Currently, the prevalence of myopia in China is 33%, which is 1.5 times the world average of 22%. Myopia has become the fourth most common blindness after cataract, glaucoma and diabetic eye disease. The common symptom of myopia is blurred vision near and far, which has a great impact on the life and work of myopic patients, and it is extremely inconvenient to wear various glasses. Therefore, laser myopia surgery has become the most popular surgery in ophthalmology.
At present, there are two main types of laser surgery applied to refractive correction, namely Lasik and Lasek surgery with excimer laser and all-laser and all-femtosecond surgery with femtosecond laser.
Excimer laser in situ keratomileusis (LASIK): the dominant procedure at present. The key technique is to make a corneal flap with a tip using a mechanical microkeratome, perform laser cutting on the corneal stromal bed, and then reset the corneal flap.
Features: No postoperative irritation, stable refractive status, and rapid recovery of effective vision.
Advantages: The corneal epithelial layer and anterior elastic layer are preserved, in line with corneal barrier physiology, and there is basically no Haze (subcleral clouding) after surgery.
Major complications.
1. Medical complications.
(1) Corneal flap complications: relatively large corneal flap thickness error, corneal flap incompleteness, fragmentation, freeing, and buttoning.
(2) Corneal dilatation, conical cornea.
(3) Haze (less).
(4) Corneal infection.
(5) Dry eye.
(6) Optical complications: postoperative decrease in visual quality. Increased higher order aberrations, decreased night vision, glare, halos, etc.
Excimer laser epithelial flap subsurface keratomileusis (LASEK): The key technique is to create an intact epithelial flap that can cover the corneal stroma immediately after laser cutting, based on the pathophysiological basis of the integrity of the corneal epithelial basement membrane and the activity of the epithelial flap organelles.
Advantages.
1, mechanical protective effect.
2. blocking the action of cytokines in the tear fluid on the corneal stroma, including reduction of stromal cell activation, proliferation.
3, reduction of Haze appearance (relative to PRK).
4, reduction of refractive regression.
5.Complications of LASIK corneal stromal flap are completely avoided.
Disadvantages: Relative to LASIK, postoperative irritation symptoms and Haze are slightly more severe. It is generally advocated for mild refractive errors.
Femtosecond laser.
Higher precision. These include “all-laser” surgery (femtosecond laser + excimer laser), “all-femtosecond” surgery (stromal lenticule resection, FLEx), and micro-incision “all-femtosecond laser” surgery (micro-incision stromal lenticulectomy, SMILE). Femtosecond laser is a cutting-edge technology in the field of laser ophthalmology and was originally used by the US military as a “mystery light”. Long before it was introduced to the market, developed countries such as the U.S. and the U.K. had been performing flap-based laser surgery on fighter pilots and Marines, with priority acceptance by special forces soldiers. In the United States, the FDA (U.S. Food and Drug Administration) and NASA (National Aeronautics and Space Administration) authoritative certification for astronaut vision enhancement, nearly 1 million Americans each year through the femtosecond laser to improve vision.
”All laser” surgery (femtosecond Lasik, semifemtosecond): The key technology is to use a femtosecond laser rather than a mechanical microkeratome to make a tipped flap, cut the flap on the corneal stromal bed, and then reset the flap. Compared to mechanical microkeratome flap making, femtosecond laser flap making is more accurate, reliable, safer, less discrete, less corneal flap complications, thinner flaps can be made, such as mechanical microkeratome thin corneal flap The thickness of the flap can be 90~100μm, while the femtosecond laser can make a flap of 70~80μm; the precise positioning and fine cutting of the femtosecond laser technology has created the “full femtosecond” laser surgery mode.
”Femtosecond” surgery (Femtosecond laser corneal stromal lenticule removal).
The key technology is that the entire myopia surgery is performed with a femtosecond laser, i.e., the laser flap and/or lens removal in the corneal stroma is performed with the same femtosecond laser. In the field of refractive surgery, this refers specifically to FLEX (stromal lens excision) and SMILE (femtosecond microincision stromal lens excision). In the former, a corneal flap is made and the stromal lens tissue is removed. In the latter, no flap is made and only a small 4 mm incision is used to remove the stromal lens tissue. The small incision without corneal flap completely avoids the complications of corneal flap. It reduces the risk of medical-acquired infections and helps to preserve the biomechanical integrity of the cornea and reduce the risk of corneal dilation. Patients can barely hear the noise of the laser etc. nor smell a little burnt odor (which excimer laser surgery has), reducing intraoperative panic.
Disadvantages: Slightly more difficult to operate on for mild myopia.
Differences between “all-laser” surgery and traditional excimer laser myopia (Lasik) surgery.
