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Since the birth of laser, scientists have tried to apply it to medical treatment. In recent years, due to the rapid development of laser technology, European and American countries have made a series of breakthroughs in the field of laser medicine and cosmetology. Laser products are growing well in markets that are not affected by the recession, such as aerospace, energy, transportation, medical equipment and metal products. A new round of scientific and technological revolution is constantly giving birth to new formats, intelligent manufacturing, laser 3D printing and other new application areas continue to expand and extend; cross-border integration of technology and industry gives birth to a new business model.
The wavelength of femtosecond laser varies from hundreds to thousands of nanometers (nanometers), while the wavelength of femtosecond laser used in myopia surgery is 1030-1064 nanometers. It is an invisible near-infrared laser. The laser of this kind of wavelength can accurately focus on the bright or semi-bright biological arrangement (cornea), and the concentration intensity is high. The photoblasting effect on the cornea arrangement can separate the cornea arrangement from a lubrication. The plane. The corneal arrangement of femtosecond laser before the focusing point will not absorb the energy of femtosecond laser, so the corneal part passing before the focusing point will not be harmed by the light energy of femtosecond laser when the femtosecond laser breaks out in one of the focusing layers of cornea.
The pulse width is generally indicated by milliseconds, nanoseconds, femtoseconds, picoseconds, and the like. The smaller the value of the pulse width, the shorter the time at which the laser energy continues to effect the corneal arrangement, and the smaller the effect on the corneal collagen, the more subtle the arrangement is. However, there is no direct influence on the number of corneal interlayer bubbles (OBL). The femtosecond laser has a very short pulse width, and the femtosecond laser that shortens the "pulse continuation time" can significantly reduce the threshold energy that causes the laser cracking effect, and reduces related side effects, especially thermal effects. In general, pulse widths greater than 1 μs are often accompanied by thermal effects, and pulse width thermal effects less than 1 μs are small and can be ignored, known as the 1 μs law. The pulse widths of nanoseconds, picoseconds, and femtosecond lasers are all less than 1 μs, especially femtoseconds, with no thermal effects.
It refers to the scale of laser illumination in normal aggregation. Different laser systems can form different spot shapes and sizes. For example, the spot of a brand femtosecond laser is less than 3μm (micron), and the spot of another brand femtosecond laser is 2μm. (micron), the larger the spot size of the laser, the simpler it is to create large bubbles between the corneal layers. The larger the bubble, the harder it is to uncover the corneal flap, the longer the bubble absorption time, and the longer the patient will wait during surgery. In addition, the same femtosecond laser instrument can have different size and shape of the spot due to the different curvature of the spot when the size of the emitted spot is constant.
The pulse repetition rate, also called the pulse frequency, is the frequency at which the laser pulse is repeatedly transmitted, and is the reciprocal of the pulse continuation time (pulse width), that is, the number of pulses per second. The pulse repetition rate of different brands of femtosecond lasers is quite different, which is determined by the characteristics of the instruments. It has nothing to do with the quality of the equipment, and it does not make much difference between the timing and effect of the flap. A brand with a high pulse repetition rate does not mean that the brand produces a corneal flap with a lower pulse repetition rate. The pulse repetition rate is directly related to the laser spot size. The small spot femtosecond laser has a high pulse repetition rate and a large spot device. The pulse repetition rate is slightly lower. This is because it is necessary to improve the frequency of laser emission in order to complete the corneal flap with the same size and large size in order to complete the small spot device with the large spot device.
Although different femtosecond laser systems have different pulse frequencies, pulse duration, pulse energy, focus density, point distance, line distance, corneal appearance and contact mode with negative pressure touch lens, the basic principle is similar. In order to achieve better results and reduce the side effects of corneal arrangement, the relevant laser parameters and surgical techniques need to be carefully carried out. Analysis, and give the parameters combination optimization and necessary adjustment. For example, the relationship between pulse width and laser energy settings. Generally speaking, the longer the laser pulse continues, the greater the energy required for light cutting, but the greater the pulse energy, the greater the side effects may be. If the pulse continues for a long time, more rated heat, oscillation and sound waves will occur, which can bake, blend or change the arrangement around the laser scanning area. The ablation effect of excimer laser is arranged on the surface, the rated heat and gasified substances are simply lost in the air, so almost all excimer laser systems have a suction tube device to absorb the substances dispersed in the air. Similarly, excimer lasers sometimes have thermal effects on the arrangement. Only excimer lasers of different brands produce heat. The effect is different, not like the so-called "cold laser" advocated by some manufacturers and medical institutions.
Femtosecond lasers, on the other hand, have a very short duration of pulse continuation. Before the thermal and oscillatory waves are dispersed around them, the energy and the matter generated by the laser are lost. When the laser pulse continues to shorten, higher power density can be obtained per unit time, and the pulse energy required to produce the optical cutting effect decreases significantly. Reducing the energy of femtosecond laser pulse can reduce the harm of laser to the surrounding arrangement as much as possible, which is negligible. This is also an important reason why femtosecond laser technology is widely used in other ophthalmology specialties, especially cataract surgery. It is also the main factor that all femtosecond laser Smile surgery is called the trend of corneal refractive surgery in the future. Laser surgery is effective for myopia, but it does not guarantee 100% recurrence. Here is also a reminder that after laser surgery, we should cherish our eyesight and protect our eyes. Before doing this, we should also think clearly. After all, surgery is risky. Prevention is always more effective than treatment.