Liu Ying
Myopia is a common vision problem, which usually starts from childhood and adolescence, and is manifested as blurred vision of distant objects. For a long time, glasses have been an important means of vision correction. Traditional myopia glasses and contact lenses provide clearer vision by adjusting the light entering the eyes, but this method is not enough to control the deepening of myopia. Now, defocus glasses have gradually become the "new star" of myopia prevention and control glasses. What is the principle of such glasses? Who is suitable for myopic defocusing technology?
"Defocus" technology can slow eye axis growth
When people look at objects, light is accurately focused on the fundus retina through the lens in the eye. The retina converts light signals into electrical signals, which are sent to the brain through the optic nerve, so that people can see images. However, in the case of myopia, because the length of the eye axis (that is, the distance between the corneal surface and the retinal surface) is too long or the lens focusing ability is too strong, the light has been focused before reaching the retina, and the objects in the distance will be blurred.
On the basis of traditional vision correction, defocus glasses add a special optical effect, namely "defocus". This design enables the central field of vision of the eye (the area directly seen by the eye) to obtain clear vision, and the peripheral field of vision of the eye (the area seen by the edge of the eye) to have a slight and controlled defocus, so that the peripheral light can also focus in front of the retina. Research shows that the adjustment of peripheral defocus can effectively slow down the development of myopia, because it changes the optical signals in the surrounding area of the fundus, which are considered to be the key to control the growth of the eye.
In short, defocusing glasses can slow down the growth of the eye axis and control myopia by adjusting the peripheral vision light to focus in front of the retina, giving the eyeball a biological signal growing to the front of the retina light focus.
Two types of glasses have defocus effect
At present, myopia glasses using defocus technology mainly include two categories: frame glasses and corneal contact lenses.
Defocusing frame glasses are also called defocusing glasses clinically. The brands on the market include ZEISS Paradise, HOYA New Lexue, and Isilo Interest Control. Its advantages are easy to wear, safe, and wide range of application, except for people with dominant strabismus.
The corneal contact lenses using defocus technology include hard corneal contact lenses (such as OK lenses, defocus RGP glasses) and soft corneal contact lenses (such as defocus flexible lenses). Among them, OK lenses are usually worn at night, exerting pressure on the cornea to temporarily change the shape of the cornea, so that the wearer can maintain good vision without wearing glasses in the daytime. The defocus RGP glasses are suitable for people with a high degree of astigmatism in the cornea. For example, people with astigmatism greater than 300 degrees cannot easily adapt to OK lenses to control myopia. This is a kind of corneal contact lens worn in the daytime. The defocusing lenses that are also worn in the daytime are relatively soft, similar to the "contact lenses" worn by adults, and have a high degree of comfort, which can be divided into daily, monthly, and annual.
These three kinds of contact lenses are suitable for children and adolescents with rapidly increasing myopia, but not for patients with long-term eye infection or allergy, severe dry eye, patients under 8 years of age, and patients with diabetes, heart disease, and systemic immune system related diseases.
What are the precautions for matching glasses
Before the defocus frame glasses are equipped, a comprehensive eye examination should be carried out, such as mydriasis optometry, fundus examination, axial measurement, eye position examination, etc., to comprehensively assess the health of the eyes and the degree of myopia. During wearing, pay close attention to the reaction, communicate with the ophthalmologist in time if any discomfort occurs, and judge whether adjustment is necessary. Generally, most people can adapt to new glasses within a few weeks, and then have their vision, eye axis and diopter checked every six months to monitor the progress of myopia and the adaptation of glasses.
As a means to control myopia, defocus frame glasses are very important to wear correctly. Doctors recommend wearing it for as long as possible during the day, especially when performing close vision activities such as reading, writing or using electronic devices. It is also recommended to continue wearing glasses during outdoor activities. When using defocus frame glasses, if the ocular axis or myopia degree still increases rapidly, it is necessary to use 0.01% atropine eye drops under the guidance of a doctor.
The requirements for wearing defocused corneal contact lenses are different. Take the OK lens, which is widely used at present, for example. Because the lens needs to contact the cornea, the hygiene of hands, environment and lenses is very important. First of all, it is necessary to use the care product correctly. When using hydrogen peroxide for disinfection and neutralization, operate according to the instructions to ensure that the hydrogen peroxide is completely neutralized before wearing, so as not to cause damage to the eyes. Secondly, be sure to thoroughly clean your hands before touching the OK mirror to avoid bringing bacteria into it and causing secondary pollution. In addition, since the protein, lipid and eye secretion in tears may deposit on the lens surface, the OK lens should be cleaned regularly to avoid surface dirt and protein precipitation affecting the use effect and eye health.
OK glasses are generally suitable for people aged 8-18 years old with myopia ranging from 100 degrees to 600 degrees. Different brands of OK glasses may adapt to different individual conditions, and professional advice from doctors is needed. Long term use of electronic products may aggravate eye fatigue and affect the effect of OK mirror, so the wearer should ensure adequate sleep and avoid staying up late, which is conducive to maintaining the eye shaping effect. Once the ocular axis or myopia degree increases rapidly, 0.01% atropine eye drops can also be used for combined treatment.
Don't relax in daily eye care
Even if they wear myopia correction glasses, children and adolescents cannot relax in their daily eye care. The most important thing is to avoid using your eyes too long in close proximity. The use time of a single electronic product should not exceed 15 minutes, and the cumulative time of each day should not exceed 1 hour. The central position of the electronic screen should be about 10 cm below the eye line of sight, and the viewing distance should be 4-6 times the length of the diagonal of the screen. After half an hour of use, it is recommended to take a break and look into the distance for 10 minutes.
When reading and writing, keep upright sitting posture, and achieve "three ones", that is, one foot, one fist, one inch, one foot away from the book, one foot away from the chest, one fist away from the desk, and one inch away from the pen tip. Adhere to the "20-20-20" principle, that is, take a 20 second rest when using your eyes at close range for 20 minutes, and look 20 feet or 6 meters away.
Outdoor sports and exposure to sunlight are the most economical and effective ways to prevent and control myopia. At the same time, eat more foods rich in vitamins, such as avocados, animal liver, milk and eggs, carrots, green peppers, cereals, beans, bananas, oranges, tomatoes, etc., and reduce the intake of foods with high sugar content, such as chocolate, drinks, cakes, etc. Adequate sleep is also important to produce melatonin and reduce fatigue.
(The author is the chief ophthalmologist of Miyun District Hospital)
Picture provided in this edition: Visual China
