“In 1, 2, 3…3 seconds, the world goes from hazy to clear, no need for glasses anymore”
Everyone who is short-sighted has such a dream of taking off their glasses, but the rumors about myopia surgery on the Internet are scary-
● Is myopia surgery recommended by a specialist?
● Will there be any sequelae after myopia surgery?
● Will I be blinded or myopia will rebound?
●Is myopia surgery just a knife on the eye?
●…
A few questions that almost everyone asks about myopia surgery, today we will clarify them all at once.
Simply put, myopia surgery involves surgically altering the curvature of the cornea or lens to refocus light on the retina.
In order to better understand the “moving knife” operation of myopia surgery, you must first know this one point-
Our vision is mainly related to the cornea, lens and axis of the eye.
Most nearsightedness is excessive axial length, where light entering your eye is imaged in front of the retina, causing blurred vision.
However, the axis of an adult’s eye is almost fixed and can only change the other two structures, the cornea and the lens.
The cornea and lens play an important role in how people see, including:
●The cornea contributes the most to the refractive power of the eyeball, providing about 70% of the refractive power;
●The lens contributes less to the refractive power than the cornea, less than half the power of the cornea.
Myopia surgery mainly operates on these two structures of the eye, and by changing their curvature, the vision can be re-imaged on the retina.
Image source: Zhanku Hailuo
(Explain here, myopia surgery is not a cure for myopia. Most myopia is true myopia, blurred vision caused by the lengthening of the eye axis, most of the eye axis in adulthood is fixed and cannot be changed, myopia surgery It is equivalent to putting glasses into the eyes, but the eyes are still myopic; the key point here is to remind people with high myopia to regularly check their eyes after surgery to avoid complications)
The three most common types of myopia surgery today are refractive surgery:
●LASIK surgery;
● Total Laser Surgery (T-PRK Surgery);
● Full Femtosecond Laser Surgery (SMILE Surgery).
These three surgeries are to correct myopia by changing the curvature of the anterior surface of the cornea. Simply put: “shaved” the cornea – using a laser knife to “shave” the cornea into a pair that suits you “Glasses”.
In addition to the corneal myopia surgery above, there is another type of myopia surgery that is becoming more common: implantation of the lens (ICL), in which an intraocular lens is inserted into the eye ( Equivalent to contact lenses), this procedure is reversible, allowing 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, is actually made up of 5 layers-
According to the position of the “moving knife”, corneal refractive surgery can be divided into 2 categories: superficial surgery and primary surgery.
Topical surgery: total 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 image above, the middle layer of the cornea is the thickest layer of the cornea The thickness accounts for 90% of the overall thickness, which is convenient for cutting [1]).
We compare the cornea to a watermelon, and how each type of myopia surgery works[3].
1. LASIK surgery
The main feature of this procedure is that a corneal flap is made during the procedure.
Includes 2 types:
● Microkeratome + excimer laser surgery, that is, laser in situ keratomileusis (LASIK surgery), which is relatively traditional; p>
● Femtosecond laser flap making combined with excimer laser, commonly known as half-femtosecond surgery (FS-LASIK surgery).
(Source: Internet)
The surgical procedure can generally be divided into 3 steps:
(1) Make corneal flap (watermelon rind).
As mentioned above, corneal refractive surgery is mainly done in the corneal stromal layer, so the first step is to lift the corneal surface layer, and this process is making a corneal flap.
You can understand that: cut a circular cover on the surface of the watermelon, not cut it completely, connect it through the rind, and then lift up the peeled area.
The two surgeries mentioned above are mainly different in flap making techniques:
Compared to the traditional surgery using a microkeratome to create a corneal flap; FS-LASIK surgery uses a femtosecond laser to create a corneal flap, the corneal flap is thinner, more precise and smoother , Higher safety, so fewer complications related to corneal flap after FS-LASIK surgery, and faster postoperative corneal flap healing.
(2) Grinding the corneal stroma (watermelon flesh).
