Why is everyone so focused on vision? Because vision refers to the ability of the retina to distinguish images, in the five senses of human vision, hearing, taste, smell and touch, vision acquires more information than the other four combined.

So, how do people use their eyes and brains to see? What is the development process of myopia? What should we do to protect vision?

From light to image

Eye + brain = vision

Using a magnifying glass to ignite small pieces of paper in the sun this small experiment, the principle is the convergence of the magnifying glass on the light - sunlight through the magnifying glass will converge to a small point, all the heat of the light will be gathered together, when the temperature reaches the ignition point, the paper will burn up.

In fact, everyone hides a pair of "magnifying glass" - eyes. In fact, the principle of our eyes and cameras is very similar, now please turn into a beam of light, using the camera as an analogy, and experience an eyeball journey.

First of all, the first level we enter is the cornea, commonly known as the "black eye", equivalent to the camera lens.

It occupies 1/6 of the surface area of the eye, is about 11.5 mm in diameter, 0.6 mm thick in the center, 1 mm thick on the side, and its refractive power is about 42D, where the light has begun to converge.

Next, passing by is the iris around the pupil, equivalent to the camera aperture, if the light is too strong too harsh, the pupil will shrink, and vice versa.

The third level is the important level "lens", equivalent to the camera's automatic zoom lens, behind the pupil iris. Normal visual acuity can see both near and far, all depends on the adjustment of the lens.

When looking far, the ciliary muscle relaxes, suspensory ligament tenses, lens becomes flattened and refractive power decreases. When looking closely, the ciliary muscle contracts, the suspensory ligament relaxes, the lens becomes convex depending on its own elasticity, and the refractive power increases.

However, if you stare at nearby objects for a long time, the lens will always be in a full state, and the convergence ability of light is always strong. In the long run, when we look at distant objects, the lens is difficult to restore to the flat state, so the light can only converge before the retina after passing through the lens, which is myopia.

If the lens is difficult to adjust from a flat state to a full state, then when looking at nearby objects, the light will converge behind the retina, which is hyperopia.

Like the above, light rays converge in one place through a series of convergent actions, and eventually hit the retina for light-sensitive effects, much like camera film. The most sensitive part of the retina is called the macula.

Although the retina is very thin, the structure is very complex, divided into 10 layers, light-sensitive cells are mainly cones and rods, cones are mainly responsible for bright vision and color vision, rods are mainly responsible for dark vision.

At this point, the visual image has not yet been produced, the journey has not yet reached the end, and we need our brain to enter the C position.

After receiving the light signal, the retina will do a very important thing - convert the light signal into a micro current signal. This signal contains the shape, size, color, etc., and is transmitted through the optic nerve to the visual center, that is, the visual cortex located in the back of the head, and then the brain will begin to study the color, shape, depth, and what the object is and so on.

Therefore, what we commonly call seeing objects "with our eyes" is actually the vision produced by the visual center of the brain. Without the brain constantly working as a visual information processor, the visual information received through the eyes would be a jumble.

From squarely to nearsightedness

Spasm + non-relaxation = imbalance

Now that we understand how the eyes and brain perceive images, let's talk about myopia.

The development of the human eye actually begins with farsightedness. Newborns have small eyeballs and short eye axes, all of which are "farsighted".

With the growth and development, the physiological structure of the eye gradually mature, vision is gradually becoming normal, to experience the process of farsightedness, face, stop, if the brake is not the car, it will continue to overdevelop and form myopia.

Therefore, when the height grows the fastest, it is also the "critical period" of myopia prevention. In the middle school period, students began a lot of close reading, outdoor activities reduced, becoming the occurrence and development of myopia "disaster area". The severity of myopia is also gradual, roughly divided into the following three steps:

Initially, the eye has not appeared axial hyperelongation, but if the close eye for a long time, heavy load, resulting in continuous contraction of the ciliary muscle spasm, the lens can not relax, adjust the imbalance. Just like "spring", excessive use of the eye to make the ciliary muscle this "spring" too tight, "spring" elasticity will become worse, look far can not relax, is commonly known as false myopia.

Then, the eye grows axially, even when the ciliary muscle is fully relaxed, the light can still only focus in front of the retina, and the eye changes from false myopia to true myopia.

Further, axial growth intensifies, from myopia to high myopia. Because the axis of the eye grows too long, it can lead to thinning of the retina and choroid and fundus complications.

In terms of specific prevention and control actions, the most important point is to achieve early detection and early intervention. If you have symptoms such as squinting, frequent blinking, and eye rubbing, go to a regular medical institution in time to check your vision and optometry, from the age of three, before adulthood, it is recommended to check once every 3 to 6 months.

Once myopia is diagnosed, it is necessary to choose to wear the right glasses, because myopia is irreversible, just like growing taller will not become shorter, and the eye axis will become longer and will not be shortened.

In addition, some students are "false myopia", do not need to wear glasses. How do you tell the difference between true and false? The most effective method is to perform an optometry after ciliary muscle paralysis, which is called "mydriatic optometry".

Scientific research shows that it is best to go outdoors in the sun for 2 hours every day, which can effectively prevent the occurrence and development of myopia. Compared with outdoor activities, indoor activities do not play a significant role in preventing myopia in children.