Can the eye axis be shortened? Can myopia be reversed? They are all true! But...

As parents pay more and more attention to their children's eyes, the "eye axis" has become more and more popular. Many parents pay close attention to their children's "eye axis" just like they pay attention to their children's height, hoping that the eye axis will grow slower and slower, and it would be best if it can stop growing.

I often see this or that kind of "legend" in my circle of friends - after using some myopia treatment methods, the previously soaring eye axis not only did not grow longer, but also shortened significantly, and myopia was "cured" in this way. Although I am skeptical, sometimes I still hope that my child's eye axis can also be shortened, myopia can be cured, and he or she can stop wearing glasses.

So let's talk about today, can the eye axis really be shortened? How should we view the issue of eye axis shortening? First, let's give the conclusion:

Can the eye axis be shortened? Yes

Can the eye axis be shortened continuously and significantly? No

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When we talk about the eye axis,

What are we discussing?

Before discussing the changes in the axial length of the eye, it is necessary for us to take a look at what the axial length of the eye is and how it is measured.

I believe that parents and friends who have done their homework know that, to put it simply, the axial length of the eye is the anterior-posterior diameter of the eyeball.

When children are young, their eye axes are often shorter and their eyes tend to be farsighted. As they age, the eye axes gradually increase. As the eye axes increase, the degree of hyperopia gradually decreases and reaches emmetropia, that is, a state of neither myopia nor hyperopia. As the eye axes continue to grow, myopia begins to appear. The longer the eye axes grow, the higher the degree of myopia.

The above is the development process of most myopia. The change of eye axis also represents the change of eye degree to a certain extent . Therefore, it is understandable why so many parents are very concerned about the change of their children's eye axis.

However, some parents frequently take their children to measure their eye axis, even once every one or two months, and their emotions are also affected by the fluctuation of the eye axis. Is this necessary? Let's first take a look at how the eye axis is measured.

The posterior pole of our eyeball wall is divided into three layers. The outermost layer is the sclera, which is relatively tough; the innermost layer is the retina, which is used for light perception; the middle layer is the choroid, which is the vascular layer. The thickness of the retina and sclera is usually stable, while the choroid, as a highly vascularized structure, will undergo rapid and large changes in thickness when blood flow changes.

Normally, the thickness of the choroid below the fovea is 0.2mm~0.3mm (200μm~300μm). The choroidal thickness in the general population can fluctuate between 0.1mm~0.6mm, which has a certain correlation with age and varies greatly between individuals during the day and night. Under special circumstances (such as inflammation), the choroidal thickness can even reach 1mm.

Strictly speaking, the anteroposterior diameter of the eyeball refers to the distance from the outer layer of the eyeball wall - the cornea to the sclera, while the axial length is not completely equivalent to the anteroposterior diameter of the eyeball. Currently, the commonly used axial length measurement uses an optical method. The distance from the tear film to the retinal pigment epithelium when the visual axis is stably fixed is the axial length measurement value.

As mentioned earlier, there is a layer of choroid between the retina and the sclera. When the thickness of the choroid increases, it will push the retina forward and the measured value of the axial length will become smaller. The effect of choroid thickness on the measured value of the axial length cannot be ignored. Sometimes the anteroposterior diameter of the eyeball does not change significantly, but the choroid thickness changes slightly, and the measured value of the axial length will also change accordingly.

Therefore, if you measure the axial length frequently and the measured value is longer or shorter, it is possible that what has actually changed is not the axial length, but the choroidal thickness.

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What factors can affect

Changes in axial length?

The main factors include:

● Natural light;

● Visual environment, especially defocus-induced and regulated eye development;

● Choroidal blood flow.

I believe that everyone is already very clear about the impact of the first two factors on the anterior-posterior diameter of the eyeball (here refers to the true length of the eyeball from the cornea to the sclera, not the axial measurement).