Use an excimer laser to polish the corneal stroma, which is the watermelon flesh inside.
(3) Reset the corneal flap (watermelon rind).
Flip the corneal flap back and cover it in place, that is, put the watermelon rind back.
LASIK surgery is currently the most widely performed myopia surgery in the world. There is generally no obvious eye discomfort after surgery, and vision recovery is quick.
At this time, some people will ask, will grinding the corneal stromal layer damage it?
Don’t worry about that. Research and practice have shown that the incision of the fine lamella in the corneal stroma will not lead to intrastromal opacity[4].
2. Full 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”——
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Generally speaking, the specific procedure of surgery is as follows:
(1) Excimer laser ablation (ablation) of corneal epithelial tissue.
(2) Correct myopia by cutting the elastic layer and matrix (watermelon sac) by excimer laser.
t-PRK surgery removes the corneal epithelial cell layer, the prestretch layer and the superficial stroma in one step, no corneal flap, no incision or corneal incision Therefore, there will be no corneal flap-related complications after surgery, and the safety is higher[5].
Studies suggest that t-PRK surgery is one of the safest and most suitable options for myopic patients with thin corneas.
However, this surgery 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 a corneal flap.
The lens that needs to be removed is made directly in the corneal stromal layer by femtosecond laser, just like fighting a tiger across a mountain.
(Source: Internet)
Compared to FS-LASIK surgery, because there is no need to make a corneal flap, this procedure becomes a 2-step procedure:
● Cut: Fighting tigers across mountains. A microlens is made with a femtosecond laser, and an incision is made with the femtosecond laser (usually at the periphery of the cornea, 2-4 mm in size);
● Removal: Removal of the excised corneal stroma.
In the whole process, each person’s different degrees are input into the computer, 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 corneal flaps;
● Avoid corneal flap displacement due to trauma;
The risks are:
● There may be a risk of incomplete lens extraction during surgery.
Full femtosecond laser surgery has less risk of corneal flap than FS-LASIK surgery, but full femtosecond surgery may be less effective in patients with larger pupils.
4. Implantation of the Lens (ICL)
Intraocular lens surgery (ICL) is a procedure in which an intraocular lens (equivalent to a contact lens) is inserted between the iris and your natural lens, resulting in clear vision.
This procedure does not require cutting the cornea, and some people find that the cornea is not thick enough after examination to be suitable for corneal refractive surgery, which may be performed after evaluation by a doctor.
The benefits of this procedure are:
● Reversible, which means the IOL can be removed at any time after surgery.
The risks are:
● Due to the operation inside the eye, there is a high risk of infection in the eye;
● Because of the intraocular lens implanted in the eye, the risk of complications such as cataracts, glaucoma, and uveitis is relatively high.
Myopia surgery is a very clinically mature surgery, with little trauma, quick recovery, and overall safety. But not the most expensive is the best, it is the best that suits you.
From LASIK surgery, t-RPK surgery to full femtosecond laser surgery, lens implant surgery, the changing trend is:
● Increasingly automated;
● “smaller and smaller wound” on the eye;
● Getting more expensive.
In general, it’s getting safer.
To summarize, the advantages and disadvantages of these procedures are:
In general, the general requirements for LASIK are [6]:
● Age 18+;
● The degree of myopia is basically stable within 2 years (the increase in the degree of myopia does not exceed 50 degrees per year);
● Myopia ≤ 1200 degrees; astigmatism ≤ 600 degrees; hyperopia ≤ 600 degrees.
Persons with these conditions cannot have nearsighted surgery:
● Active inflammation and infection in the eye;
● severe dry eye;
● cataracts that have progressed to the point of affecting vision;
● …
But can everyone do it specifically? Which myopia surgery is suitable, or go to a regular hospital to make a decision together with the doctor after evaluating the risk.
Myopia surgery is considered a full-fledged procedure because of the low risk of these side effects. However, all surgeries have risks.
Myopia surgery is no exception.
Different people are different, and different surgery may have different side effects [7].
