The principle of PRK- excimer laser keratectomy is to use excimer laser to cut the central front surface of cornea, that is, to remove the shallow matrix of anterior elastic layer and epithelial layer, so that the curvature of the front surface of cornea decreases, the radius of curvature increases, the refractive power decreases, and the focus moves back to the retina to correct myopia, which is like grinding a pair of myopia lenses on your own cornea. LASIK has been gradually replaced by LASIK because of postoperative pain, long-term medication and easy regression.
The principle of LASIK- excimer laser in situ keratomileusis is to make a lamellar corneal flap with pedicle on the corneal surface by using an automatic microscopic corneal lamellar system, turn the corneal flap over, cut the corneal stroma in multiple steps by using excimer laser computer control, and finally reset the corneal flap. This method preserves the integrity of corneal epithelium and anterior elastic layer, and uses 193 nm excimer laser to cut corneal stroma, thus avoiding the occurrence of haze after operation. This kind of surgical equipment is precise and expensive, which requires high surgical technology and sterile surgical environment and can only be performed in large hospitals with good conditions. At present, LASIK has become the most commonly used refractive surgery method, and it is widely used all over the world to take off glasses for many myopia and hyperopia patients. This technique is suitable for myopia patients within 1400 degrees.
PRK has been gradually replaced by LASIK because of postoperative pain, long-term medication and easy regression.
Among them, Torsion Lasik is abbreviated as TK, which is translated into excimer laser myopia surgery with iris recognition, rotational positioning and wavefront aberration guidance in Chinese, which is a leap in traditional laser myopia surgery. At present, there are only a handful of people who can perform this kind of operation in China.
LASEK- excimer laser keratomileusis is a new generation of excimer laser surgery. Different from LASIK, it uses a corneal epithelial trephine to cut the epithelial flap, with a thickness of 60-80 microns, a diameter of 8- 10 mm and a pedicle curvature of 30 degrees. After opening the epithelial flap, the corneal diopter was changed by in-situ grinding with excimer laser to correct myopia and astigmatism, and then the epithelial flap was reset. After operation, ultra-high patients can solve the problems of aberration and glare. Because the thickness of epithelial flap is 60-80 microns, the thickness problem is solved for patients with relatively thin cornea and high height, and the safety of such patients is also improved.
In this section, edit the biological characteristics of excimer laser. Any change in biological tissue caused by the interaction between laser and biological tissue is called the biological effect of laser.
What happens when excimer laser interacts with biological tissue is not thermal effect, but photochemical reaction. The so-called photochemical reaction means that when the tissue is irradiated by far ultraviolet light, it will break the bonds between molecules, directly separate the tissue into volatile fragments and dissipate them without a trace, but it has no effect on the surrounding tissues.
The light energy of excimer laser is almost completely absorbed by corneal epithelial cells, Bowman's membrane and matrix. Marshall used hydrogen fluoride excimer laser to photolyse animal cornea and examined its ultrastructure. It is found that the photolysis incision has clear boundary and no thermal damage around it.
193nm Ar-F excimer laser has many characteristics and is suitable for corneal refractive surgery. The energy of each pulse is as high as 6.4eV, which is far greater than the binding energy of carbon and carbon bonds. Therefore, photons can break the binding bonds between molecules and separate tissues into volatile fragments. At this wavelength, the laser absorption range is extremely narrow, about 3.7-3.9μm, that is, the tissues beyond this range will not absorb the laser, and each laser beam can cut biological tissues with a thickness of 0.2-0.25 μ m. Because the whole laser pulse is only 10-20μ s, its thermal diffusion effect is very small, and only the surrounding tissues of 0.3-0.8μm will be damaged.
In addition, the penetration of electromagnetic waves into cornea decreases with the shortening of wavelength. Below 400 nm, the penetration decreases to zero. Therefore, far ultraviolet rays with the wavelength of 193nm will not penetrate the cornea. Therefore, it will not have any adverse side effects on the tissues inside the eyeball.
The ability of excimer laser to cut cornea has ultra-fine precision and ultra-fine damage degree. Long-term ultraviolet light with the wavelength of 193nm only produces little thermal effect, thus limiting the damage to surrounding tissues to a small range. In addition, a particularly smooth cutting plane is provided.
Edit the postoperative sequelae and precautions of this paragraph.
