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. Laser operations 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?
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 beam of light that spreads 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 does notcan 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 the 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:
- solid;
- dye lasers;
- gas;
- excimer;
- semiconductor;
- metal vapor lasers;
- chemical;
- fiber;
- free electron lasers.
Origin
This variety is an ultraviolet gas laser, which is widely used in the field of eye surgery. With 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 askwhy an excimer laser is used for vision correction.
His uniqueness
It was found that the excimer molecule produces laser radiation 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, but most modern excimer lasers use compounds of noble gases and halogens. Nevertheless, these compounds, which are used for all lasers of this design, are also called dimers. How does an excimer laser work? We will now consider this.
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, decays into atoms, which leads to the appearance of a light wave in the UV range.
This principle of the excimer laser has been widely used 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 transition 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 uses as well.
The first had the diameter of the light beam, which was equal to the diameter of the surface on which the evaporation was carried out. 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.
Lasers of the new generation underwent a long process of modernization, during which the diameter of the light beam was reduced, and a special rotational-scanning system for delivering laser radiation to the eye was also created. Consider how excimer lasersused by doctors.
Medical applications
In cross section, such a laser beam looks like a spot moving in a circle, removing the upper layers of the cornea, and also 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 applied 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 had this procedure see like everyone who has good vision from the start.
The corneal reshaping procedure does not cause high temperatures on its surface, which can be detrimental toliving 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 the perfect 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 high quality of the surface that is subjected to photoablation.
Features of use in medicine
Excimer lasers in the form they have today appeared only recently, but now they help people all over the world to get rid of such vision problems as nearsightedness, farsightedness, 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.
Eye diseases that are treated byapplications
The field of ophthalmosurgery 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:
- emmetropia, which characterizes normal vision;
- ametropia, consisting in abnormal vision.
Ametropia, in turn, includes several subspecies:
- myopia (myopia);
- astigmatism - getting 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;
- hyperopia (farsightedness).
Astigmatism is of two types - hyperopic, which is close to farsightedness, myopic, similar to myopia and mixed.
In order to correctly represent the essence of refractive manipulations, it is necessary to know minimally the anatomy of the human eye. 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.
HumanThe optics of the eye can change throughout life, in particular, from the moment of birth until the age of 16-20, 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 a refractive eye surgeon are most often 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:
- ophthalmic diseases (glaucoma, cataract, retinal deformity);
- diseases that interfere with normal wound healing (arthritis, diabetes, autoimmune diseases, etc.);
- diseases of the heart and vascular system;
- monocular;
- retinal detachment;
- age presbyopsia;
- pregnancy and breastfeeding;
- Children under 18;
- accommodation spasm;
- progressive changes in the refraction of the eye;
- inflammatory processes in the body, including those directly related to the eyes.
Possible complications after application
All existing excimer laser treatment methods today are highly safe and especially effective. However, there are a number of complications that can occur after surgery usingsimilar methods. 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 if the nerve endings that are responsible for the production of tears were damaged during vision correction.
- Various visual disturbances, such as double vision or decreased vision in the dark, impaired perception of colors or the appearance of a halo of light.
- Weakening or softening of the cornea, which may occur months after surgery or years.
Excimer laser in dermatology
The effect of low-frequency laser on the skin is extremely positive. This is due to the following effects:
- anti-inflammatory;
- antioxidant;
- painkiller;
- immunomodulating.
That is, there is a certain biostimulating mechanism of action of laser radiation with low power.
Vitiligo undergoes successful excimer laser treatment. Age spots on the skin are smoothed out very quickly.
