Many parents are worried about their children's excessive indoor life, worried that their children's eyesight will be adversely affected. Some parents have asked if there are alternatives to simulating outdoor activities in indoor environments, and in principle, there are naturally available. While children are still encouraged to engage in outdoor activities, it is also a good choice to choose the right alternative in cases where outdoor activities are really not possible.
Let's take a look at the principle of eye imaging, due to the different distance of the eye, the location of the imaging point falling inside the eye is also different. The distance between the eyes is large, and the imaging point position falls in front of the retina; If the eye distance is small, the imaging point is located at the back of the retina.
Outdoor activities are actually the result of long-distance eye use, and the imaging point is located in front of the retina. At this time, the lens thinning action reduces the curvature of the lens, increases the focal length, and moves the imaging point back towards the retina. If the imaging point does not fall on the retina, the eye axis shortening action is triggered, and the retina moves forward to meet the imaging point. This is the process of seeing far and the principle that experts encourage outdoor activities, the most obvious feature of which is that the imaging point must fall in front of the retina.
When the eye axis is too long or the corneal curvature is too high, the imaging point position in front of the retina cannot be completely moved back to the retina, and the imaging will be blurred, which is the myopic eye state.
In addition to the distance factor can affect the position of the imaging point entering the eye, the only thing left is to change the angle of light entry through the lens to affect the position of the imaging point inside the eye. Myopic eyes can use a concave lens to increase the angle of the object's light into the eye, and then the refraction angle after passing through the lens will also increase, and the focal length will be extended to move the position of the imaging point back, assisting the eye to complete the imaging process. This is the principle of myopia, OK mirror, laser surgery and other programs to correct vision, which shows that the concave lens scheme has the effect of moving the imaging point position back.
As can be seen in the figure, the angle of light entering the eye normally from point A in the distance is assumed to be an angle of 20 degrees, and the concave lens has a light divergence effect, and the angle of light is changed to a b angle of 25 degrees after passing through the concave lens, and the b angle of 25 degrees corresponds to the near analog point after the distance is shortened. Therefore, the essence of the concave lens scheme is that the angle of light entering the object is increased, simulating the effect of shortening the distance, so it does not have any principle of prevention and control of myopia, and is limited to assisting eye imaging when rigid seeing needs are needed.
As the distance between the eyes continues to shorten, the position of the imaging point inside the eye is constantly moving back. When the eye is used closely, the position of the imaging point falls behind the retina, and the lens thickening action is required to increase the curvature of the lens, and the focal length is reduced when the curvature increases, and the imaging point is moved forward to the retina.
When the eye is too close, the single lens thickening adjustment does not move the imaging point forward to the retina, which triggers the eye axis elongation action and shortens the distance between the retina and the imaging point. Over time, with the growth and development of the eyes, the eye axis continues to substantially elongate to form myopia, which is the principle of eye axis elongation.
As mentioned earlier, the most obvious feature of the long-looking action in outdoor activities is that the imaging point position must fall in front of the retina, so we only need to let the imaging point position also fall in front of the retina when we use the eye at close range to generate a far-looking action. Contrary to the backward position of the imaging point of the concave lens scheme, the convex lens scheme has the effect of moving the imaging point position forward, which can move the imaging point position forward to the front of the retina, and then generate a far-looking action after eye recognition, thereby blocking the source of myopia.
As can be seen in the figure, the normal angle of light entering the eye at the near C point is assumed to be a angle of 30 degrees, and the convex lens has the role of light pooling, and the angle of light is changed to a b angle of 25 degrees after passing through the convex lens, and the b angle of 25 degrees corresponds to the distant analog point after the distance is increased. Therefore, the essence of the convex lens scheme is that the angle of light entering the object is reduced, which simulates the effect of increasing the distance, and is the closest scheme to the eye action of outdoor activities.
In summary, the essence of the backward position of the imaging point of the concave lens scheme is the shortening of the simulation distance, and the essence of the position of the imaging point of the convex lens scheme is the increase of the simulation distance. Using the convex lens scheme, although it is indoor life or close use of the eye, because the imaging point is changed and falls in front of the retina, it still makes the eye form a far-sighting action for outdoor activities, which has the effect of exercising to protect vision. This is an alternative to simulating outdoor activities when there is too much indoor life, and the principle of movement of the imaging point position also determines the uniqueness of this scheme.