The device of the human eye. Blind Spot

A blind spot is a region that is insensitive to light on the retina. This is quite normal for the eye of a healthy person. There is a blind spot due to the peculiar device of the eyeball. On this site, the nerve fibers go on top of the retina, they collect into the optic nerve, and the latter, in turn, passes through the retina to the other side. This area of the eye does not contain light receptors and, accordingly, does not perceive visual information.

This irrational structure of the eye has an explanation from the point of view of evolution. The cephalopods have no blind spots in their eyes. In octopuses, for example, nerve fibers are formed in the optic nerve from the other side of the retina. Some try to give this phenomenon a rational explanation and evaluate it from the point of view of natural "saving" of energy and a more rational use of the resource of photopigments.

Blind spots are present in each eye and have the property to be located symmetrically. The person practically does not notice their presence. In order to identify the blind spot of the eye, it is necessary to use a special test picture. In addition, the work of the brain makes it possible to correct the image perceived by the organs of vision, as a result, we see a holistic image of an object without interference and stains.

Thus, the devices of the eye and the peculiarities of the central nervous system allow a person to concentrate on the examination of the object that interested him. Whether interest is dictated by a vital necessity, or is caused by the exceptional beauty of the forms, in any case a healthy eye allows you to get all the necessary visual information.

If we consider in more detail the structure of the human eye, we can identify a small depression located in the center of the fundus, it is also called the central fossa. It is this place that is the center of the best perception of the "picture". Accordingly, the main line of sight is characterized by an axial orientation along the central fovea, the center of the lens and the object under consideration.

The area around the central fossa became the location of the yellow spot. This place is responsible for day vision and best color perception. Removal from the yellow spot leads to a reduction in the retina of the number of cones and an increase in the content of rods. It is the rods that are responsible for twilight vision and serve as a means for the best perception of forms. That's it near the yellow spot and there is a blind spot. As mentioned earlier, this site is free from cones, and from sticks. A glade for the nipple of the optic nerve does not see anything.

The device of the eye is extremely reasonable. This natural optical device has a high functionality and is capable of providing up to ninety percent of information entering the human brain.

In fact, the presence of a light spot is the only natural irrationality in the structure of the human eye, which is fully compensated by its multifunctionality. If the central fossa and the yellow spot are responsible for the sharpness of the image and the best perception of light, then the peripheral part of the field, so-called clear vision, is given the function of creating the background and ensuring the central role of the center. Then follows a more distant periphery, it is responsible for the overall perception and has an increased sensitivity to motion signals. And the farthest periphery, which does not even receive the rays of light, creates a basic zero-color. It is the starting point for comparing color sensations.

The first blind spot in 1668 was described by Mariott Edm. For the King of France, Louis XIV, this discovery was a kind of entertainment. He felt unhealthy pleasure, considering his subjects as if they were without heads. Not even in modern literature, without using the image of this physiological feature of the structure of the human eye. The book "Stalker. Blind spot "by Viktor Nochkin is a vivid example.