What is considered normal visual acuity?
A: Under normal circumstances, when a person is 3 years old, the eye is not fully developed and is in a farsighted state, and its normal naked eye vision is 0.6; when it first enters school age, it is still in a mildly farsighted state, and its normal naked eye vision is 0.8~1.0. Thus, it can be seen that the normal vision of children in the medical sense is not necessarily 1.0, let alone 1.2, 1.5 or even 2.0. The visual acuity higher than 1.0 is called hyperopia, because the refractive medium is transparent and the retinal function of the fundus is good, and the resolution of objects can reach more than 1.0. However, hyperopia is not what we are looking for in optometry, and people with hyperopia do not have any advantage in quality of life compared to normal vision people except for taking advantage when applying for pilot jobs.
Medical science is more concerned with corrected visual acuity, and normal corrected visual acuity for adolescents is generally above 1.0. Corrected visual acuity below 0.8 is called amblyopia, which is a developmental limitation of the visual system and requires early medical attention for treatment.
What is optometry?
A: In layman’s terms, it is the examination of the refractive state of the eye. The refractive state of the human eye is divided into myopia, hyperopia, astigmatism, etc., which can only be accurately known through optometry. Optometry is also divided into objective optometry and subjective optometry, the former does not require the subject to identify the visual marker, through the judgment of the optometrist can be completed, while the latter requires the cooperation of the subject and optometrist to complete together. Generally speaking, objective optometry comes first, subjective optometry comes second, and the final prescription is based on the results of subjective optometry.
As mentioned earlier (see question 3), the human eye is a highly sophisticated camera, capable of seeing both near and far. When myopia increases, no matter how much the “lens” is focused, seeing far away is blurred. But it is worth noting that when children just appear low myopia, they can compensate for refractive error by squinting to increase the depth of focus, and can barely see as far away as the blackboard, but this is at the cost of visual fatigue, the results can be imagined. Therefore, parents should never make subjective assumptions about their children’s myopia, nor should they wait until their children can’t really see before coming to the clinic. Experts recommend that children and adolescents have a dilated eye exam at least once every six months. (A friendly reminder to avoid the summer and winter peak seasons for optometry at our hospital)
The correct medical optometry procedure for children and adolescents should be: Dilated pupil – computerized optometry – shadow vision optometry – primary optometry.
Should myopic children wear glasses?
A: The decision to wear glasses for myopia needs to be made after integrating various factors such as refractive error, binocular balance, eye position, accommodation, and accommodation. Generally speaking, low myopia that meets both bare eye vision of 0.6 or more and myopia of 75 degrees or less can be temporarily eliminated without glasses, but if there is exotropia, glasses are required. For medium and high myopia, appropriate glasses can improve the quality of vision required for daily study, work and life. At high levels (greater than 600 degrees), the first glasses are not required to be fully corrected, but to tolerate the degree, and then be fully corrected after adaptation. The principle of astigmatism correction is not to match asymptomatic astigmatism, and to try to match symptomatic astigmatism even if the degree is low. If you have a high degree of astigmatism, you can start with a low prescription and then adjust it after adaptation.
Will myopia get deeper after wearing glasses?
A: Some parents may hold the stereotype that “the earlier you wear glasses, the closer you get” and refuse to get glasses for their children. In fact, this is a blackmail statement, is the parents to meet their own subjective will performance, no scientific basis. Scientifically, the prescription should be based on the results of the optometry, combined with the visual acuity requirements, eye position, eye muscle movement, whether there is amblyopia and other comprehensive considerations. Several major factors in the occurrence of myopia have been introduced in the previous article, and the correct way of wearing glasses under medical optometry does not accelerate or deepen myopia.
Which myopic eyes need to be worn frequently after prescription?
A: Wearing glasses addresses two issues: the actual need to see far and the need to maintain the eye. If there is no problem of hidden strabismus and visual fatigue of the eye, then it depends on the actual need to see far: low myopia, that is, below 300 degrees, without astigmatism, can wear glasses for seeing far, and can be worn without them for seeing near. Greater than 300 degrees of moderate to high myopia normal close reading is also owed to clear, look far to wear, look close to also wear. If there is already an occult strabismus, it is recommended to wear them for both distance and near. Patients with high astigmatism do not see clearly at distance or near and need to wear glasses often.
What are progressive multifocal lenses?
A: Progressive multifocal lenses, also known as PAL (ProgressiveAdditionalLens), are specially designed lenses with an optical area above the lens to see far, an optical area below to see near, and a gradual change in the middle to see the middle distance. For a small percentage (15%) of myopic children with internal obliquity and strong adjustment, progressive multifocal lenses are more comfortable and have a relatively slowing effect on the development of myopia in the long term. However, for the majority (85%) of children with emmetropia, progressive multifocal lenses are not very different from ordinary monovision lenses and may even aggravate the emmetropia. Therefore, the decision to fit progressive multifocal lenses should be made by the doctor after a thorough examination of the patient’s eye position, binocular balance, accommodation, and accommodation.
