What are blind spots of the eyes: tests, functions and abnormalities. Blind spot - structure and functions

The eyeball is built in such a way that the optic nerve and retinal cells process, receive, and transmit information received from external environment. At the same time, in the area of ​​connection of the retina and optic nerve fibers of the latter penetrate outer surface retina. In this regard, this area is devoid of a photoreceptor layer, that is, it is not able to perceive or transmit light rays. This anatomical feature in the building visual analyzer noted physicist Marriott back in the 17th century. Due to its structural features, he called this area a blind spot. It was later found that this eye structure is characteristic of all chordates, including birds, fish and mammals.

Each human eye has its own blind spot, but due to binocular vision, both of these spots go unnoticed in most cases. Even with monocular vision, it is not easy to notice a blind spot, since brain tissue easily compensates for the lack of information. To make it more clear, you can run a test. A different pattern is used for each eye.

To perform the test correctly, you need to place the image in such a way that both crosses are at eye level, the monitor plane and the plane of the face must be parallel, and the distance between them is 20-25 cm, the center line (of the nose) should be located directly in the center between the crosses .

To test your left eye, you need to close your right eye and focus on the cross that is circled. After this, you should gradually move your face away from the screen until the adjacent cross (without a circle) disappears. This area is called the blind spot.

After this, you can carry out the same procedure for the second eye (you need to look at the picture with your right eye and close your left).

In healthy people, the blind spot is located symmetrically on the right and left, so the distance from the screen at which the cross without the circle disappears should be the same.

Contents of the article: classList.toggle()">toggle

A blind spot in the eye is an area on the surface of the retina that is unable to perceive light impulses. There is such an area in every eye. Its dimensions are, on average, about 2 millimeters. Immunity to light stimuli is due to the fact that the blind spot lacks photosensitive receptors - rods and cones.

Historical reference

This phenomenon was first described by E. Marriott in the middle of the 17th century. The scientist took two people, put them opposite each other and asked each to look with one eye at a point located on the side of the opponent’s head.

After some time, it seemed to the subject that the person standing opposite had no head. But in fact, she simply fell into a blind spot. It is noteworthy that participation in such an experience was a favorite pastime of the King of France, Louis XIV.

Human vision is binocular. This means that both eyes are involved in the process of viewing certain objects. It is thanks to this that the blind spot is invisible to a person, because it is “overlaid” by the vision of the second eye.

Thus, the brain compensates for the lack of visual information. But if the size of the blind spot of the eye increases, this can serve as an ominous signal indicating some kind of eye disease.

Blind Spot Test

To detect this interesting phenomenon, just pass the following test:

• Place the monitor screen at a distance of 20 centimeters from the eye, strictly perpendicular to the gaze (level the tilt of the monitor if necessary);
• The tip of the nose should be strictly at the level of the middle of the distance between the cross and zero;
• Close your left eye and look at the cross with your right;
• Then, without blinking or taking your eyes off, smoothly move away from the monitor;
• After a while you will find that the zero has disappeared. (usually this happens at a distance of 30-35 centimeters from the monitor)

It means that he got into an area that is not perceived by your eye.

The same must be repeated for the second eye., only now you need to fix your gaze on the zero.

Normally, the distance from which you stopped seeing the image should be the same for both eyes. If the distance varies greatly (20 centimeters or more), you should consult a doctor

And it corresponds to the area that does not contain photoreceptors. Due to this, the blind spot does not perceive light rays. The size of this formation is about 2 mm, and it is usually round in shape. This structure was discovered relatively recently (in 1668) by the French physicist Mariotte. In this regard, there is another name for the blind spot - Mariotte's spot.

Structure of the blind spot

The structure of the blind spot is not much different from the other area retina, however, there are no photoreceptors, which leads to a decrease in the number of layers.

There is a blind spot in both eyeballs, but thanks binocular vision, a person does not feel his presence. By superimposing images of objects on top of each other, they compensate for the absence of part of the image. Also in the central structures of the brain, a compensatory mechanism is implemented, which works even in conditions of monocular vision, that is, with one closed eye. Due to this mechanism, the blind spot also becomes invisible.

Physiological role of the blind spot

What the functions of the blind spot are is not completely clear, but it redistributes the visual load that goes to the receptors. The blind spot area is not capable of perceiving images.

Symptoms of a blind spot lesion

As the size of the blind spot increases, the visual field changes. These symptoms appear quite early, so effective treatment is possible.