Take full femtosecond laser surgery (SMILE) surgery as an example, the possible complications are [7,8]:
(1) Dry Eye Syndrome
This is the most common complication, as surgery destabilizes the tear film, etc.
This side effect is usually temporary and can be relieved with artificial tears.
(2) Diffuse interlayer keratitis
An inflammatory reaction that may occur after myopia surgery, the exact cause is still unclear, the postoperative incidence rate is 0.04~1.6%, and there may be symptoms such as photophobia and decreased vision.
(3) Night glare, halo
Some people experience nighttime glare, halos, etc. after myopia surgery. It usually resolves on its own after a few months.
It can be seen from the above that the complications after myopia surgery are relatively mild, and the doctors have rich experience in dealing with them, which will basically not have a big impact on life.
Here, as an extra, many people say that retinal detachment will occur after myopia surgery.
Rumours to be debunked here! Myopia surgery itself does not increase or decrease the risk of retinal detachment, but high myopia itself is one of the high risk factors for retinal detachment.
Most myopia is axial myopia, which means that the eye axis becomes longer and the retina is elongated, and the higher the degree, the more prone to peripheral retinal detachment [9].
Laser corneal refractive surgery has been carried out in China for nearly 30 years – from the earliest hundreds of patients per year, to 500,000 per year in 2003, and 100 per year in 2018 about 10,000 cases [10].
Not only military personnel and public officials, but also many medical personnel and relatives have undergone myopia surgery.
Image source: Zhanku Hailuo
In 2008, NASA approved corneal refractive surgery for astronauts and space crews [11], and four years later published a paper saying: After myopia surgery , the astronaut’s eyes are not affected, this operation is a safe and effective alternative to contact lenses and frame glasses[12].
After years of development, the effectiveness of myopia surgery has also been verified——
American Ophthalmology Technology Evaluation Committee 2000-2001 Refractive Surgery Group[13] reviewed 160 papers from 1968 to 2001, and screened 47 papers with sufficient clinical significance for evaluation, Covers 9 high-quality RCT findings:
For myopia of moderate to low degree of myopia (≤600 degrees), good uncorrected vision can be obtained after excimer laser surgery.
Rarely.
Adults over the age of 18 with moderate or low myopia less than 500 degrees, as long as the degree does not increase by more than 100 degrees within 2 years before surgery, generally rarely rebound after surgery;
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However, after myopia correction surgery, it is still possible to deepen the degree of myopia, because myopia surgery only corrects your previous degree of myopia:
● Corneal refractive surgery is only equivalent to putting glasses on the cornea;
●Lens implant surgery is simply the addition of a contact lens to the eye.
If you still have bad eye habits (such as excessive eye use, etc.) after surgery, myopia may continue to develop.
However, most patients undergoing excimer laser surgery and semi-femtosecond laser surgery can undergo enhanced surgery after the degree is stable.
The other is presbyopia. As with normal eyes, you will still be presbyopic after nearsighted surgery.
This is because: after the age of 45, presbyopia may occur, which is related to the aging of the lens. Laser myopia surgery by itself does not make presbyopia worse than non-surgical populations[14].
Have the patience to see here…
I must have seriously considered myopia surgery…
However, myopia surgery involves so many questions, we’ve chosen the main ones to answer.
Do you have any other questions about myopia surgery? Welcome to leave a comment in the comment area~
References:
[1] Ophthalmology. Human Health Ninth Edition
[2] Keratology Group of 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.
[3]Refractive Surgery. Eighth Edition
[4]The state of the cornea after laser cutting
[5] Hu Liang, Wang Qinmei. Three technical points and prospects of all-laser corneal refractive surgery [J]. Chinese Journal of Optometry and Vision Science, 2016, 18(4): 193-198.
[6] 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.
[10] Wang Yan, Shi Weiyun, Li Ying. Rapid development and changes of corneal refractive surgery in my country [J] . Chinese Journal of 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:https://americanrefractivesurgerycouncil.org/how-long-does-lasik-last/
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