If the time spent outdoors is short, the eyes receive less natural light , and the eyes are used for a long time and continuously at close range, this will promote the growth of the eye axis in the long run; increase the time spent outdoors under natural light and avoid using the eyes for a long time at close range, and the natural growth rate of the eye axis will slow down .

Current myopia prevention and control measures based on defocus theory, such as orthokeratology lenses, defocus frame lenses, and defocus soft lenses, also show a certain effect in controlling the rapid growth of the eye axis.

Regarding the third factor, current research is not very thorough. The choroid may play an important role in the blood supply, oxygen supply, and growth regulation of the sclera, but the causal relationship and specific regulatory mechanism between choroidal blood flow, choroidal thickness, and the occurrence and development of myopia are still unclear . Choroidal thickness and choroidal blood flow cannot be equated.

In other words, in the long run, it is still unclear whether increased choroidal blood flow will increase choroidal thickness, whether increased choroidal blood flow and thickness can slow the progression of myopia, and how to continuously increase choroidal blood flow under natural conditions.

What is certain is that in the short term, the choroidal blood flow increases, the choroidal thickness increases, and the axial length measurement value becomes smaller. Thickening the choroid (which can be understood as congestion) through photothermal effects or other unsustainable, unnatural mechanisms may indeed lead to a shortened axial length measurement value in the short term. However, in the long term, whether the effect can be maintained, whether the choroid can continue to become thicker and thicker, and whether a highly congested choroid will bring some adverse effects, is still unknown. We still need to refer to more clinical data to find the answer.

Can the eye axis be shortened? If so,

Can it be shortened sustainably and significantly?

In the short term, shortening of the eye axis may be due to changes in choroidal thickness; if it remains unchanged or shortens in the long term, then it is highly likely that the distance from the cornea to the sclera is truly controlled and shortened. This type of degree regression is relatively stable and natural, and is what we most want to see.

Unfortunately, this type of axial shortening is also the rarest in clinical practice. Currently, most children go to school during the day and do homework at night. In this mode of life and study, this situation is very rare.

Therefore, the axial length of the eye can be shortened, but it is almost (please note it is "almost", not "absolutely") impossible for the axial length of the eye to shorten continuously and significantly under healthy conditions .

How should we view

What about shortened eye axis?

After reading the above content, I hope everyone can look at the shortening of the eye axis with a normal mind , just like ophthalmologists.

We should play outdoors more often with our children, help them develop good close-up eye habits, ensure adequate sleep, a balanced diet, a positive attitude, and a happy mood, and use medical methods that have been proven effective and safe by evidence-based medicine . Then, controlling the eye axis will be the natural result of treating the eyes well and complying with the laws of body development.

If there is a significant shortening of the eye axis, then we must have done something right and life has rewarded us with an unexpected surprise.

If we deliberately pursue shortening of the eye axis, we may often fail to achieve it, or even lose it after achieving it, and ultimately we may end up with some small regrets in the best years of our children's lives.

Finally, I hope all children have bright eyes to discover the beauty in life.

References

[1]The influence of the choroid on the onset and development of myopia: from perspectives of choroidal thickness and blood flow. Acta Ophthalmol. 2021 Nov;99(7):730-738.

[2]Precision of a new ocular biometer in children and comparison with IOLMaster. Sci Rep. 2018 Jan 22;8(1):1304.

[3]Accuracy of biometry for intraocular lens implantation using the new partial coherence interferometer, AL-scan. Korean J Ophthalmol. 2014 Dec;28(6):444-50.

[4]Candidate pathways for retina to scleral signaling in refractive eye growth. Exp Eye Res. 2022 Jun;219:109071.

[5]Choroidal thickness and ocular growth in childhood. Surv Ophthalmol. 2021 Mar-Apr;66(2):261-275.

Planning and production

Source: Health Express (ID: D- HealthExpress)

Author: Chi Xinzhuo, an ophthalmologist, PhD, Tongji Medical College, Huazhong University of Science and Technology

Editor: Yinuo

Proofread by Xu Lailinlin

The cover image and the images in this article are from the copyright library

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