excimer laser. Excimer and femtosecond lasers

In this article, we will consider the advantages of excimer lasers. Today, medicine has a wide range of all kinds of laser equipment for the treatment of complex diseases in hard-to-reach areas of the human body. help to achieve the effect of minimally invasiveness and painlessness, which has a huge advantage over those surgical interventions that are performed manually during abdominal operations, which are very traumatic, fraught with high blood loss, as well as long-term rehabilitation after them.

What is a laser?

A laser is a special quantum generator that emits a narrow beam of light. Laser devices open up incredible possibilities for transmitting energy over different distances at high speed. Ordinary light, which is capable of being perceived by human vision, is a small beams of light that spread in different directions. If these beams are concentrated using a lens or a mirror, a large beam of light particles will be obtained, but even this cannot be compared with a laser beam, which consists of quantum particles, which can only be achieved by activating the atoms of the medium that underlies laser radiation.

Varieties

With the help of the colossal developments of scientists around the world, excimer lasers are now widely used in many areas of human activity and have the following varieties:

Origin

This variety is ultraviolet, which is widely used in the field of eye surgery. With the help of this device, doctors perform laser vision correction.

The term "excimer" means "excited dimer" and characterizes the type of material that is used as its working fluid. For the first time in the USSR, such a device was presented in 1971 by scientists V. A. Danilichev, N. Basov and Yu. M. Popov in Moscow. The working body of such a laser was a xenon dimer, which was excited by an electron beam in order to obtain radiation with a certain wavelength. After some time, noble gases with halogens began to be used for this, and this was done in 1975 in one of the US research laboratories by scientists J. Hart and S. Searles.

People often ask why an excimer laser is used for vision correction.

Its uniqueness

It was found that the excimer molecule produces due to the fact that it is in an excited "attractive" state, as well as in a "repulsive" state. This action can be explained by the fact that xenon or krypton (noble gases) have a high inertness and, as a rule, never form chemical compounds. An electrical discharge puts them in an excited state, as a result of which they can form molecules either among themselves or with halogens, for example, chlorine or fluorine. The appearance of molecules in an excited state creates, as a rule, the so-called population inversion, and such a molecule gives up its energy, which is stimulated or spontaneous emission. After that, this molecule returns to the ground state and breaks up into atoms. The excimer laser device is unique.

The term "dimer" is usually used when the same atoms are connected to each other, however, compounds of noble gases and halogens are used in most modern excimer lasers. Nevertheless, these compounds, which are used for all lasers of this design, are also called dimers. How does an excimer laser work? This is what we will now consider.

The principle of operation of the excimer laser

This laser is the main protagonist of PRK and LASIK. Its working fluid is an inert and halogen gas. When a high voltage is introduced into the mixture of these gases, one halogen atom and one inert gas atom combine to form a diatomic molecule. It is in a highly excited state and after a thousandth of a second it decays into atoms, which leads to the appearance of a light wave in the UV range.

This principle of operation of the excimer laser has found wide application in medicine, since ultraviolet radiation affects organic tissues, for example, the cornea, in such a way that the bonds between molecules are disconnected, leading to the transfer of tissues from a solid to a gaseous state. This process is called "photoablation".

Wave range

All existing models of this type operate in the same wavelength range and differ only in the width of the light beam, as well as in the composition of the working fluid. The excimer laser is the most commonly used for vision correction. But there are other areas of its use.

The former had a light beam diameter that was equal to the diameter of the surface on which the evaporation took place. The wide range of the beam and its inhomogeneity caused the same inhomogeneity of the upper layers of the cornea, as well as an increase in temperature on its surface. This process was accompanied by injuries and burns. This situation was corrected by the creation of an excimer laser. The MNTK "Eye Microsurgery" has been using it for a very long time.

New generation lasers have undergone a long process of modernization, during which the diameter of the light beam has been reduced, and a special rotational-scanning system for delivering laser radiation to the eye has also been created. Consider how excimer lasers are used by doctors.