For many people who want to have myopia surgery, it is not always clear what the differences are between femtosecond laser and traditional excimer laser. In layman’s terms, excimer myopia surgery (Lasik) uses a mechanical microkeratome to open the cornea and then the excimer laser, while all-laser surgery, also known as “knifeless surgery”, uses a femtosecond laser to open the cornea and then the excimer laser. In traditional laser myopia surgery, 80% of the risk of surgery is in the process of making the flap, because the traditional flap making process is done by a human operated metal keratome, human error and mechanical failure cannot be controlled. The “femtosecond laser” flap making technology, instead of the traditional surgical flap making metal corneal knife, is replaced by a fully computer-controlled femtosecond laser flap making, making a qualitative breakthrough in the safety of the flap making process.
The difference between “all-femtosecond” surgery and “all-laser” surgery.
”All-Laser surgery uses the femtosecond laser only to create the flap, and then uses the excimer laser to perform sub-flap ablation after the flap is lifted to complete the treatment of myopia. “The procedure provides better quality of vision and has less impact on the biomechanical elasticity of the cornea. In particular, the micro-incision “all-femtosecond laser” surgery (small incision stromal lenticule resection), with an incision of only 4 mm and no corneal flap, completely eliminates intraoperative and postoperative complications of corneal flaps. It helps to preserve the biomechanical integrity of the cornea and reduces the risk of corneal dilation. Patients can barely hear the noise of the laser or smell the scorching smell (which excimer laser surgery has), reducing intraoperative panic.
Seven advantages of “femtosecond laser” surgery.
1, femtosecond flap, no damage surgery safer: femtosecond laser is through the laser to achieve the photodynamic blasting of corneal tissue, in less than 30 seconds of the production of corneal flap process on the corneal tissue without damage, the safety of greater improvement.
2, uniform flap making, more perfect vision after surgery: Femtosecond laser can precisely open the molecular chain of eye tissue, making a more uniform and perfect corneal flap, avoiding medical aberration, avoiding glare and blurring that only occurs in foggy days, rainy days and night driving and other visual conditions, allowing myopic patients to obtain a more perfect visual quality.
4. Embedded occlusion, more accurate corneal flap reset. Femtosecond laser flap is embedded with the stroma of the eye in an “underground manhole cover” type of occlusion, so that the flap can be reset easily and tightly, without misalignment, and without complications such as broken flap and button flap.
4, micron precision, 100 times more accurate: Femtosecond laser can control the accuracy of corneal flap making within 10~15 microns, femtosecond higher safety speaks for itself.
5.Knife-free surgery, eliminating medical source infection: Femtosecond laser knife-free surgery makes the surgery on human cornea completely goodbye to the lamellar knife, and the occurrence of cross-infection during the surgery becomes history.
6. SMILE completely avoids the complications of corneal flap. It helps to retain the integrity of corneal biomechanics and reduce the risk of corneal dilation.
7. Wide indications and wider correction range: Femtosecond laser surgery is not affected by corneal curvature, which is a great blessing for myopic friends whose myopia is too deep or whose corneas are too thin to receive traditional laser surgery.
Femtosecond laser is suitable for people
All patients who are suitable for myopia surgery can undergo this procedure. In the past, there were five categories of people who could not undergo traditional myopia surgery can choose femtosecond all-laser surgery.
Its scope has also been expanded, mainly for the following.
1. 10% of patients who previously could not undergo myopia surgery because of thin corneas and high myopia can undergo myopia surgery with femtosecond laser flap making.
2, previously because of small eye fissure, small corneal diameter, flat corneal people, and can not use mechanical metal knife to make corneal flap people can also do femtosecond laser.
3, Femtosecond laser is also the first choice for augmentation surgery after undercorrection and overcorrection after normal myopia surgery.
4, for patients who are afraid of cutting the cornea with a mechanical metal corneal lamellar knife is the most suitable for this surgery.
5.For those who have high requirements for surgical results, it is recommended to do femtosecond laser as well.
Indications for conventional laser keratomileusis (Lasik, Lasek, all-laser, all-femtosecond).
1.Patients with refractive error aged 18 to 60, who are mentally and psychologically healthy and have a desire for lens removal and reasonable expectations.
2, reasonable refractive error range: +6 ~ -12D, column lens ≤ +6D.
3.The refractive error is relatively stable in the past 2 years.
4.The corneal thickness is appropriate.
5.No acute ocular infection or autoimmune disease.
6.Exclude cone cornea.
The essence of all-femtosecond laser surgery.
It not only improves the overall appearance and eliminates the inconvenience of wearing frame glasses and contact lenses, but also has the advantages of less damage, high accuracy, predictability, less complications and wide indications. The application of the all-femtosecond laser in refractive eye surgery has enabled mankind to truly achieve “knifeless surgery” in the cornea, and to make the leap from “all-laser” to “all-femtosecond” surgery. The essence of all-femtosecond laser is minimally invasive or even non-invasive, fine or even exquisite with “immediate” vision recovery, gentler, safer and more precise surgery.