Complicating the situation is the fact that the patient has early stages there is no pain, which more often than other symptoms forces a person to seek help. If the patient delays the consultation, it can be difficult to restore vision.

Diagnostic methods for blind spot lesions

For a diagnostic search, the size of the blind spot is assessed. A special test is suitable for this, in which you need to look alternately with one eye and then with the other at the screen. The last one shows a cross and a zero. The screen itself is placed 25 cm from the patient, and its midline should coincide with the center of the face (nose). If the screen is removed, the opposite element will disappear due to falling into the blind spot area.

Blind spot test

To pass the test, you need to position yourself so that the cross and circle are at eye level, your face is parallel to the monitor, the distance to the monitor is approximately 20-25 cm, the center of the face (nose line) should be in the middle between the figures.

Left eye test

Close your right eye. With your left eye, fix your gaze on the circle. Begin to gradually move your face away from the monitor, without letting go of the black circle. At a certain distance from the monitor, the cross will disappear - this will be a blind spot.

Right eye testing

Close your left eye. With your right eye, fix your gaze on the cross. Begin to gradually move your face away from the monitor, without letting go of the cross. At a certain distance from the monitor, the black circle will disappear - this will be a blind spot.

Blind spot diseases

Conditions that affect the blind spot include:

• Optic disc congestion;
• Arterial hypertension;
• Diabetic retinopathy.

I would like to remind you that the blind spot is part of the retina, which also lacks photoreceptors. Due to binocular vision and adaptive processes in the brain, the blind spot is normally not noticeable to humans.

" article. Of course, a blind spot has nothing to do with magic directly, however, there is something magical in the fact that it is still found in every person.

The blind spot test is designed to clearly demonstrate the blind spot. that not the entire retinal region of the human eye is sensitive to light. In fact only Seems that we see everything that comes into our field of vision, but in fact there is a “blind spot” in our eyes where visual perception is simply absent. This area has a special name - “blind spot”.

The presence of blind spots (they are present in both eyes, but in different people- in different metas) - this is a reality due to the structure of the eye. So, the eye sees because the “bottom” of the eye is covered with special light-sensitive cells (rods and cones, if anyone remembers from school). These sensory cells must somehow transmit a signal from the eye to the visual center in the brain. This occurs along a nerve fiber from the eye to the brain.

So, the blind spot is the place where this nerve fiber exits “to the surface” of the eye. And since there cannot be sensitive cells on the nerves, they are not there. And accordingly, the part of the eye where the nerve exits from the eye to the brain cannot perceive visual images.

The blind spot can be detected using simple test . This is done like this: close your right eye and with your left eye look at the right cross, which is circled. Keep your face and monitor horizontal. Without taking your eyes off the right cross, move your face closer (or further away) from the monitor and at the same time watch the left cross (without looking at it). At a certain point he will disappear. This means that the cross is in a blind spot.

To test the other eye, use an inverted pattern:

So, the blind spot test shows the presence of blind spots in the eyes!

Based on materials from http://wowfacts.net/test-na-slepoe-pyatno/

We know that the optic nerve is also involved in the direct reception, processing and transmission of information. But it turns out that the junction of the retina and the optic nerve is designed in such a way that the fibers of the optic nerve protrude onto the outer surface of the retina. And in this place of the retina there are no light-sensitive receptors. This discovery was made in the mid-17th century by a French physicist Marriott, he called the effect caused by such a structural feature, blind spot. Later it turned out that the blind spot area is inherent in all chordates (including all vertebrates, birds, fish).

Both human eyes have a blind spot area, however, due to binocular vision, the blind spot remains invisible. Even if you close one eye, it is not easy to see the blind spot. The brain compensates for the missing visual information, and the blind spot goes unnoticed. For clarity, it is worth conducting a test. We have presented you with two test pictures for each eye.

To pass the test, you need to position yourself so that the crosses are at the level of your eyes, your face and monitor are parallel, the distance from the monitor is 20-25 cm, and the line of your nose should pass exactly in the middle between the crosses.

Close your right eye. With your left eye, look at the cross in the circle. Without taking your eyes off the cross in the circle, gradually move your face away from the monitor. At a certain distance from the monitor, the cross without the circle will disappear. This is the blind spot.

Now close your left eye. With your right eye, look at the cross in the next picture. The rest is the same as for the left eye.

Normally, the location of blind spots in a person’s eyes is symmetrical, which means that the distance from the monitor when the cross disappears should be the same for both eyes.