Application in medicine

In cross section, such a laser beam looks like a spot moving in a circle, removing the upper layers of the cornea, as well as giving it a different radius of curvature. In the ablation zone, the temperature does not rise, since the effect is short-term. As a result of the operation, a smooth and clear surface of the cornea is observed. The excimer laser is indispensable in ophthalmology.

The surgeon performing the surgical intervention determines in advance what portion of the energy that will be supplied to the cornea, and also to what depth the excimer laser will be exposed. From here, the specialist can plan the course of the process in advance and assume what result will be obtained as a result of the operation.

Laser vision correction

How does an excimer laser work in ophthalmology? The technique popular today is based on the so-called computer reprofiling of the cornea, which is the main optical lens of the human eye. The excimer laser, which acts on it, smoothes the surface of the cornea, removing the upper layers and, thus, eliminating all defects present on it. In this case, normal conditions appear for obtaining the correct images by the eye, creating the correct refraction of light. People who have undergone such a procedure see as everyone who has initially good vision.

The procedure for reshaping the cornea does not cause high temperatures on its surface, which can be detrimental to living tissues. And, as most people believe, there is no so-called burning of the upper layers of the cornea.

The most important advantage of excimer lasers is that their use for vision correction allows you to get an ideal result and correct almost all existing corneal anomalies. These devices are so precise that they allow for "photochemical ablation" of the upper layers.

For example, if this process is carried out on the central zone of the cornea, then its shape becomes almost flat, and this helps to correct myopia. If the layers of the cornea in the periphery zone evaporate during vision correction, then its shape becomes more rounded, and this, in turn, corrects farsightedness. Astigmatism is corrected by dosed removal of the upper layers of the cornea in its various parts. Modern excimer lasers, which are widely used in refractive eye microsurgery, guarantee the high quality of the surface that is subjected to photoablation.

Features of use in medicine

Excimer lasers in the form they have today appeared quite recently, but now they help people all over the world to get rid of such vision problems as myopia, hyperopia, astigmatism. Such a solution to the problem, for the first time in many years of creating such equipment, meets all the requirements of painlessness, maximum safety and efficiency.

Diseases of the eye that are treated with

The field of ophthalmic surgery that deals with the elimination of these anomalies of the human eye is called refractive surgery, and such disorders are called ametropia and refraction anomalies.

According to experts, there are two types of refraction:

Ametropia, in turn, includes several subspecies:

myopia (nearsightedness);
astigmatism - obtaining a distorted image by the eye, when the cornea has an irregular curvature, and the flow of light rays becomes uneven in different parts of its surface;
hypermetropia (farsightedness).

Astigmatism is of two types - hypermetropic, which is close to farsightedness, myopic, similar to myopia and mixed.

In order to correctly present the essence of refractive manipulations, it is necessary to know the anatomy of the human eye minimally. The optical system of the eye consists of three main elements - the cornea, the lens, which are the light-refracting parts, and the retina, which is the light-perceiving part. In order for the resulting image to become clear and sharp, the retina is in focus of the ball. However, if it is in front of the focus, which happens with farsightedness, or behind it, which happens with myopia, the resulting image becomes fuzzy and significantly blurred.

In humans, the optics of the eye can change throughout life, in particular, from the moment of birth and up to 16-20 years, it changes due to the growth and increase in the size of the eyeball, as well as under the influence of some factors that can lead to the formation of certain anomalies . Thus, the patients of the eye refractive surgeon most often are adults.

Contraindications for Excimer Beam Vision Correction

Vision correction with an excimer laser is not indicated for all people suffering from visual impairments. The prohibition on the use of this procedure are:

Possible complications after application

All existing methods of treatment with an excimer laser today are highly safe and especially effective. However, there are a number of complications that can occur after surgery using these techniques. These include:

Partial or incorrect growth of a part of the cornea, after which it is not possible to grow this part again.
The so-called dry eye syndrome, when the patient has redness and pain in the eye. This complication can occur in cases where the nerve endings that are responsible for the production of tears have been damaged in the process of vision correction.
A variety of visual disorders, for example, double vision or decreased vision in the dark, impaired perception of colors or the appearance of a light halo.
Weakening or softening of the cornea, which can occur both a few months after surgery, and after a few years.

