In this article, we 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 procedures 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 light beam. Laser devices open up incredible opportunities for energy transfer at different distances with high speed. Ordinary light, which is capable of being perceived by human vision, is small beams of light that propagate in different directions. If these beams are concentrated using a lens or mirror, a large beam of light particles will be obtained, but even it cannot be compared with a laser beam that 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 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 introduced in 1971 by scientists V. A. Danilichev, N. Basov, and Yu. M. Popov in Moscow. A xenon dimer was used as the working fluid of such a laser, 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. Sirles.
People often ask why an excimer laser is used to correct vision.
Its uniqueness
It was found that the excimer molecule produces laser radiation due to the fact that it is in an excited “attracting” 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 electric discharge leads them to an excited state, as a result of which they can form molecules either between 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 off 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 identical atoms are joined together, however, in most modern excimer lasers, compounds of noble gases and halogens are used. Nevertheless, these compounds are also called dimers, which are used for all lasers of a similar design. How does an excimer laser work? We will consider this now.
Excimer laser principle
This laser is the main protagonist of PRK and LASIK. Its working body is an inert and halogen gas. When a high voltage penetrates into the mixture of these gases, one halogen atom and one inert gas atom combine to form a diatomic molecule. It is in an extremely 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 action of an excimer laser has found wide application in medicine, since ultraviolet radiation acts on organic tissues, for example, on the cornea, so that the bonds between the molecules are disconnected, leading to the transfer of tissues from solid to gaseous state. This process is called "photoablation."
Wave range
All existing models of this type operate in the same wavelength range and differ solely in the width of the light beam, as well as in the composition of the working fluid. An excimer laser for vision correction is most often used. But there are other areas of its use.
The former had a diameter of the light beam, which was equal to the diameter of the surface on which the evaporation was carried out. A wide range of the beam and its heterogeneity caused the same heterogeneity 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. The creation of an excimer laser corrected this situation. MNTK “Eye Microsurgery” has been using it for a very long time.
The new generation lasers went through a long modernization process, 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 lasers are used by doctors.
Medical use
In a transverse 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 flat and clear surface of the cornea is observed. An excimer laser in ophthalmology is indispensable.
The surgeon performing the surgical intervention determines in advance what portion of energy that will be supplied to the cornea, as well as to what depth the excimer laser will produce. From here, the specialist can plan the progress 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 that is 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 is applied to it, smoothes the surface of the cornea, removing the upper layers and, thus, eliminating all defects on it. In this case, normal conditions appear for the eye to obtain the correct images, creating the correctness of light refraction. People who underwent such a procedure see how everyone who has initially good vision.
The corneal reprofiling procedure does not cause high temperatures to appear on its surface, which can be detrimental to living tissues. And, according to most people, the so-called burning of the upper layers of the cornea does not occur.
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 abnormalities. These devices are so high-precision that they provide "photochemical ablation" of the upper layers.
For example, if this process is carried out in the central zone of the cornea, then its shape becomes almost flat, and this helps to correct myopia. If in the process of vision correction the layers of the cornea in the periphery zone evaporate, 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 microsurgery of the eye, guarantee a high quality surface that undergoes photoablation.
Features of use in medicine
Excimer lasers in the form they have today appeared recently, but now they are helping people around 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 effectiveness.
Eye diseases that are treated by application
The field of ophthalmic surgery that deals with the removal of these abnormalities of the human eye is called refractive surgery, and such disorders are called anomalies of ametropia and refraction.
According to experts, two types of refraction are distinguished:
- emmetropia, which characterizes normal vision;
- ametropia, consisting in abnormal vision.
Ametropia, in turn, includes several subspecies:
- myopia (myopia);
- astigmatism - the eye receives a distorted image when the cornea has an irregular curvature, and the flow of light rays becomes uneven in different parts of its surface;
- hyperopia (hyperopia).
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 optics system of the eye consists of three main elements - the cornea, the lens, which are light-refracting parts, and the retina, which is the light-reflecting part. In order for the resulting image to become clear and sharp, the retina is in the focus of the ball. However, if it is in front of the focus, and this 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 to 16-20 years, it changes due to the growth and increase in size of the eyeball, as well as under the influence of some factors that can lead to the formation of certain anomalies . Thus, patients of the surgeon involved in eye refraction, most often become adults.
Contraindications to the procedure for correcting vision with an excimer beam
Excimer laser vision correction is not shown to all people suffering from visual impairment. The ban on the use of this procedure are:
- ophthalmic diseases (glaucoma, cataract, retinal deformation);
- diseases that interfere with the normal healing of wounds (arthritis, diabetes mellitus, autoimmune diseases, etc.);
- heart and vascular system diseases;
- monocularity;
- retinal detachment;
- age presbyopsy;
- pregnancy and breastfeeding;
- children under 18 years old;
- accommodation spasm;
- progressive changes in eye refraction;
- inflammatory processes in the body, including those directly affecting the eyes.
Possible complication after application
All existing excimer laser treatment methods today are highly safe and particularly effective. Nevertheless, there are a number of complications that may arise after surgery using similar 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 develops redness and pain in the eye. This complication can occur in cases where nerve endings that are responsible for the production of tears were damaged in the process of vision correction.
- A variety of visual disturbances, for example, double vision or decreased vision in the dark, impaired color perception or the appearance of a light halo.
- Weakening or softening of the cornea, which can occur both a few months after surgery, and 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;
- painkiller;
- immunomodulatory.
That is, there is a certain biostimulating mechanism of action of laser radiation with low power.
Successfully undergoing vitiligo excimer laser treatment. The age spots on the skin smooth out very quickly.