Laser instead of scalpel

Perfect eye cut
Russian physicists and ophthalmologists are developing a scalpel of the XXI century, which will cut tissue without damageAlla Astakhova, the magazine "Results" No. 17-2009

In a semi-dark room of the Center for Physical Instrumentation of the Institute of General Physics of the Russian Academy of Sciences in Troitsk, work is in full swing. Researchers are in a hurry to complete testing of the new device. Now its optical and electronic "fillings" are neatly laid out on the table. However, very soon the device will be tested for the first time by a doctor, and physicists will continue to work closely with him. On the recommendation of doctors, they will invent more and more new modifications of the device. As experience shows, only the sixth or seventh option will be really suitable. However, researchers are already using a laser to draw patterns inside the glass. Subsequently, the same complex lines of almost any configuration will be able to output an ophthalmologist surgeon. First in the eye tissues of animals, and then, after lengthy tests, in humans. According to scientists, the surgical instrument of the future – the femtosecond laser, which Russian physicists and ophthalmologists are currently working on, is already on the way. It's just right to call it the perfect scalpel. After all, he is able to work where it is necessary, without damaging the tissues located outside.

Fine workThe glow of the laser is not visible, because it works in the infrared range, but the result of the work is obvious – rows of microscopic dots in the glass forming lines of ideal shape.

In the same way, everything will happen inside the eye. Why only inside and not outside? Sophisticated optics and electronics allow laser beams to be focused in such a way that they reach maximum intensity not on the surface, but at a depth of several hundred microns. For this purpose, a special laser wavelength has been selected, approximately 1060 nanometers. Each dot that appears in the glass corresponds to a laser flash that lasts several hundred femtoseconds, that is, quadrillionths of a second. This is much less than the lasers of the previous generation: there, the duration of the flash was calculated in nanoseconds, billionths of a second. Why do scientists need a race against time? "It's simple," explains Konstantin Lapshin, head of the Femtosecond Laser Keratome project at the Center for Physical Instrumentation at the Institute of General Physics of the Russian Academy of Sciences. "A femtosecond laser has two advantages. Firstly, if the pulse is very short, the heat from the flash does not have time to be transmitted to the surrounding tissues. Secondly, and this is also very important, the laser with ultrashort flashes has a high power density. It is from this density that the effect of the laser on the substance depends. As a result, specialists can work with very low energies. To achieve the desired effect, we need only about half a watt of power – much less than that of the microscopic light bulb itself. This is important, because high energies can simply damage the eye."

All lasers of previous generations, which ophthalmologists used in their work, caused tissue burns to one degree or another. "Of course, laser damage is hundreds of times more delicate than a burn with a hot iron," says Hristo Takhchidi, General Director of the S. N. Fedorov Federal State University of Eye Microsurgery. – But the biological manifestation of the burn is the same: subsequently, microscopic scars may form. This is very important for the tissues of the eye, because a person is able to feel the slightest changes in it even before they are registered by devices. Just a few microns, which we have won from the disease, can dramatically improve or, if it is the opposite, worsen vision." In the case of a femtosecond laser, there is no burn and subsequent scars – when it works, a process occurs in the cells that can be compared to a micro-explosion, they break up into water and gas, mechanical tissue stratification occurs. The laser beam enters the eye like the most delicate scalpel, cutting through an incredibly thin and even line. The error in laser surgery can be reduced to just a few microns.

The use of the "perfect scalpel" promises a breakthrough in the technique of operations. For example, now a corneal transplant (this is several thousand operations per year) can cause a lot of trouble to the patient and doctors. Today, it is almost impossible to "adjust" the shape and thickness of the transplanted donor cornea during transplantation to the surface of the eye, from which the same piece is cut off before that. Therefore, serious visual impairments have become a common occurrence during transplantation. They have to be corrected surgically. However, the "perfect scalpel" can not only cut tissue along the most intricate line. With its help, it will even be possible to apply a kind of "cutting" to the side of the thinnest flap with a thickness of 100 microns. At the same time, the transplanted donor insert will securely "twist", like a screw, into the surface of the patient's eye.