Excimer laser in dermatology

The effect of a low-frequency laser on the skin is extremely positive. This is due to the following effects:

anti-inflammatory;
antioxidant;
anesthetic;
immunomodulatory.

That is, there is a certain biostimulating mechanism of action of laser radiation with low power.

Vitiligo is being successfully treated with an excimer laser. Pigmented spots on the skin are very quickly smoothed out.

Working on electronic transitions of excimer molecules (molecules that exist only in electronically excited states). Potential dependence. the energy of interaction of atoms of an excimer molecule, which is in the ground electronic state, on the internuclear distance is a monotonically decreasing function, which corresponds to the repulsion of nuclei. For the excited electronic state, which is the top level of the laser transition, this dependence has a minimum, which determines the possibility of the existence of the excimer molecule itself (Fig.). The lifetime of an excited excimer molecule is limited

Dependence of the energy of an escimer molecule on distance R between its constituent atoms X and Y; the upper curve is for the upper laser level, the lower curve is for the lower laser level. The values correspond to the center of the active medium amplification line, its red and purple borders. time of its radiation. decay. Because the lower the state of the laser transition in E. l. is emptied as a result of the expansion of the atoms of the excimer molecule, the characteristic time to-rogo (10 -13 - 10 -12 s) is much less than the radiation time. empty top, laser transition states, the gas containing excimer molecules is active medium with amplification at transitions between the excited bound and ground expansion terms of the excimer molecule.

The basis of the active medium E. l. usually make up diatomic excimer molecules - short-lived compounds of atoms of inert gases with each other, with halogens or with oxygen. Wavelength of radiation E. l. lies in the visible or near UV region of the spectrum. The width of the amplification line of the laser transition E. l. is anomalously large, which is associated with the expansion nature of the lower transition term. The characteristic values of the parameters of laser transitions for the most common E. l. presented in the table.

Parameters of excimer lasers

Optimal parameters of the active medium E. l. correspond to the optimal conditions for the formation of excimer molecules. Naib, favorable conditions for the formation of inert gas dimers correspond to a pressure range of 10–30 atm, when such molecules are intensively formed in triple collisions involving excited atoms:

At such high pressures, the most eff. the method of introducing pump energy into the active medium of the laser is associated with the transmission of a beam of fast electrons through the gas, which lose energy predominantly. to the ionization of gas atoms. Conversion of atomic ions into molecular ions and subsequent dissociative recombination of molecular ions accompanied by the formation of excited atoms of an inert gas, provide the possibility of eff. conversion of the energy of a beam of fast electrons into the energy of excimer molecules Lasers based on inert gas dimers are characterized by an efficiency of ~1%. Main The disadvantage of lasers of this type is the extremely high value of beats. threshold energy input, which is associated with the short wavelength of the laser transition and, hence, the width of the gain line. This imposes high requirements on the characteristics of the electron beam used as a laser pump source and limits the values of the output energy of laser radiation to fractions of J (per pulse) at a pulse repetition rate of no more than a few. Hz. A further increase in the output characteristics of inert gas dimer lasers depends on the development of the technology of electron accelerators with an electron beam pulse duration on the order of tens of nsec and a beam energy of ~kJ.

Significantly higher output characteristics are distinguished by E. l. on monohalides of inert gases RX*, where X is a halogen atom. Molecules of this type are effectively formed in paired collisions, for example, or

These processes proceed with sufficient intensity already at pressures of the order of atmospheric pressure, so the problem of introducing energy into the active medium of such lasers turns out to be technically much less complicated than in the case of lasers based on inert gas dimers. Active medium E. l. on monohalides of inert gases consists of one or several. inert gases at a pressure of the order of atmospheric and a certain number (~ 10 -2 atm) of halogen-containing molecules. To excite the laser, either a beam of fast electrons or a pulsed electric beam is used. discharge. When using a beam of fast electrons, the output energy of laser radiation reaches values of ~ 10 3 J at an efficiency of several times. percent and a pulse repetition rate well below 1 Hz. In case of using electric discharge, the output energy of laser radiation per pulse does not exceed a fraction of J, which is associated with the difficulty of forming a discharge that is uniform in volume in, therefore, volume at atm. pressure over time ~ 10 ns. However, when using electric the discharge achieves a high pulse repetition rate (up to several kHz), which opens up the possibility of a wide practical. use of this type of laser. Naib. widespread among E. l. received a XeCl laser, which is due to the relative simplicity of the implementation of work in the high pulse repetition rate mode. cp. the output power of this laser reaches the level of 1 kW.