[1] Myopia surgery is mainly done on the cornea, and there are no blood vessels and nerves on the cornea, so you have no pain in the operation. In myopia surgery, the good cooperation of patients is an important prerequisite for the success of the operation. Therefore, in myopia surgery, patients should pay attention to the following points: 1, relax and don't be nervous.
2. Don't squint hard, don't move your eyes at will, and fix them according to the doctor's instructions.
3. At the critical moment of operation, follow the doctor's advice, don't talk and don't move.
During the operation, you must pay attention to the flashing red or green staring light. Even if you can't see the staring light, don't move it. Move your eyes gently according to the doctor's instructions, but don't move your head.
5. On the operating table, don't touch the surgical disinfection area with your hands.
Sequela of operation
1. Undercorrection or overcorrection: It is the most common side effect, residual myopia after operation, or hyperopia caused by exceeding the expected correction degree. Depending on the situation, laser correction can be carried out again after the degree is stable.
2. photophobia: within 3 to 6 months after operation, the sensitivity to light increases, but it will gradually disappear after 6 months, and very few cases will last.
3. Glare or diplopia: It is more common in the early stage of surgery, especially when the pupil becomes larger at night, most of them will gradually disappear and a few will last.
4. Surgical complications: most of them are poor corneal flap cutting, such as incomplete or uneven cutting; As long as the corneal flap is reset, it can be restored, and it can be operated again after three months.
5. Poor epidermal healing: it is common in PRK and can be recovered by therapeutic contact lenses and artificial tears.
6. Corneal opacity: It only occurs after PRK, and it is positively correlated with personal physique and high degree of correction. It is most obvious at 65,438+0-3 months after PRK, which needs steroid eye drops to control, and then most of it will gradually fade away.
7. Corneal flap wrinkling or displacement: only seen in LASIK, it may be caused by trauma, which will cause irregular astigmatism and affect vision, and can be smoothed by surgery.
8. There are impurities or epidermal invasion under the corneal flap: the light one will not affect the vision, and the severe one must open the corneal flap and remove it.
9. Infection: The wound is unlikely to be infected with germs due to unclean operation or after operation. As long as it is found early, most of it can be controlled by drugs.
10. dry eye: after laser surgery, the secretion of tears will decrease, which may cause dry eye symptoms or aggravate the symptoms of people with dry eye. Artificial tears should be supplemented and can be improved in about 3-6 months.
1 1. Presbyopia: People who are close to or over 40 years old may have presbyopia. After myopia correction, you should wear glasses even if you are far away, but you should wear glasses when reading. Please discuss with your doctor the corrective method that suits you.
12. Surgery cannot guarantee that the vision will reach 1.0. In some cases, it may be necessary to have another operation or wear glasses to get the best vision.
Corneal injury caused by operation
Barris Sommertz of David Griffin School of Medicine at UCLA and Robert K. maloney of maloney School of Vision published an article in Ophthalmology, introducing their experience in treating "central corneal lesion" after laser surgery for myopia.
Some ophthalmologists pointed out that since 1998, cases of corneal diseases caused by laser surgery have appeared continuously. Professor Sommertz and maloney studied 14 similar cases involving 23 eyeballs. Eyeball vision improved after LASIK 19. However, four eyeballs had problems after operation. Central corneal opacity usually occurs 3-6 days after operation. The lesion is located in the center of cornea, which is the area with the strongest laser power in myopia laser surgery. The patient also developed "hyperopia", that is, focusing disorder. But after 2 ~ 18 months, the turbidity gradually disappeared.
It may be because of laser allergy: Dr. Sommertz and Dr. maloney both believe that "central corneal lesion" is not inflammation, and they warn that corticosteroids cannot be used for treatment, because long-term use may lead to cataract, glaucoma and even blindness.
In their case, seven patients underwent LASIK again after corneal opacity disappeared, and their vision was improved, and then there was no corneal opacity. Based on this, the two doctors speculated that the opacity after myopia laser surgery may be the reaction phenomenon of the patient's cornea after laser allergy, so "some external stimulation means are needed" to improve the symptoms.
Precautions before operation
1. Stop wearing contact lenses before examination. Soft lenses take at least 1-2 weeks, and hard lenses take at least 2-3 weeks. Stop wearing contact lenses as long as possible.
2. Practice watching nothing for more than 2 minutes at a time.
Please don't use any cosmetics and perfume for three days before the operation.
