“1、2、3...... In 3 seconds, the world went from hazy to clear and glasses were never needed again"
Every myopic person has such a dream of taking off his glasses, but the rumors about myopia surgery on the Internet are frightening.
● Does myopia surgery expert recommend it?
●After myopia surgery, will there be sequelae?
● Will I be blind or myopia rebound?
● Is myopia surgery about moving a knife in the eye?
●……
Regarding myopia surgery, almost everyone will ask these questions, today we will clarify them all at once.
Simply put, myopia surgery is to surgically change the curvature of the cornea or lens, so that light is refocused on the retina.
In order to better understand the "knife" operation of myopia surgery, you must first know these 1 points -
Whether our vision is good or not is mainly related to the cornea, lens and eye axis.
Most myopia is that the eye axis is too long, and the light entering your eye is imaged before the retina, resulting in unclear vision.
However, the eye axis of adults is almost fixed, and can only change the other 2 structures, that is, the cornea and lens.
In the process of people seeing things, the cornea and lens play an important role, of which:
● The cornea contributes the most to the refractive power of the eyeball, providing about 70% of the refractive force;
●The contribution of the lens to refractive force is lower than that of the cornea, less than half of the refractive force of the cornea.
Therefore, myopia surgery mainly operates on these two structures of the eye, by changing their curvature, so that the vision is clearly imaged on the retina.
Image source: Stand Cool Helo
(To explain here, myopia surgery is not a cure for myopia.) Most of the nearsightedness is true myopia, the eye axis becomes longer leading to blurred vision, most of the eye axis can not be changed after adulthood, myopia surgery is equivalent to making glasses into the eyes, the eyes are still myopic; here the focus is to remind people with high myopia, after surgery or to regularly check the eyes to avoid complications)
The 3 most commonly used myopia surgeries are corneal refractive surgery:
●LASIK surgery;
● Total laser surgery (T-PRK surgery);
● Full femtosecond laser surgery (SMILE surgery).
These 3 surgeries are to change the curvature of the anterior surface of the cornea to correct myopia, simply put, "cut" the cornea - using a laser knife to "cut" the cornea into a pair of "glasses" that suit you.
In addition to the above myopia surgery for the cornea, there is another type of myopia surgery that is becoming more common: lens implant surgery (ICL) – implanting an intraocular lens in the eye (equivalent to a hidden spectacle), which is reversible and allows the lens to be removed or replaced if necessary.
As mentioned above, corneal refractive surgery mainly moves the cornea.
This is because the cornea looks so thin, in fact, there are 5 layers of structure -
Depending on the location of the "knife", corneal refractive surgery can be divided into two categories: surface surgery and primary surgery.
●Surface surgery: all-laser surgery (T-PRK surgery);
● Primary surgery: LASIK surgery and SMILE surgery, which are mainly done in the corneal stromal layer (as shown in the figure above, the stromal layer in the cornea is the thickest layer of the cornea, with a thickness of 90% of the overall thickness, which is convenient for cutting [1]).
We compare the cornea to a watermelon, and how every myopia surgery is performed [3].
1. LASIK surgery
The most important feature of this surgery is that corneal flaps need to be made during the operation.
There are 2 types:
● Micro corneal knife + excimer laser surgery, that is, excimer laser in situ corneal grinding (LASIK surgery), which is relatively traditional;
● Femtosecond laser flap combined with excimer laser, commonly known as half-femtosecond surgery (FS-LASIK surgery).
(Source: Network)
The surgical process can generally be divided into 3 steps:
(1) Make corneal flaps (watermelon peel).
As mentioned above, corneal refractive surgery is mainly done in the corneal matrix layer, so the first step is to open the surface of the cornea, and the process is to make a corneal flap.
You can understand this: cut a round lid on the surface of the watermelon, not completely cut, connected by the peel, and then lift the peeled area up.
The 2 procedures mentioned above are mainly different in flap making techniques:
Compared with the traditional surgery of using a miniature corneal blade to make corneal flaps, FS-LASIK surgery has made corneal flaps with femtosecond lasers, which make corneal flaps thinner, more precise, smoother and safer, so there are fewer complications associated with corneal flaps after FS-LASIK surgery, and the postoperative corneal flaps heal faster.
(2) Grinding the corneal stromal layer (watermelon).
An excimer laser is used to polish the corneal matrix layer, which is the watermelon inside.
(3) Reducing the corneal flap (watermelon peel).
Then turn the corneal flap back and cover it in place, that is, put the watermelon peel back.
LASIK surgery is currently the most extensive myopia surgery in the world, and there is generally no obvious eye discomfort and rapid vision recovery after surgery.
At this time, some people will ask, will polishing the corneal stromal layer damage it?