Along with high energy characteristics An important attractive feature of E. l. is an extremely high value of the active transition amplification linewidth (Table). This opens up the possibility of creating high-power lasers in the UV and visible ranges with smooth wavelength tuning in a fairly wide spectral region. This problem is solved with the help of an injection laser excitation circuit, which includes a low-power generator of laser radiation with a wavelength tunable within the width of the amplification line of the EL active medium, and a broadband amplifier. This scheme makes it possible to obtain laser radiation with a linewidth of ~10 -3 HM, tunable in wavelength in a range of ~10 HM and more.

E. l. are widely used due to their high energy. characteristics, short wavelength and the possibility of its smooth tuning in a fairly wide range. High-power single-pulse ELs excited by electron beams are used in installations for studying laser heating of targets for the purpose of carrying out thermonuclear reactions (for example, a KrF laser with HM, output energy per pulse up to 100 kJ, pulse duration ~ 1 nsec). Lasers with a high pulse repetition rate, excited by a pulsed gas discharge, are used in technol. purposes in the processing of microelectronic products, in medicine, in experiments on laser isotope separation, in probing the atmosphere in order to control its pollution, in photochemistry and in experiments. physics as an intensive source of monochromatic. UV or visible radiation.

Lit.: Excimer Lasers, ed. Ch. Rhodes, trans. from English, M., 1981; Yeletsky A. V.. Smirnov B. M., Physical processes in gas lasers, M.. 1985. A. V. Yeletsky.

(laser vision correction) and semiconductor manufacturing.

Laser radiation of an excimer molecule occurs due to the fact that it has an "attractive" (associative) excited state and a "repulsive" (non-associative) ground state - that is, there are no molecules in the ground state. This is because noble gases such as xenon or krypton are highly inert and do not normally form chemical compounds. In an excited state (caused by an electrical discharge), they can form molecules with each other (dimers) or with halogens such as fluorine or chlorine. Therefore, the appearance of molecules in an excited bound state automatically creates a population inversion between two energy levels. Such a molecule, which is in an excited state, can give up its energy in the form of spontaneous or stimulated emission, as a result of which the molecule goes into the ground state, and then very quickly (within picoseconds) decays into its constituent atoms.

Even though the term dimer refers only to the joining of identical atoms, and most excimer lasers use mixtures of noble gases with halogens, the name has stuck and is used for all lasers of similar design.

The wavelength of an excimer laser depends on the composition of the gas used, and usually lies in the ultraviolet region:

Excimer lasers usually operate in a pulsed mode with a pulse repetition rate from 1 Hz to several hundred Hz, in some models the frequency can reach 2 kHz; it is also possible to generate single pulses. Radiation pulses usually have a duration of 10 to 30 ns and an energy of a few to hundreds of mJ. The powerful ultraviolet radiation of such lasers allows them to be widely used in surgery (especially in the eye), in photolithography processes in semiconductor production, in the micromachining of materials, in the production of LCD panels, and also in dermatology. Today, these devices are quite bulky, which is a disadvantage in a wide medical application (see LASIK), but their size is constantly decreasing due to modern developments.