What types of contact lenses are available? What are the advantages of contact lenses? What is RGP?
A: There are two types of contact lenses: soft and rigid. Most adults wear soft contact lenses, which are made of soft material with high water content and large diameter. The advantages are obvious: they are comfortable to wear, convenient, and meet the needs of work, activities, and socializing. Optically speaking, corneal contact lenses can also eliminate the trigeminal effect, eliminate oblique astigmatism, and reduce binocular retinal aberration. However, it should be noted that soft lenses are prone to protein precipitation and bacterial growth on the surface, and long-term wearing of soft lenses with high water content can lead to dry eyes, and corneal neovascularization or macropapillary conjunctivitis due to hypoxia and allergy. Therefore, soft lenses are not recommended for long-term use and are generally not recommended for children.
Rigid gas permeable contact lenses, also known as RGP (RigidGasPermeableContactLens), are the healthiest type of rigid corneal contact lenses, which have the advantages of soft lenses, but also have the advantages of super high oxygen permeability, excellent optical properties, easy to clean and care, not easy to produce dry eyes, etc., and are not easy to occur the above-mentioned soft lens-related complications, and are suitable for refractive and correct patients to wear for a long time. The use of RGP has become more and more popular in various countries, especially in Japan and Singapore, where RGP has become the first choice for the treatment of myopia in children and adolescents, and its role in slowing down the progression of myopia, in addition to its basic function of correcting vision, has been recognized. Clinical work and scientific studies have proven that long-term RGP wear can relatively slow down the growth of myopia in children and adolescents whose myopia is increasing too rapidly. The reason for this may be that RGP improves the quality of retinal imaging, effectively protects the eye, and stops the further increase of the eye axis. Its only disadvantage is that it is not as comfortable as soft lenses when you first wear it, but you can get used to it if you stick to it for 1~2 weeks.
What are OK lenses and what are their advantages?
A: OK lenses, that is, keratomileusis, belong to a kind of RGP, divided into day-wear OK lenses and night-wear OK lenses, the domestic use of night-wear OK lenses, the design of OK lenses is different from ordinary contact lenses, the central zone of its curvature is flatter than the human cornea, after wearing can be made through the lens of the mechanical compression effect of the central zone of the cornea temporarily flattened, so that the whole eye refractive power temporarily decreased, to achieve The purpose of “correcting” myopia. It is important to know that this “correction” is temporary, and its effect usually lasts only 1~2 days, if not worn daily, the cornea will regain its own shape through its own elasticity, thus making myopia “rebound” and return to its original myopic state.
Studies have found that long-term wear of OK lenses can also effectively slow the progression of myopia. The OK prescription is very strict and requires slit lamp examination to exclude other eye diseases, corneal curvature, corneal topography, objective optometry and subjective optometry, and very close follow-up after fitting to observe After fitting, very close follow-up is required to observe the effect of fitting and the occurrence of any complications. Therefore, the fitting of OK lenses can only be done in regular medical units.
Who is not suitable to wear contact lenses?
A: When a large number of people, including myopes, talk about contact lenses (contact lenses), nine times out of ten they say, “Contact lenses are dangerous and easily inflamed,” even though they have never had any real experience with them. In fact, with proper fitting and care, corneal contact lenses are quite safe, but are contraindicated in a few patients: acute and chronic ocular surface inflammation, whether keratitis, conjunctivitis or blepharitis; dry eye symptoms; intolerance of corneal contact lenses; and lack of good compliance.
Can children wear contact lenses?
A: The first reaction most parents of myopic children have when they hear their doctor recommend RGP/OK lenses is, “Can children wear contact lenses?” The reason is simple: “Children’s corneas are not well developed” and “contact lenses are easily inflamed”, which sounds reasonable. In fact, at the age of 6, children’s corneas have developed to adult level, and the above-mentioned contraindications have been ruled out, so theoretically they can all receive corrective lenses. However, we do not recommend soft contact lenses for children because they are unhealthy in the long run. This is not the case with hard lenses, whose many advantages have been described in detail and have proven to be safe and effective for children. Many of the children who wear RGP in our clinics are proficient in taking off and putting on their own lenses, and have a shorter learning curve than adults, and are very skilled after a few practice sessions.
Parents are understandably concerned about their children’s ability to take care of themselves with RGPs. The youngest child in our center is 4 years old and the average age is 7-8 years old, but we recommend that children in the second grade and above wear RGPs. Because RGP lenses are small in diameter and easily lost, children too young lack sufficient self-management skills, and improper lens rinsing and rubbing can cause protein deposits to remain on the lens surface or damage the lenses by excessive force. Therefore, the fitting of RGP for children and adolescents requires parents to have a full understanding of it, rational requirements, and to understand the child’s self-management ability, and to be strictly fitted under the guidance and assistance of the doctor.
The role of genetic and environmental factors is immense, and no amount of eye drops or therapeutic lenses can replace scientific and reasonable eye habits.
So far, neither the National Myopia Prevention and Treatment Expert Steering Group nor the National Education Commission has ever supervised or recommended any kind of myopia prevention and treatment equipment.
