How to choose children's corrective glasses? How to wear them?

Not long after the start of school, there seemed to be a few more students wearing glasses in the class. If teenagers become myopic and do not wear glasses, the brain will use compensation mechanisms such as eye adjustment, squinting and tilting the head to improve this condition, which will cause visual fatigue and visual dysfunction, resulting in a worsening of myopia.

Image source: soogif

So how do we choose the right glasses for our children? How do we wear them correctly? How do corrective lenses control the increase in the degree of correction? Let me answer these questions one by one.

01 How do children’s corrective lenses correct vision?

Because the eye axis of myopia becomes longer, the focus does not fall on the retina but in front of the retina, so a concave lens is used to make the central area of ​​the external light focus on the retina.

People with hyperopia usually have a shorter eye axis, and the focus of external light entering the eye falls on the back of the eyeball. Therefore, a convex lens is needed to correct it so that the light is focused on the retina so that people can see things clearly.

Usually, ordinary lenses have only one focus, and their main function is to help children see distant objects clearly. When using ordinary lenses to correct vision, the imaging design of the optical zone of the lens is completed on a plane, and the clearest correction is made for central vision.

However, the human retina is curved, so the peripheral images are formed on the back of the retina, forming a hyperopic defocus, which causes the eyeball to grow toward the image, so it has no effect on controlling myopia. (Defocus means that the image focus does not fall on the retina.)

Children's corrective lenses use "myopia peripheral defocus" technology. After wearing the defocus lenses, you can see things clearly (the central light is imaged at the center of the retina), but the periphery will be slightly blurry (the peripheral light is imaged in front of the retina).

Source: Pixabay

What is the significance of this? The human retina tends to move closer to the clear area. The peripheral defocus makes the peripheral light image in front of the retina, and the retina tends to move forward. This can prevent the eye axis from lengthening or lengthen more slowly, that is, prevent myopia from getting worse or worsen more slowly.

02 How to wear children’s corrective glasses correctly?

When wearing glasses for the first time, try to ensure that the eyeball sees things through the center of the lens. It is recommended to wear glasses for no less than 12 hours a day. It is also recommended to wear them all the time and not take them off from time to time, which will affect the myopia correction effect. According to clinical experimental results, the longer you wear the glasses, the better the effect will be.

Regardless of the brand of defocus lenses, they must be corrected according to the specific degree of comprehensive optometry. They cannot be under-corrected or over-corrected. In this case, the correction effect is relatively the best.

Corrective glasses require regular checkups, first one month at the beginning and then every three months thereafter. The main checks are on refractive power, eye axis, visual function, as well as lens wear and frame deformation.

03 How to choose suitable lenses and frames?

Normally, we may encounter this situation: there is no problem with the way we wear glasses, the processing degree of the lenses, the quality of the lenses, etc., but we always feel that the clarity is poor, we are uncomfortable wearing, the fatigue is aggravated, and even double vision, dizziness, etc., then we should consider the following aspects:

●The lens frame is too large;

● The pupil distance and pupil height are wrong;

● The nose pad is too short and the lens distance is too small;

● High and low ears, etc.;

● The temples are too long or the frames cannot sit flat on the ears.

The choice of frames and lenses is particularly important for a pair of frames that are comfortable to wear and can control myopia well. If the frame is too large, it may look fashionable and good, but the visual center of the eye is not at the optical center, and the correction effect of the lens is poor, which will lead to problems such as myopia deepening and eye fatigue. The wrong pupil distance and pupil height can also lead to the same visual problems.

Image source: provided by the author

In addition, there are a few points worth noting:

① Generally speaking, anyone who can wear single-vision lenses can wear defocus lenses. However, considering the special design of the lenses, there will be a certain impact on the image contrast. Therefore, it is recommended that people with strabismus or poor vision correction should be carefully fitted.

②The best wearing age is for children over 6 years old, and the refractive power should be greater than 50 degrees (including 50 degrees).

③When wearing such functional lenses, you should also pay attention to the selection of frames. The size should be determined according to the child's face shape, pupil distance, eccentricity and on-site trial wearing. It is recommended that the frame height is ≥30mm, ≮28mm. The upper edge of the frame should not exceed the eyebrows, the width should not exceed the cheekbones, and the eyelashes should not touch the lenses, that is, our black eyes are in the middle of the lenses. The eccentricity of both eyes should not exceed 10mm, preferably within 6mm, and 0-3mm is the best. When choosing a frame, a narrower nose bridge will be more stable and can retain more inner defocus areas. At the same time, you should choose an adjustable frame, and the material should not be easily deformed, that is, it should be stable and adjustable.

The above lenses with different design principles have achieved different degrees of myopia correction in clinical practice, but the correction effects vary due to differences in lens defocus and design. The specific lens suitable for a child should be considered comprehensively based on factors such as eye position, refractive power, and age.

In addition, the causes of myopia are complex, and preventive lenses are not 100% effective in preventing myopia from increasing in degree. After wearing glasses, you still need to supervise your child's eye habits and writing posture, and ensure your child's diet, work and rest schedule, and outdoor exercise, etc.

Source: Chongqing Science and Technology Museum

Author: Yu Jinlin, optometrist at Wodi Ophthalmology. Xu Xuan, associate chief physician, associate professor, former deputy director of ophthalmology at Daping Hospital.

Review experts: Huang He, Li Chunli, Xu Xiaoping

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