Write a review on the article "Excimer laser"

An excerpt characterizing the Excimer laser

Balashev respectfully allowed himself to disagree with the opinion of the French emperor.
“Every country has its own customs,” he said.
“But nowhere else in Europe is there anything like it,” said Napoleon.
“I apologize to Your Majesty,” said Balashev, “besides Russia, there is also Spain, where there are also many churches and monasteries.
This answer by Balashev, hinting at the recent defeat of the French in Spain, was later highly appreciated, according to Balashev's stories, at the court of Emperor Alexander and very little appreciated now, at Napoleon's dinner, and passed unnoticed.
It was clear from the indifferent and perplexed faces of the gentlemen of the marshals that they were perplexed, what was the witticism, which was hinted at by Balashev's intonation. “If she was, then we did not understand her or she is not witty at all,” said the facial expressions of the marshals. This answer was so little appreciated that Napoleon did not even notice it resolutely and naively asked Balashev about which cities there was a direct road to Moscow from here. Balashev, who was on his guard all the time of dinner, answered that comme tout chemin mene a Rome, tout chemin mene a Moscou, [as every road, according to the proverb, leads to Rome, so all roads lead to Moscow,] that there are many roads, and that among these different paths is the road to Poltava, which was chosen by Charles XII, said Balashev, involuntarily flushing with pleasure at the success of this answer. Before Balashev had time to say the last words: "Poltawa", Caulaincourt was already talking about the inconvenience of the road from Petersburg to Moscow and about his Petersburg memories.
After dinner we went to drink coffee in Napoleon's study, which four days earlier had been the study of Emperor Alexander. Napoleon sat down, touching the coffee in a Sevres cup, and pointed to a chair meanly to Balashev.
There is a certain post-dinner mood in a person, which, stronger than any reasonable reasons, makes a person be pleased with himself and consider everyone his friends. Napoleon was in this location. It seemed to him that he was surrounded by people who adored him. He was convinced that Balashev, after his dinner, was his friend and admirer. Napoleon turned to him with a pleasant and slightly mocking smile.
- This is the same room, as I was told, in which Emperor Alexander lived. Strange, isn't it, General? - he said, obviously not doubting that this appeal could not but be pleasant to his interlocutor, since it proved the superiority of him, Napoleon, over Alexander.
Balashev could not answer this and silently bowed his head.
“Yes, in this room, four days ago, Winzingerode and Stein conferred,” Napoleon continued with the same mocking, confident smile. “What I cannot understand,” he said, “is that Emperor Alexander brought all my personal enemies closer to him. I do not understand this. Did he think that I could do the same? - he asked Balashev with a question, and, obviously, this memory pushed him back into that trail of morning anger, which was still fresh in him.
“And let him know that I will do it,” said Napoleon, standing up and pushing his cup away with his hand. - I will drive out of Germany all his relatives, Wirtemberg, Baden, Weimar ... yes, I will drive them out. Let him prepare a refuge for them in Russia!
Balashev bowed his head, showing with his appearance that he would like to take his leave and is listening only because he cannot but listen to what he is told. Napoleon did not notice this expression; he addressed Balashev not as an ambassador of his enemy, but as a man who was now completely devoted to him and should rejoice at the humiliation of his former master.

EXCIMER LASER

- gas laser, operating on electronic transitions of excimer molecules (molecules that exist only in electronically excited states). Potential dependence. the interaction energy of excimer atoms, which is in the ground electronic state, on the internuclear distance is a monotonically decreasing function, which corresponds to the repulsion of nuclei. For the excited electronic , which is the top level of the laser transition, such a dependence has a minimum, which determines the possibility of the existence of the excimer itself (Fig.). The lifetime of an excited excimer molecule is limited

Dependence of the energy of an escimer molecule on distance R between its constituent atoms X and Y; the upper curve is for the upper laser level, the lower curve is for the lower laser level. The values correspond to the center of the active medium amplification line, its red and purple borders. time of its radiation. decay. Because the lower the state of the laser transition in E. l. is emptied as a result of the expansion of the atoms of the excimer molecule, characteristic of which (10 -13 - 10 -12 s) is much less than the radiation time. empty top, the state of the laser transition, containing excimer molecules, is active medium with amplification at transitions between the excited bound and ground expansion terms of the excimer molecule.

The basis of the active medium E. l. usually make up diatomic excimer molecules - short-lived compounds of atoms of inert gases with each other, with halogens or with oxygen. Radiation length E. l. lies in the visible or near UV region of the spectrum. The width of the amplification line of the laser transition E. l. is anomalously large, which is associated with the expansion nature of the lower transition term. The characteristic values of the parameters of laser transitions for the most common E. l. presented in the table.

