Special cells in the retina evaluate whether we see an image in focus or not.
With myopia, or nearsightedness, light rays are focused not on the retina, but in front of it. Most often, the reason here is that the eyeball has grown too large, too long, so that the retina has “moved away” from the focal plane. Our eyes are actively growing while we are still children, and it is during childhood that myopia most often manifests itself when the mechanism that controls the growth of the eyeball for some reason does not work.
The retina of the eye is formed by several dozen types of cells, which are arranged in several layers. (Photo by ZEISS Microscopy / Flickr.com.) “Myopia cell” from a mouse retina. (Photo: Northwestern University.) ‹ › View full size
But how does this mechanism work? It is believed that the main role here belongs to the retina: after all, it is the retina that perceives the image, and when the eye optical system acquires optimal parameters, the retina inhibits eye growth. However, for a long time no one knew what exactly was happening here, what kind of cells were involved, etc.
In a paper in Current Biology, researchers from Northwestern University report that they have found cells in the retina that may directly influence eye size. As you know, the retina is extremely complex: it consists of ten different cellular layers, one of these layers is formed by the so-called ganglion cells, of which there are fifty varieties, each with its own function. They themselves do not perceive light, but collect nerve signals from the photoreceptor layer, from rods and cones; Some of the ganglion cells specialize in movement, some in color, etc.
However, some of them have a unique property: they work differently depending on whether the image is precisely in focus or not. The response time of these cells depended on how close the visible object was: they reacted to distant objects with a strong delay, but if the object was made closer, then their response time decreased, and they became most sensitive when the “picture” was exactly in the focal plane. Essentially, they respond to image contrast by being integrated into complex neural networks with other elements of the retina.
Of course, it remains to be seen how these cells control the growth of the eyeball and how they are related to the development of myopia. The authors of the work believe that the whole point here is in the peculiarities of artificial lighting, in the balance of light waves of different lengths, to which the cells react as if they were normal contrast, so that due to their hyperactivity, the eye grows longer than necessary – and therefore, Sitting at home as a child is how we develop myopia. However, no matter how plausible the hypotheses may be, they still need to be verified by additional experiments.