4. Arrange surgical escort for postoperative escort.
Possible problems after operation
1. Glare and night vision disorder: If the myopia degree is above 700- 1000 degrees, 80% people will have slight glare at night, and 25% people will have vision problems at night. This is mostly due to the fact that the operation area is close to the visual center during the operation.
2. Dissatisfied with the corrected vision: after operation, the degree of correction may be insufficient, worse than expected, or over-corrected, and hyperopia, that is, presbyopia, may be advanced.
3. Dry eye: The tear film nerve may be damaged during the operation, which will reduce the secretion of tears.
4. Pseudokeratoconus: an extreme problem after surgery. This is caused by cutting too deep, which will make your eyesight worse. Fortunately, the probability of occurrence is very low.
Matters needing attention after operation
Within 24 hours: it is better to sleep in supine position to avoid hurting the cornea.
There may be foreign body sensation or tears, so don't wipe it with your hands and pay attention to hygiene.
Don't wash your hair or take a bath. Never use eye cosmetics.
Within a week:
Wear an eye mask to protect your eyes when sleeping, and avoid the displacement of corneal flap caused by external force.
Don't smoke, don't drink, don't eat areca, and eat less irritating food. Watch less TV, computers, books and newspapers to avoid eye fatigue.
In order to prevent dust or foreign objects from entering the eyes, you can wear sunglasses, flat mirrors or goggles to go out.
Never swim or take a steam bath.
Within one month: avoid strenuous exercise or activities that may hurt your eyes. Don't drive or operate dangerous machines.
Life: Pay attention to hygiene and avoid excessive use of eyes.
Edit this paragraph of modern myopia surgery classification. The main surgical method is conventional lasik.
The principle of operation is to make lamellar corneal flap with pedicle on the corneal surface by using automatic microscopic corneal lamellar system. After the corneal flap is turned over, the excimer laser computer controls the multi-step sectional cutting of corneal stroma, and finally resets the corneal flap. This method preserves the integrity of corneal epithelium and anterior elastic layer, and uses 193 nm excimer laser to cut corneal stroma, thus avoiding the occurrence of haze after operation. This kind of surgical equipment is precise and expensive, which requires high surgical technology and sterile surgical environment and can only be performed in large hospitals with good conditions. At present, LASIK has become the most commonly used refractive surgery method, and it is widely used all over the world to take off glasses for many myopia and hyperopia patients. This technique is suitable for myopia patients within 1200 degrees.
Ultrathin lasik
Ultra-thin LASIK is a kind of LASIK surgery to thin corneal flap. Using French ultra-thin corneal flap manufacturing technology, the thickness of corneal flap is controlled at about 100 micron. For patients with the same corneal thickness, ultra-thin LASIK reduces the risk and further improves the safety of surgery because the corneal flap is thinner than ordinary LASIK. It combines the advantages of LASIK and EPI-LASIK, making the operation more suitable for people, and giving many patients with high height, thin cornea and routine LASIK the opportunity to take off their lenses. For patients who are suitable for LASIK surgery, if ultra-thin LASIK surgery is selected, more corneal stroma layer will be retained, and the safety and postoperative stability of the surgery will be higher. At present, ultra-thin LASIK has become the main refractive surgery method to replace conventional LASIK surgery.
Epi-lasik
The corneal epithelial flap made by special corneal epithelial knife (this knife can intelligently stop penetrating after cutting into the corneal epithelial layer, and then automatically separate the corneal epithelial layer from the underlying tissue smoothly) is only 50-60 microns thick, completely controlled by computer and automatic machinery, and the made epithelial flap is particularly flat. After laser cutting, the epithelial flap was reset and the operation was completed. It combines the advantages of LASIK and LASEK, and the visual quality after operation is greatly improved. Its long-term effect is better, the corneal thickness is saved, the correction range is wider, the safety is higher, and it has very attractive clinical value.
Q guided LASIK
Q-value-guided LASIK surgery carries out individual corneal ablation according to the aspherical characteristics of individual cornea, maintains the aspherical characteristics of cornea, and makes the treatment accuracy and effect develop rapidly. By adjusting the light zone, transition zone and treatment parameters more finely, more satisfactory surgical results can be obtained. Postoperative visual quality is better than conventional surgery, and it can also reduce glare and improve night vision. This is very positive for patients who need to drive at night.