Parameters of excimer lasers

At such high pressures, the most eff. the method of introducing pump energy into the active medium of the laser is associated with the transmission of a beam of fast electrons through the gas, which lose energy predominantly. to the ionization of gas atoms. Conversion of Atomic Ions to Molecular Ions and Subsequent Dissociation of Molecular Ions accompanied by the formation of excited atoms of an inert gas, provide the possibility of eff. conversion of the energy of a beam of fast electrons into the energy of excimer molecules Lasers based on inert gas dimers are characterized by ~1%. Main The disadvantage of lasers of this type is the extremely high value of beats. threshold energy input, which is associated with the short wavelength of the laser transition and, hence, the width of the gain line. This imposes high requirements on the characteristics of the electron beam used as a laser pump source and limits the values of the output energy of laser radiation to fractions of J (per pulse) at a pulse repetition rate of not more than a few. Hz. A further increase in the output characteristics of inert gas dimer lasers depends on the development of the technology of electron accelerators with an electron beam pulse duration on the order of tens of nsec and a beam energy of ~kJ.

Significantly higher output characteristics are distinguished by E. l. on monohalides of inert gases RX*, where X is a halogen. Molecules of this type are effectively formed in paired collisions, for example, or

These processes proceed with sufficient intensity already at pressures of the order of atmospheric pressure, so the problem of introducing energy into the active medium of such lasers turns out to be technically much less complicated than in the case of lasers based on inert gas dimers. Active medium E. l. on monohalides of inert gases consists of one or several. inert gases at a pressure of the order of atmospheric and a certain number (~ 10 -2 atm) of halogen-containing molecules. To excite the laser, either a beam of fast electrons or a pulsed electric beam is used. discharge. When using a beam of fast electrons, the output laser radiation reaches values of ~ 10 3 J at an efficiency of several times. percent and a pulse repetition rate well below 1 Hz. In case of using electric discharge, the output energy of laser radiation per pulse does not exceed a fraction of J, which is associated with the difficulty of forming a discharge that is uniform in volume in, therefore, volume at atm. pressure over time ~ 10 ns. However, when using electric the discharge achieves a high pulse repetition rate (up to several kHz), which opens up the possibility of a wide practical. use of this type of laser. Naib. widespread among E. l. obtained on XeCl, which is due to the relative ease of implementation of work in the high pulse repetition rate mode. cp. The output of this laser reaches the level of 1 kW.

Along with high energy characteristics An important attractive feature of E. l. is an extremely high value of the active transition amplification linewidth (Table). This opens up the possibility of creating high-power lasers in the UV and visible ranges with smooth wavelength tuning in a fairly wide spectral region. This problem is solved with the help of an injection laser excitation circuit, which includes a low-power generator of laser radiation with a wavelength tunable within the width of the amplification line of the EL active medium, and a broadband amplifier. This scheme makes it possible to obtain a laser with a line width of ~ 10 -3 HM, tunable in wavelength in a range of width ~ 10 HM or more.

E. l. are widely used due to their high energy. characteristics, short wavelength and the possibility of its smooth tuning in a fairly wide range. High-power single-pulse ELs excited by electron beams are used in installations for studying laser heating of targets for the purpose of carrying out thermonuclear reactions (for example, a KrF laser with an HM, output energy per pulse up to 100 kJ, and pulse duration ~ 1 nsec). Lasers with a high pulse repetition rate, excited by a pulsed gas discharge, are used in technol. purposes in the processing of microelectronic products, in medicine, in experiments on laser isotope separation, in probing the atmosphere in order to control its pollution, in photochemistry and in experiments. physics as an intensive source of monochromatic. UV or visible radiation.

Lit.: Excimer Lasers, ed. Ch. Rhodes, trans. from English, M., 1981; Yeletsky A. V.. Smirnov B. M., Physical processes in gas lasers, M.. 1985. A. V. Yeletsky.

Physical encyclopedia. In 5 volumes. - M.: Soviet Encyclopedia. Editor-in-Chief A. M. Prokhorov. 1988 .