Don't worry about this. Studies and practice have shown that fine plate layers in the corneal matrix are incised, which does not lead to intra-matrix opacification [4].
2. All laser surgery (t-PRK surgery)
Compared with the above FS-LASIK surgery, t-PRK surgery can complete all operations in one step, so "no knife", "no incision", "no flap" -
In general, the specific procedure of surgery is as follows:
(1) Excimer laser excision (cutting) of corneal epithelial tissue.
(2) Correct myopia according to the elastic layer and matrix (watermelon sac) before excimer laser cutting.
t-PRK surgery requires only one step to remove the corneal epithelial cell layer, the anterior elastic layer, and the superficial stromal layer, eliminating the need to make corneal flaps and not forming incisions or corneal flaps on the cornea, so there will be no complications associated with corneal flaps after surgery, and the safety is higher [5].
T-PRK surgery has been suggested to be one of the safest and most appropriate options for myopic patients with thin cornea.
However, this procedure also has limitations and is generally suitable for myopia below 800 degrees [5].
3. Full femtosecond laser surgery (SMILE)
Full femtosecond laser surgery, also known as smile surgery, does not require the creation of corneal flaps.
Through the femtosecond laser, the lens that needs to be removed is made directly in the corneal matrix layer, just like a tiger in the next mountain.
(Source: Network)
Compared to the FS-LASIK procedure, because there is no need to make corneal flaps, the procedure becomes 2 steps:
● Cut: Fight tigers across the mountain. A microlens is made with a femtosecond laser, and then an incision is made with a femtosecond laser (usually around the cornea, 2-4 mm in size);
● Take: Remove the cut corneal matrix.
Throughout the process, each person is entered in a computer with a different degree, and the computer automatically controls the thickness of the microlens to maintain the accuracy of the operation.
This benefit is:
● There is no need to make corneal flaps, and surgical complications caused by corneal flaps can be avoided;
● Avoid displacement of corneal flaps due to trauma;
The risks are:
● There may be a risk of incomplete intraoperative lens removal.
Full femtosecond laser surgery is less risky of corneal flaps than FS-LASIK surgery, but full femtosecond surgery may be slightly less effective in patients with large pupils.
4. Lens implantation surgery (ICL)
Lens Implant Surgery (ICL), in which an intraocular lens (equivalent to a contact lens) is implanted between the iris and your natural lens to achieve clear vision.
This surgery does not require cutting the cornea, and some people find that the cornea is not thick enough after examination to be unsuitable for corneal refractive surgery, which can be performed after the doctor's assessment.
The benefits of this surgery are:
● Reversibility, that is, intraocular lenses can be removed at any time after surgery.
The risks are:
● The risk of intraocular infection is higher due to intraocular manipulation;
● Because there is an implanted intraocular lens in the eye, the risk of complications such as cataracts, glaucoma, and uveitis is relatively high.
Myopia surgery is a very highly mature surgery in the clinic, with little trauma, fast recovery, and overall safety. But not the most expensive is the best, the one that suits you is the best.
From LASIK surgery and t-RPK surgery to full femtosecond laser surgery and lens implant surgery, the trend is:
• Increasing automation;
● The "wounds left on the eyes are getting smaller and smaller";
● Getting more expensive.
Overall, it's getting safer.
To sum up, the advantages and disadvantages of these procedures are:
In general, the general requirements for laser corneal refractive surgery are [6]:
● Age 18 years or older;
● The degree of myopia is basically stable in 2 years (the annual increase in myopia degree does not exceed 50 degrees);
● Myopia ≤ 1200 degrees, astigmatism ≤ 600 degrees, farsightedness ≤ 600 degrees.
People with these conditions cannot have myopia surgery:
● Active inflammatory response and infection in the eye area;
● Severe dry eye;
● Cataracts, which have progressed to affect vision;
● ……
But can each person do it? Which kind of myopia surgery is suitable, or go to a regular hospital, assess the risk and make a decision with the doctor.
Myopia surgery is a mature procedure because the risk of these side effects is small. However, all surgeries are risky.
Myopia surgery is no exception.
Different people may have different side effects from one person to the other, and the side effects of different surgeries may be different [7].
In the case of full femtosecond laser surgery (SMILE) surgery, possible complications are [7,8]:
(1) Dry eye
This is the most common complication because surgery destroys the stability of the tear film, etc.
This side effect is usually temporary and can be relieved by driping artificial tears.
(2) Diffuse interlamellar keratitis
The specific cause of an inflammatory response that may occur after myopia surgery is still unknown, with a postoperative incidence of 0.04 to 1.6%, and symptoms such as photophobia and vision loss may occur.
(3) Night glare, halo
Some people will have nocturnal glare, halos, etc. after myopia surgery. Usually resolves spontaneously after a few months.
