Ophthalmologist's reminder: Not everyone can undergo laser | corneal | surgery for myopia

Editor's note: June 6, 2023 is the 28th national "Love Eye Day". This year's theme is "pay attention to general eye health". The eye is one of the most important senses of human beings, and eye health is also an important part of national health. In order to welcome the "Eye Love Day", this newspaper launched a special plan to popularize the knowledge of eye protection and eye love to the public, to help readers pay attention to eye health and protect the "eye" color world.

Every nearsighted person has a dream of taking off their glasses. Many people hope to say goodbye to their glasses forever through myopia surgery. However, ophthalmologists remind that there are many contraindications for myopia surgery, and one should not blindly follow the trend.

Myopia surgery needs to meet a number of conditions

Multiple conditions must be met for myopia surgery

Wang Ningli, the leader of the National Blindness Prevention Technology Guidance Group and the director of the Ophthalmology Center of Beijing Tongren Hospital affiliated with Capital Medical University, said that myopia surgery, as the name suggests, is to restore normal vision to the population through surgery. Since the success of the world's first excimer laser myopia surgery in 1988, the technology of myopia surgery has continuously developed and improved over the past few decades. "As long as the indications are strictly controlled, the safety of surgery is guaranteed," said Wang Ningli.

But Wang Ningli also emphasized that not all myopic individuals are suitable for surgery, and decisions need to be made jointly by doctors and patients based on the different situations of each myopic individual.

So, what kind of person can undergo myopia surgery? Xu Chenchen, Deputy Director of Excimer Laser Department at Wenzhou Medical University Affiliated Ophthalmology Hospital, explained that suitable individuals for myopia surgery are required to be at least 18 years old and have a stable degree of myopia in the past two years, with an annual increase of no more than 50 degrees; Corneal refractive surgery can correct myopia of 50-1200 degrees, hyperopia of no more than 600 degrees, and astigmatism of no more than 600 degrees; No serious corneal diseases, women are not in pregnancy or lactation.

Two types of myopia surgeries are suitable for different populations

Zhang Fengju, Director of the Medical Optometry Department at Yizhuang Campus of Beijing Tongren Hospital, introduced that currently, the mainstream myopia surgery in China mainly includes two categories: corneal refractive surgery and intraocular refractive surgery. The refractive surgery for the cornea includes epithelial excimer laser corneal surface cutting, femtosecond laser assisted corneal flap fabrication combined with excimer laser corneal stromal grinding, and femtosecond laser small incision corneal stromal lens removal. These three surgeries can be understood as creating a "glasses" on the human cornea. And intraocular refractive surgery can be understood as installing a special type of contact lens into the eye.

"The refractive surgery for the cornea is achieved through laser," said Zhang Fengju. The basic principle is to artificially cut off a part of the corneal tissue similar to a "convex lens" on the cornea of the eye, thereby creating a "concave lens", which is the shape of a small eyepiece cut on the eye.

"The refractive surgery for the cornea involves laser cutting of corneal tissue to change corneal curvature and refractive index, which belongs to 'subtraction' surgery." Peng Yanli, Vice President of Chongqing Aier Ophthalmology Hospital, said that intraocular refractive surgery does not change corneal morphology, similar to implanting contact lenses in the eye, and belongs to 'addition' surgery. "It is generally recommended that individuals with a myopia degree of 600 degrees or above, thin corneas, and poor corneal morphology, opt for intraocular refractive surgery, while those with medium to low myopia, thick corneas, and good corneal morphology opt for corneal refractive surgery," she said.

During an interview with reporters, Zhang Yan, the chief physician of the Clinical Medical Center of the Ophthalmology Department of Shanghai First People's Hospital, introduced that SMILE, commonly known as "full femtosecond", has a surgical incision of only 2.0 millimeters and less interference with corneal tissue and nerves. The surgical time, experience, and postoperative effect are relatively good. However, "full femtosecond" can only treat myopia up to 1000 degrees and astigmatism up to 500 degrees. FS-LASIK, commonly known as "half femtosecond", can correct myopia up to 1200 degrees and hyperopia up to 600 degrees. However, the incision circumference is more than 10 times that of "full femtosecond", and the degree of corneal biomechanical changes and dry eye after surgery is higher than that of "full femtosecond". Trans-PRK is particularly suitable for patients with low degree and thin cornea, but postoperative pain is severe and recovery and medication time is long. Doctors will develop personalized surgical plans based on the patient's specific examination results.