See what the "EXCIMER LASER" is in other dictionaries:

The excimer laser is a type of ultraviolet gas laser widely used in eye surgery (laser vision correction) and semiconductor manufacturing. The term excimer (English excited dimer) denotes an excited dimer and ... ... Wikipedia

excimer laser- A gas laser in which a laser active medium in the form of an unstable compound of ions is created in a gas discharge under electrical pumping. [GOST 15093 90] Topics laser equipment EN excimer laser ... Technical Translator's Handbook

excimer laser- eksimerinis lazeris statusas T sritis radioelektronika atitikmenys: engl. excimer laser vok. Excimer Laser, m rus. excimer laser, m pranc. laser à excimères, m … Radioelectronics terminų žodynas

This term has other meanings, see Laser (meanings). Laser (NASA laboratory) ... Wikipedia

A laser used to remove very thin layers of tissue from the surface of the cornea. This operation can be performed to change the curvature of the surface of the cornea, for example, in the treatment of myopia (photorefractive keratectomy ... ... medical terms

- (abbreviation for Light Amplification by Stimulated Emission of Radiation) a device that allows you to get a very thin beam of light with a high concentration of energy in it. In surgical practice, the laser is used to perform operations, ... ... medical terms

LASER- (laser) (abbreviation for Light Amplification by Stimulated Emission of Radiation) a device that allows you to get a very thin beam of light with a high concentration of energy in it. In surgical practice, the laser is used to perform operations, ... ... Explanatory Dictionary of Medicine

EXCIMER LASER- (excimer laser) a laser used to remove very thin layers of tissue from the surface of the cornea of the eye. This operation can be performed to change the curvature of the surface of the cornea, for example, in the treatment of myopia (photorefractive ... ... Explanatory Dictionary of Medicine

Photolithography line for the production of silicon wafers Photolithography is a method of obtaining a pattern on a thin film of material, widely used in microelectronics and printing. One of ... Wikipedia

Books

High-voltage pulse generators based on composite solid-state switches, Khomich Vladislav Yurievich, Moshkunov Sergey Igorevich. The monograph is devoted to the development and creation of high-voltage semiconductor-based pulse generators. The basic principles of building composite high-voltage…

Excimer laser unit WaveLight EX500

WaveLight EX500 is the latest generation excimer laser unit, the use of the unique advantages of which allows the patient to achieve the best visual acuity in the most comfortable and safe way.

The operating pulse frequency is 500 Hz, which makes WaveLight EX500 one of the fastest excimer laser systems in the world. Due to the high speed of the laser, the cornea is not exposed to excessive thermal effects, which prevents its dehydration during the procedure - accordingly, the recovery period after laser correction is reduced and proceeds as comfortably as possible.

The new excimer laser unit is fully integrated with the diagnostic complex - a single server for diagnostic equipment and a surgical laser allows you to fully automate data transfer, which minimizes the human factor. The built-in pachymeter provides additional control of the depth of laser exposure, allowing you to measure the thickness of the cornea online, at all stages of surgery.

The infrared tracking system, which monitors the center of the pupil and is synchronized with the laser source itself, allows you to accurately determine the area of impact of the laser. The reaction time of the eye tracking system is less than 3 milliseconds. The frequency of the eye tracking system is 1050Hz. Controlling the position of the eye in the center of the pupil, the edge of the cornea, the iris allows you to track the slightest eye movements in such a way that the accuracy of the correction is not affected.

Thanks to the use of optimized and controlled wavefront technologies, the risk of spherical aberrations is prevented, and patients have virtually no problems associated with impaired twilight and night vision.

Limits of application of the WaveLight EX500 excimer laser system:

myopia from -0.25 to -14.0 D;
myopic astigmatism from -0.25 to -6.0 D;
hyperopia from +0.25 to +6.0 D;
hyperopic astigmatism from +0.25 to +6.0 D.

Laser VISX Star S4 IR

The VISXStarS4 IR laser differs significantly from other models - it allows excimer laser correction for patients with complicated forms of myopia, hyperopia and aberrations (distortions) of higher orders.

