow the doctor to measure and control the temperature of tissues throughout the fusion process.
For this they were assisted by their team’s unique expertise – manufacturing optical fibers able to transmit infrared light.
“Our group is one of the few in the world that knows how to develop and produce special optical fiber that, unlike ordinary glass fiber, is able to transmit light that is invisible in the infrared spectrum,” explained Katzir. “Such fibers, made of crystal silver halides (the same material that used for old-style camera film – are nontoxic, water soluble and can be utilized for medical uses. Until now, we have used them in devices such as laser cutting of tissue during surgery and speedy thermometers that measure the body temperature from insertion in the external ear.”
Several years ago, TAU researchers developed a new technique to heal tissues, based on their unique knowledge, and integrated two special optic fibers – one delivered laser radiation that heated a dot on the tissue used for fusion, while the second, which was adjacent to the first, was used to measure the dot’s temperature. The control circuit make it possible to keep the optimal temperature of 65 degrees steady at the point of fusion. The two edges of the incision were attached to each other, and the points were heated one at a time so the tissue could fully heal. Thus there is a powerful fusion without thermal damage to the incision area.
This system was tested in the lab, first with dead tissues and later in live pigs. Among other things, the results were promising, as the incisions healed strongly, almost without scarring. Following the success, the Health Ministry approved human experimentation trials at Emek Medical Center in Afula, and two surgeons – Prof. Doron Kopelman and Dr. David Simhon – used the technique to splice the incisions that remained in skin of the abdomen after laparoscopic surgery to remove the gallbladder.
Once again, the technique produced “good looking” fusing with minimal scarring.
To improve the method, the researchers innovated again – they combined both functions – heating tissues and optical temperature measurement – into one. “When there’s only one fiber, the surgeon’s hand movements do not affect the measurements, and the success rate rises significantly,” said Katzir.
Varssano and Barkat tested and improved the technology on eyes taken from cows and returned after their death. They took some of the cornea, put it back in its original place and then injected water into the eye. They created pressure triple the amount in that is in normal eyes. The results was that the transplanted corneas were very stable and did not move out of place. In addition, water did not leak from the fused tissue, and there was no thermal damage to the cornea.
“Now we are waiting for approval to perform corneal transplant surgery on live pigs, and later in humans,” said Katzir.
“Currently, using the old technique of sewing the cornea, very precise stitches are needed by a skillful surgeon. When the suturing is not completely symmetrical, the patient’s vision can be damaged, and crude stitches can cause pain in the long term. We believe our new technique will allow less-experienced doctors to carry out accurate and successful cornea transplantation.”
Down the road, the researchers predicted many more uses for the new technology, based on a single optic fiber, including fusing brain tissue and internal organs, microsurgery of tiny blood vessels, surgery inside the body using robotic systems, emergency medicine and surgery in the battlefield, plastic surgery, ear-nose-andthroat procedures in young children and more. “In fact, anywhere in the body where the surgery is done, it will be possible to achieve in this way seamless fusion with minimal scarring,” he concluded.