Let's talk today about what a femtosecond laser is. What are the main principles of its work and how does it help correct vision?
Bohr's Theory
When at the beginning of the nineteenth century science reached such a level that it was able to look into the structure of the atom, a new direction arose - quantum physics. The first task was to determine how and why small electrons do not fall on the heavy nucleus of an atom. A previous theory based on Maxwell's equations stated that any moving charge emits a field and therefore loses momentum. Thus, an electron that orbits around the nucleus must continuously radiate and eventually fall onto the nucleus. Bohr expressed the idea that electrons in an atom can only be at certain distances from the center, and the transition from one level to another is accompanied by either the emission or absorption of energy. This theory was subsequently explained within the framework of quantum physics. The presence of stationary electronic levels opened the way for such an invention as a laser (including a femtosecond one).
Theoretical foundations of the laser
Once scientists realizedstructure of the atom, they wanted to learn how to control the state of the electron. Under normal conditions, an electron, which for some reason is at a high level of an atom, tends to fill the lower levels, if they are free. During the transition, energy is emitted in the form of a quantum of light or a photon. But the transition between any two levels generates different light quanta. But if many electrons pass simultaneously from a higher level to a lower level, then a stream of many identical photons will appear. The applications of this thread are endless. For example, a femtosecond laser removes cataracts. In a ruby doped with yttrium, a level with the so-called inverse population was found: when electrons more readily gather at a high level, and then all together move to a lower level. The main components of the laser are as follows:
- working body (substance in which there is a level with inverse population);
- pump (a source that "induces" electrons to accumulate at the inverse level);
- resonator in the form of two parallel mirrors (they concentrate only those photons that are generated in one direction, and all the rest are scattered).
The output pulse can be continuous or discrete. The femtosecond laser, for example, belongs to the second type.
Micro, nano, femto
All these prefixes denote part of a whole. A milli is one thousandth of something, such as a metre. That is, a millimeter is 10-3 meters. The prefix femto- means that something weighs orstretches 10-15 times less than a certain unit. Accordingly, the femtosecond laser has a very short pulse. And every second fits 1015 pulses. Why do we need such an unimaginably small value? The fact is that the laser power depends on how long electrons accumulate at the inverse level. With continuous generation, the power of lasers cannot be high. But the shorter each pulse, the higher the output. Many processes take much longer, and such a short impulse is not noticeable for the final goal. The receiving system appears to be a continuous laser. At the same time, the coherence and power of the output beam is much higher.
Cataract
Cataract is a clouding of the lens. A person who develops such a visual defect may not be aware of it: with the development of a cataract at the edge of the pupil, vision is not impaired. But if clouding occurs in the center of the lens, then it is impossible not to notice the weakening of vision. There are four main reasons for this change in the eye:
- harmful radiation in high doses;
- trauma to the head or directly to the eye;
- diabetes mellitus;
- strong stress.
There is only one physical reason - the protein contained in the lens of the eye begins to degrade, break down. This process is called protein denaturation. In the case of the lens, the destruction is irreversible. Previously, old people with white eyes were completely dependent on their relatives, as they were actually blind. However, this disease is now successfullybeing treated.
Cataract treatment with surgery
Traditionally, treatment means such an intervention in the human body that does not violate its integrity: a sore throat is treated with pills and hot tea, a cut finger with ointments and a bandage.
But in this case, the treatment is radical - surgery. Usually, this word means wounds, stitches that heal for a long time, pain and the loss of a normal lifestyle. In the case of a cataract, there is no need to be afraid of the operation, because the incision is usually very small, 2-3 mm, no blood vessels are cut, the anesthesia is local.
Steps of the operation:
- The eyeball is anesthetized with special drops.
- The iris of the eye is incised (the cut is no more than 3 mm long).
- A special device is inserted into the lens.
- The device turns the old lens into an emulsion.
- The emulsion is sucked off.
- Introducing a new artificial soft lens.
- The device is removed from the eye.
The procedure lasts no more than 15 minutes, after which the person can already go home.
It is at the stage of the transformation of the old lens into an emulsion that a femtosecond laser is used. Ophthalmology also knows another example of the use of lasers - the correction of myopia and astigmatism. But that's a different story.
Advantages of lasers in cataract treatment
Immediately, we will name one significant drawback - this method is quite expensive. However, in all other respects it is better than before.methods. According to the reviews, the tissue surrounding the lens is less damaged, the transformation into an emulsion takes place faster, the size of the resulting particles is smaller if a femtosecond laser is used in the operation. Feedback on such an operation is extremely positive from both patients and doctors.
We have already mentioned that with the help of lasers myopia is also corrected. However, until recently, different equipment was used for this operation and cataract treatment. The main thing for the patient is the quality of the operation, but the clinic that provides such services would like to spend less money on devices. In this case, the Victus femtosecond laser will help out: it can be used to perform three different operations. In this case, you just need to change the settings.