As can be seen from the above, the postoperative complications of myopia surgery are relatively mild, and the doctors have rich experience in handling, which basically will not have a big impact on life.
Here to mention, many people say that the retina will fall off after myopia surgery.
Here's the debunking! Myopia surgery itself does not increase or decrease the risk of retinal detachment, but rather that high myopia itself is one of the high risk factors for retinal detachment.
Most nearsimplasias are axial myopia, i.e., the eye axis becomes longer and the retina is elongated, and the higher the degree, the more likely it is to develop peripheral retinal detachment [9].
Laser corneal refractive surgery has been performed in China for nearly 30 years – from the earliest hundreds of people per year, to 500,000 per year in 2003, and to about 1 million per year in 2018 [10].
Not only military personnel and public officials, but also many medical personnel and relatives have undergone myopia surgery.
Image source: Stand Cool Helo
In 2008, NASA approved corneal refractive surgery for astronauts and astronauts,[11] and four years later published a paper stating that astronauts' eyes were not affected after myopia surgery, which was a safe and effective alternative to contact lenses and spectacles.
After years of development, the effectiveness of myopia surgery has also been verified-
The U.S. Ophthalmic Technical Evaluation Board's 2000-2001 Refractive Surgery Team[13] reviewed 160 papers from 1968 to 2001 and screened 47 that were clinically significant for evaluation, covering 9 high-quality randomized controlled trials findings:
For myopia of moderate to low degrees (≤600 degrees), good naked-eye vision can be obtained after excimer laser surgery.
Rarely.
Adults over 18 years old with moderate and low myopia of less than 500 degrees, as long as the degree increase does not exceed 100 degrees in the first 2 years of surgery, generally rebound rarely occurs after surgery;
However, after myopia correction surgery, it is still possible to deepen myopia, because myopia surgery only corrects your previous myopia:
●Corneal refractive surgery is only equivalent to matching glasses to the cornea;
●Lens implant surgery is simply adding a contact lens to the eye.
If you still have bad eye habits (such as excessive use of the eyes, etc.) after surgery, myopia may continue to develop.
However, most patients undergoing excimer laser surgery and half-femtosecond laser surgery can be performed after the degree is stable before performing synergistic surgery.
The other one is the old flower. Like normal eyes, you will still be old after myopia surgery.
This is because: after the age of 45, presbyopia may appear, which is related to the aging of the lens. Laser surgery for myopia does not by itself make presbyopia more severe than in non-surgical populations [14].
Have the patience to see here...
Must have really seriously considered whether to do myopia surgery...
However, myopia surgery involves too many problems, and we have selected the main questions to answer.
Do you have any other questions about myopia surgery? Welcome to leave a comment in the comment area~
bibliography:
Ophthalmology. Human Guard Ninth Edition
Keratopathy Group, Ophthalmology Branch of Chinese Medical Association. Expert consensus on clinical diagnosis and treatment of laser corneal refractive surgery (2015). Chinese Journal of Ophthalmology. 2016.51（04）：249-254.
Refractive surgery. Eighth edition
[4] The state of the cornea after laser cutting
Hu Liang,Wang Qinmei. Key points and prospects of three all-laser corneal refractive surgery techniques[J]. Chinese Journal of Optometry and Vision Science,2016,18(4):193—198.
National Health Commission. Guidelines for the prevention and treatment of myopia.
[7] Chan C, Lawless M, Sutton G, et al. Small incision lenticule extraction (SMILE) in 2015. Clin Exp Optom. 2016;99(3):204-212.
[8] Kim TI, Alió Del Barrio JL, Wilkins M, et al. Refractive surgery. Lancet. 2019, 393(10185):2085-2098.
[9] Williams K, Hammond C. High myopia and its risks. Community Eye Health. 2019;32(105):5-6.
WANG Yan, SHI Weiyun, LI Ying. Rapid development and change of corneal refractive surgery in mainland China[J] . Chin J Ophthalmology,2020,56 (02): 81-85.
[11] Gibson CR. Effect of Microgravity on the Cornea of a Refractive Surgery Subject (Visual_Acuity). nasa.gov. 2008.
[12] Gibson CR, Mader TH, Schallhorn SC, et al. Visual stability of laser vision correction in an astronaut on a Soyuz mission to the International Space Station. Journal of Cataract and Refractive Surgery. 2012. August: 38(8):1486-1491.
[13] Sugar A, Rapuano CJ, Culbertson WW, et al. Laser in situ keratomileusis for myopia and astigmatism: safety and efficacy: a report by the American Academy of Ophthalmology. Ophthalmology. 2002, 109(1):175-187.
[14]https://americanrefractivesurgerycouncil.org/how-long-does-lasik-last/
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