Can myopia be operated?
Myopia (including the accompanying astigmatism and some farsightedness) can be improved through surgery. Generally, it can be considered in adulthood (18 years of age), when the myopia is relatively stable and there are no contraindications after examination. However, it is important to understand that surgery is not a treatment for myopia, but a correction of vision. The myopic nature of the eye remains unchanged after surgery, but the vision is improved, making life easier and vision clearer!
Who is suitable for myopia surgery and is there an age requirement?
Indications: Patients who are unwilling or unable to wear glasses, patients who cannot tolerate contact lenses, patients with special occupational needs, patients with no contraindications to surgery, and patients who meet the requirements for surgery can be considered.
The age of surgery is generally 18~55 years old, but for patients younger than 18 years old or older than 55 years old, it is not necessarily true, mainly because before the age of 18, the development of the eye has not yet stopped and the prescription is not yet stable, so it is not done, but for some patients such as severe refractive aberration, certain diseases need, cannot be fitted with glasses but need to improve vision, although the age is not yet, after a comprehensive assessment can be considered (For example, for patients with hyperopic amblyopia, the age can be relaxed because the treatment should be early and cannot be delayed). For patients over 55 years of age, cataracts may appear, leading to vision loss, and cataract surgery is needed to solve the problem.
What are the methods of myopia surgery and how to choose?
There are many surgical methods and types of surgery, and most patients can find the most suitable method.
Excimer laser surgery: It can be divided into LASIK, LASEK, femtosecond laser, etc. Generally, for myopia below 500 degrees, LASEK is the best choice (except for patients with scars), and LASIK is better for 600~1200 degrees (scar patients are generally not affected), but the corneal thickness is required to be normal, if the cornea is thin or has corneal abnormalities, crystal surgery can be chosen.
Crystal surgery: Patients with 1200~2000 degrees, or patients with thin corneas who wish to obtain ideal results although the degree is not high, can choose crystal surgery for the best results. There are two types of crystals, anterior chamber and posterior chamber, and currently the posterior chamber is safer and more effective.
What are the advantages of refractive lens surgery that excimer laser surgery does not have? Who is it suitable for?
Compared to excimer laser surgery it has the following main advantages.
1. The correction range is much higher than that of excimer laser surgery. Generally, laser has the best effect for myopia below 800 degrees; for myopia below 1200 degrees, if the corneal thickness is normal, it can be considered, but with the increase of degree, there will be a certain degree of regression; above 1200 degrees, not only the effect is not ideal, but also the risk increases. In contrast, crystal surgery can be done around 2000 degrees, regardless of the degree, are very stable, will not regress.
2, laser surgery needs to cut off part of the cornea, so after doing the surgery, the cornea will become thinner, and once the tissue is cut off, it cannot be returned. There is myopia again, whether it can be done a second time depends on the situation of the remaining corneal thickness. Crystal surgery is to implant a lens without removing any eye tissue. If necessary, the crystal can be removed, that is, it can be restored to its original state, and then other surgeries can be considered, which means it is a reversible surgery.
3. After laser surgery, some parameters of the eye change. When cataract surgery is needed in old age, you need to tell the doctor that you have had laser surgery before (it is better to provide pre-operative data), and you need to consider the deviation and make adjustments when calculating the IOL degree, otherwise errors may occur. The parameters of the eye remain unchanged in their original state after the lens surgery, so that future cataract surgery will not be affected and there is no error.
4.The recovery of crystal surgery is fast, and you can see normally the next day. The postoperative medication time is short, usually 2~3 weeks, which is more convenient.
5.The post-operative vision of crystal surgery patients is greatly enhanced, that is to say, the vision of most patients after laser surgery is generally just about the same as wearing glasses before surgery, but the vision of the vast majority of patients after crystal surgery is better than that of wearing glasses before surgery, and some of the enhancement is quite large, and the visual quality is better for highly myopic eyes.
6.Since crystal surgery is so good, why don’t we let everyone have crystal surgery?
A: First of all, the cost of crystal surgery is relatively high, about twice as much as laser surgery. For each myopic patient, a comprehensive assessment of the surgical effect, safety and economy is needed to decide which method is the best, not the more expensive!
7. What tests and preparations do I need to do if I want to have myopia surgery?
A: First, if you are wearing contact lenses, you need to stop wearing them for 1 week (soft) to 3 weeks (hard), then go to the hospital for a thorough examination (Monday to Friday, usually takes 1 to 2 hours, no examination on weekends), determine if you can have surgery, communicate with your doctor and determine the type and mode of surgery. Laser surgery is usually then scheduled, pre-operative medication and instructions are received, and surgery is awaited. In the case of crystal surgery, pre-operative iris laser perforation is also required, which requires an appointment (usually Wednesday afternoon). After completing the perforation and having the doctor confirm it, it takes 1 week (for regular degrees) to 3 weeks (for special degrees) to book the crystal, dispense pre-operative medication, and make an appointment for surgery.