Refractive surgery will be different. Now, in order to correct farsightedness or myopia with a laser, surgeons first "draw" a lid on the surface of the eye, then "sharpen" the cornea, correcting its shape. But in the future, the "lid" may simply not be needed. However, the most radical changes are expected in the technique of lens transplantation. "We are already thinking about a new operation," says Hristo Takhchidi. – With the help of a laser, we will be able to "get" the lens, which is located in the eye at a depth of several millimeters. By focusing laser beams on it, we will vaporize it right in the eye, turning it into gas bubbles and water. Then we will remove the contents through the thinnest tube and "fill" the remaining cavity with a special liquid. When it hardens, it will give us a new lens. I promise: one day it will be possible to "seal" the eye, as we are now filling the teeth."

Technical issueThe competition for the right to create a surgical instrument of the future – a femtosecond laser "scalpel" – has been going on in the world for more than a decade.

Specialists from the USA were the first to shoot their development at the end of the 90s of the last century. However, the quality of their invention then impressed few. "I remember when I first saw a femtosecond laser for ophthalmology, I was surprised: why is this necessary? – says the head of the department of refractive laser surgery of the FSU MNTC "Eye Microsurgery" named after S. N. Fedorov, the famous ophthalmic surgeon Yuri Kishkin. – Then this laser worked pretty rough. Due to the design features, he could only make large "dots" in the fabric, he rarely put them, so the line between them was torn. It became clear that a good doctor with a conventional scalpel will achieve better results. However, the development in this area has gone surprisingly fast. And today the advantages of laser operations are obvious."

In recent years, several more research teams from Switzerland, Germany and Russia have joined the race for results. There are now four different devices of this type in the world. However, experts admit: the ideal femtosecond system has not yet been created. "Each model has its drawbacks," says Sergey Vartapetov, Director of the Center for Physical Instrumentation at the Institute of General Physics of the Russian Academy of Sciences. Someone makes too much laser dot exposure inside the eye tissues, someone, on the contrary, "draws" perfect lines, but does not know how to focus the rays so that the "dots" appear at different depths. As a result, surgeons are forced to perform operations in several stages using different types of lasers.

But now Russian physicists and doctors are aiming for more. "The idea is in the air," says Konstantin Lapshin. – We are making a femtosecond system capable of "drawing" any lines inside the eye. The difficulty is to set up an optical beam focusing scheme and an electronic "stuffing". Since ophthalmic operations are performed only under local anesthesia, the speed of the operation is also critical. It should last no more than a few tens of seconds."

Of course, many surgeons would like to have such a tool in their arsenal. However, ophthalmologists were the first. "It so happened that many medical technologies of the XXI century were tested in our field," says Hristo Takhchidi. – We are aware of the importance of each micron, so the desire of ophthalmic surgeons to work in microstructures is understandable. But I think that gradually others will come to this."

Ophthalmologists who are confident in the new device are already thinking about the composition of the liquid for "filling" the eye. Taking into account the development of modern technologies, they promise to make a fairy tale come true in just five, maximum ten years. And to confirm that dreams come true, they cite a story that happened to the famous Svyatoslav Fedorov in the early 90s of the last century. Then his promise to make a soft artificial lens instead of the hard ones that were widely used was considered by many to be a fantasy. However, in 1996, the MNTC sold the license for a soft silicone lens to the Americans. And, by the way, it receives its legal eight percent of royalties until today, when dozens of companies around the world produce soft lenses. Of course, it's a pity that these lenses are not produced in Russia, but domestic technologists would hardly "hold out" the idea. And ophthalmologists seem to have been lucky with laser specialists. After all, this area is actively developing in Russia. In any case, the ultraviolet excimer laser, which was once created at the Institute of General Physics of the Russian Academy of Sciences in collaboration with Svyatoslav Fedorov, has become a successful development. Therefore, there is hope that the ideal femtosecond lasers for ophthalmic operations will appear here.

Portal "Eternal youth" www.vechnayamolodost.ru20.04.2009