It should be noted that myopia surgery is not a one-time solution. Li Shiming, director of the Clinical Epidemiology and Evidence Based Medicine Joint Teaching and Research Office at Capital Medical University and chief ophthalmologist at Beijing Tongren Hospital, reminds that myopia surgery can only correct the degree of myopia that people already have, rather than prevent myopia from occurring again. If postoperative attention is not paid to scientific eye use, excessive eye use may still lead to myopia again. Therefore, it is necessary to use the eyes scientifically and try to avoid the rebound of myopia.

Multiple examinations and training are required before surgery

In order to make myopia surgery safer and more effective, various examinations and training should be performed before surgery.

Before undergoing myopia surgery, a series of preoperative examinations should be conducted to first exclude individuals with eye diseases such as keratoconus, fundus diseases, glaucoma, and severe amblyopia. Secondly, more than ten tests, including optometry, visual function, cornea, pupil, intraocular pressure, and fundus condition, are required before surgery.

"Doctors develop scientific surgical plans through comprehensive and detailed examinations to ensure safe surgery," said Zhang Fengju. Prior to surgery, there is also eye coordination training, mainly including gaze training, non avoidance training, strong light training, and eye opening training.

Xu Chenchen said that it is necessary to stop wearing contact lenses in advance before surgery. The most common soft contact lenses need to be stopped for 2 weeks, hard contact lenses need to be stopped for 3 weeks, and OK lenses need to be stopped for more than 3 months.

Due to the use of eye drops during the preoperative examination process, the pupils may enlarge, the ciliary muscles may become paralyzed and relaxed, and the examinee may experience temporary photophobia and unclear vision, which may affect driving. Therefore, Xu Chenchen suggests not driving to the hospital on the day of the examination.

Don't neglect protection and follow-up after surgery

After the surgery, you can immediately see a clear world, which is truly exciting. But Xu Chenchen also reminded that postoperative care should not be ignored.

This includes avoiding water in the eyes as much as possible within one week after surgery, and paying special attention when washing face, shower, and hair; Within one week after surgery, avoid prolonged reading, watching TV, or playing computer games, balance work and rest, and develop a scientific eye habit. Within two weeks after surgery, do not engage in competitive sports such as basketball, football, boxing, etc; Also, do not use cosmetics or perfume, gel water, etc. to avoid chemical substances sprayed into the eyes. Within one month after surgery, do not eat spicy or alcoholic foods, and do not smoke or drink alcohol. Not swimming in the water within 3 months after surgery.

"After surgery, artificial tears without preservatives should be used as a routine, four times a day, for at least one month." Zhang Fengju said that after three months of surgery, when going out, sunglasses should be worn to block wind, strong light, and ultraviolet radiation, and the number of blinks should be consciously increased appropriately to protect the stability of tear film function.

The medication and follow-up examination after myopia surgery are directly related to the recovery effect of the surgery. Experts such as Zhang Fengju have stated that postoperative medication must strictly follow the doctor's advice and not blindly increase or decrease the dosage. The time for re examination is generally one day, one week, one month, three months, six months, and one year after the surgery, and routine re examination at the hospital is required at these time points. After surgery, if there is eye trauma, sharp decline in vision, eye pain, elevated intraocular pressure, etc., timely medical attention should also be sought.

Presbyopia can also have corrective surgery.

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Presbyopia can also undergo corrective surgery

In daily life, presbyopia affects people's visual state. Like myopia, it can be corrected by wearing glasses, and like myopia, it can be removed by surgery.

There are various surgical methods for presbyopia, including laser correction and lens replacement. "Laser correction surgery for presbyopia patients can use femtosecond laser and excimer laser to solve the problems of myopia and presbyopia," said Chen Shihao, director of the Clinical Center for Refractive Surgery at Wenzhou Medical University Affiliated Eye and Vision Hospital.

Laser correction surgery for presbyopia is suitable for people with myopia degree less than or equal to 800 degrees, astigmatism degree less than or equal to 400 degrees, and hyperopia degree less than or equal to 500 degrees.