The new integrated approach implemented in the VISX Star S4 IR device allows guaranteeing the smoothest corneal surface formed during laser correction, tracking possible minor movements of the patient's eye during the operation, and maximally compensating for the most complex distortions of all optical structures of the eye. Such characteristics of the excimer laser significantly reduce the likelihood of postoperative complications, significantly reduce the rehabilitation period, and guarantee the highest results.

Application limits:

Myopia (myopia) up to -16 D;
Farsightedness (hypermetropia) up to +6 D;
Complex astigmatism up to 6 D.

Femtosecond lasers

Femtosecond laser FS200 WaveLight

The FS200 WaveLight femtosecond laser has the fastest corneal flap formation in just 6 seconds, while other laser models form a standard flap in 20 seconds. During excimer laser correction, the FS200 WaveLight femtosecond laser creates a corneal flap by applying very fast pulses of laser light.

The femtosecond laser uses a beam of infrared light to accurately separate tissue at a given depth through a process called phototearing. A pulse of laser energy is focused at a precise location within the cornea, thousands of laser pulses are placed side by side to create an access plane. Due to the application of multiple laser pulses according to a certain algorithm and at a certain depth in the cornea, it is possible to cut out a corneal flap of any shape and at any depth. That is, the unique characteristics of the femtosecond laser enable the ophthalmic surgeon to form a corneal flap, fully controlling its diameter, thickness, centering and morphology with minimal disruption of the architecture.

Most often, a femtosecond laser is used during excimer laser correction using the FemtoLasik method, which differs from other methods in that the corneal flap is formed using a laser beam, and not a mechanical microkeratome. The absence of mechanical action increases the safety of laser correction and several times reduces the risk of acquired postoperative corneal astigmatism, and also allows laser correction to be performed in patients with thin corneas.

The FS200 WaveLight femtosecond laser is integrated into a single system with , and therefore the time for the excimer laser correction procedure using these two laser units is minimal. Due to its unique properties for creating an individual corneal flap, the femtosecond laser is also successfully used in the course of keratoplasty in the formation of a corneal tunnel for subsequent implantation of the intrastromal ring.

Femtosecond laser IntraLase FS60

The IntraLase FS60 femtosecond laser has a high frequency and short pulse duration. The duration of one pulse is measured in femtoseconds (one trillionth of a second, 10-15 s), which allows you to separate the layers of the cornea at the molecular level without heat generation and mechanical impact on the surrounding eye tissues. The process of forming a flap using a femtosecond laser FS60 for laser vision correction occurs in a few seconds, absolutely contactless (without corneal incision).

The IntraLase FS60 femtosecond laser is part of the complete line of iLasik system equipment. It works in conjunction with the VISX Star S4 IR excimer laser and the WaveScan aberrometer. This complex makes it possible to carry out laser vision correction, taking into account the slightest features of the patient's visual system.

Microkeratomas

The result of laser correction depends on many parameters. This is the experience of a specialist, and the method of treatment used, and the laser used during the correction. But no less significant in the treatment process is such a device as a microkeratome. Microkeratome is required for excimer laser correction according to the LASIK method. The peculiarity of microkeratoms used in Excimer clinics is the highest safety. They can work offline, regardless of the power supply. During LASIK treatment, not the outer layers of the cornea are affected, but the inner ones. In order to separate the upper layers of the cornea, a microkeratome is needed. The Excimer clinic uses microkeratoms of the world-famous Moria company. She was one of the first to produce not manual, but automatic models, which made it possible to minimize risks during excimer laser correction and significantly improve its quality.

Moria Evolution 3

This type of microkeratome makes it possible to carry out the preparatory stage before excimer laser vision correction (namely, the formation of a flap) in the least painful way for the patient and to reduce the state of discomfort to a minimum. The device is equipped with reusable heads, fixing vacuum rings, as well as directly with an automatic rotary type keratome. The design of the rings and heads of the microkeratome allows you to flexibly adjust the equipment to the individual characteristics of the patient's eye, which leads to more accurate and guaranteed results.