Crystal surgery
The principle of the operation is to make a tiny incision on the edge of the patient's cornea, and implant a special intraocular lens into the anterior chamber or posterior chamber of the patient's eyeball. It is not necessary to wear the cornea and remove the original lens, so as to preserve the integrity and adjustment function of the physiological structure of the patient's eyeball. This operation actually moves the lens from the outside of the eye to the inside of the eye. Moreover, the operation is reversible. If you don't need this kind of intraocular lens, you can take it out with a minor operation. The surgical effect is good and the corrected refractive range is large. This technique is suitable for patients with ultra-high myopia of 1300-3000 degrees, astigmatism of more than 300 degrees, thin cornea and inability to perform laser surgery.
The types of lens surgery mainly include:
Iris clamping type in anterior chamber (ACL for short)
Posterior chamber type (ICL)
[2]
Editing Preoperative Consultation of Excimer Myopia Surgery —— Unveiling the Mystery of Excimer Surgery
Patients can have professional consultation in various ways, such as calling the hotline of professional hospitals, and professional consultants will answer your questions patiently and meticulously. In addition, you can also consult online through professional websites. Or go directly to the hospital to consult a professional doctor. By establishing a basic understanding of LASIK surgery, we can eliminate unnecessary mystery and fear of this surgery.
Preoperative initial diagnosis-safety check, rest assured diagnosis and treatment
Choose the right date to come to the hospital for the first visit, and the whole initial visit process will be carried out in an orderly manner under the guidance of the guiding doctor.
The first visit is mainly to check the patient's basic situation, and make a detailed examination and analysis of your eyes through various professional instruments to determine whether you are suitable for excimer laser surgery. Professional doctors can make a surgical plan according to everyone's analysis and examination data, and make a general prediction of the surgical effect. So this link is very important. In this link, doctors will screen out patients who are not suitable for surgery, such as some fundus lesions, diabetic patients, keratoconus, scar constitution and so on. If you pass this examination, it means that you are suitable for this operation. The safety of the operation must start from the preoperative examination to the end of the operation.
Professional doctors engaged in excimer surgery must have strict examination and approval qualifications and many years of surgical experience, and patients can decide whether to continue the operation according to the doctor's advice.
Preoperative follow-up-the second operation safety firewall
The main purpose of the follow-up visit is to verify the accuracy of the initial examination data, and to put another firewall on the safety of the operation through the detection of a series of professional equipment. And finally determine the surgical plan. The doctor will give you a comprehensive and detailed explanation of the whole operation arrangement, and explain the precautions on the day of operation and some protective measures after operation. You can determine the operation time and sign the informed consent form according to your own situation and doctor's advice. Experts especially reminded that preoperative examination must be very strict and taken seriously. As long as one test fails, you can't accept excimer surgery.
Undergo surgery-experience the process of removing excimer lens
On the day of operation, it is necessary to make arrangements according to the doctor's advice, such as wearing comfortable clothes, avoiding contact with alcohol, tobacco and other irritating substances and related drugs in advance, and not using cosmetics. The operation process takes about 15 minutes, and the actual time of using excimer laser is less than 30 seconds. You need a short rest after the operation. Doctors and nurses will take some professional protective measures to protect your eyes from being affected.
Postoperative care-gradually emerging in the Qing Dynasty.
Be sure to follow the doctor's advice and come to the hospital regularly after operation, so as to follow up the operation at any time. The doctor will have a set of detailed instructions on precautions and protective measures after operation. Surgical patients need to follow these instructions one by one. In addition, the hospital will also provide a perfect postoperative service system, so that patients can enjoy warm medical services at any time. [3]
What symptoms does this myopia laser surgery adapt to ① The patient has the requirement of taking off the lens.
② The age is over 18 years old (preferably over 20 years old).
③ The diopter is stable in recent two years.
④ Correction diopter range: myopia does not exceed 1500 degrees, astigmatism does not exceed 600 degrees, and hyperopia does not exceed 600 degrees.
⑤ anisometropia.
⑥ Current users of contact lenses: Soft lenses should be stopped for more than 2 weeks, hard lenses for more than 3 weeks, and OK lenses for more than 1-3 months.
⑦ Corneal thickness is greater than 450 um (depending on refractive state).
8 No active eye diseases, etc.