Myopia has become a world problem, and now with the popularity of myopia surgery, more and more people want to do myopia surgery.
Many people have a lot of worries before they have myopia surgery:
After myopia surgery, will there be sequelae?
Will I be blind or myopia rebound?
Is myopia surgery about moving a knife in the eye? What if I do it wrong?
……
Whether our vision is good or not is mainly related to the 3 structures in the eye - the cornea, the lens and the eye axis.
Most myopia is that the eye axis is too long, causing the light entering your eye to be imaged in front of the retina, making things unclear [1].
(Near View Note)
The eye axis of an adult is almost fixed and can only change two other structures – the cornea and the lens.
This is also where the myopia surgery is performed. Myopia surgery is to change the curvature of the cornea or lens and refocus light on the retina [2].
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 kinds of surgery are all "cutting" the cornea - using a laser knife to "cut" the cornea thin and correct vision.
Another type of myopia surgery is becoming more common: intraocular lens implantation (ICL), in which an intraocular lens (equivalent to a contact lens) is implanted in the eye to correct vision.
Next, we will talk about one by one.
Let's compare the cornea to a watermelon, and see how myopia surgery "cuts" the cornea step by step [3]:
1. LASIK surgery: corneal flap needs to be made
(Source: Network)
The surgical process can generally be divided into 3 steps:
1. Make corneal flaps (watermelon peel).
Corneal refractive surgery is mainly done in the corneal stromal layer, so the first step is to open the surface of the cornea, and this process is to make the 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.
Depending on the flap technique, surgery can be divided into two types:
Micro corneal knife + excimer laser surgery, commonly known as excimer laser surgery;
Femtosecond laser flap combined with excimer laser, commonly known as half-femtosecond surgery (FS-LASIK surgery). FS-LASIK surgery Because the corneal flap is made with femtosecond lasers, the corneal flap is thinner, more precise and smoother, and the safety is higher, so the corneal flap-related complications after FS-LASIK surgery have fewer complications and the postoperative corneal flap heals 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. Full laser surgery (T-PRK surgery): "no knife / no incision / no flap"
T-PRK surgery is mainly performed on the surface layer of the cornea, which is a superficial surgery.
Compared with the above FS-LASIK surgery, T-PRK surgery does not require the production of corneal flaps, and all operations can be completed in one step, so "no knife", "no incision" and "no flap".
The specific procedure of the operation is as follows:
1. Excimer laser to remove epithelial tissue
2. According to the excimer laser scanning matrix layer (watermelon), myopia is corrected
T-PRK surgery requires only one step to remove the corneal epithelium and matrix, does not require the production of corneal flaps, and does not form incisions or flaps on the cornea, so there will be no complications associated with corneal flaps after surgery, and the safety is higher [5].
(Source: Network)
T-PRK surgery has been suggested to be one of the safest and most appropriate options for myopic patients with thin corneas.
However, this procedure also has limitations and is generally suitable for myopia below 800 degrees [5].
3. Full femtosecond laser surgery (SMILE): no need to make corneal flaps, "fight the tiger across the mountain"
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 with the FS-LASIK procedure, because there is no need to make a corneal flap, the procedure becomes a two-step procedure:
Cut: Fight the tiger 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);
To 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, which can avoid surgical complications caused by making corneal flaps;
Avoid displacement of the corneal flap due to trauma, etc.
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. Intraocular lens implantation (ICL)
Intraocular lens implantation (ICL), in which an intraocular lens (equivalent to a contact lens) is implanted in 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:
Higher risk of intraocular infections 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.
(Source: Network)
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, suitable for their own is the best, according to the actual situation of the individual, consult the doctor's advice to choose.
From LASIK surgery and T-RPK surgery to full femtosecond laser surgery and intraocular lens implantation, the trend is:
Increasing automation;
The wounds left on the eyes are getting smaller and smaller;
Getting more and more expensive;
Overall, it's getting safer.
To sum up, the advantages and disadvantages of these procedures are:
In general, the general requirements for myopia surgery are [6]:
Age 18 years or older;
The degree of myopia is basically stable within 2 years (the degree of myopia increases by no more than 50 degrees per year);
Myopia ≤ 1200 degrees, astigmatism ≤ 600 degrees, farsightedness ≤ 600 degrees.
People with these conditions cannot have myopia surgery:
Active inflammatory reactions and infections in the eyes;
Insufficient thickness of the cornea;
Severe dry eye;
Cataracts, which have progressed to affect vision;
……
However, whether each person can do it, which kind of myopia surgery is suitable, or go to a regular hospital, check the various indicators of the eye, and make a decision with the doctor.
Myopia surgery is a mature procedure because the risk of side effects is small and controllable.
However, all surgeries are risky, and myopia surgery is no exception.
The side effects of different surgeries may vary from person to person [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 destabilizes the tear film.
This side effect is usually temporary and can be relieved by dripping artificial tears.
(2) Diffuse interlamellar keratitis
The postoperative incidence is 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 treatment, which basically does not have a great impact on life.
To add here, many people say that retinal detachment occurs 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 those who joined the military and public officials, but also many medical personnel and relatives have undergone myopia surgery.
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 Refractive Surgery Team from 2000 to 2001[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 equivalent to "cutting" off the degree of myopia of the eye;
Intraocular lens implantation is simply the addition of a contact lens to the eye.
If you still have unhygienic eye habits (such as excessive eye use) 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~
Reviewers:
Hu Liang
Deputy Chief Physician of Optometry Hospital Affiliated to Wenzhou Medical University
Zhang XianMei
Deputy Director of the Department of Ophthalmology, Affiliated Hospital of Hangzhou Normal University
Guo Chungang
Director and Chief Physician of the Department of Ophthalmology, Beijing You'an Hospital, Capital Medical University
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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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