Binocular vision - sight with two eyes, in which a single visual volumetric image is formed, obtained by merging the images from both eyes into one whole.
Binocular vision allows full perception of the surrounding reality, stereoscopic vision, that is, the ability to determine the distances between objects. Monocular vision (one-eye sight) can give an idea of the shape of the object, its height and width, but it will not allow to determine the mutual spatial arrangement of objects.
Binocular vision widens the field of vision, with it the perception of visual images becomes more clear, the visual acuity increases. This is an important visual function, in its absence, it is impossible to perform qualitative work of a surgeon, pilot, driver, etc.
In newborns there is no combined eye movement (appears in 2-3 weeks) and binocular vision. A 6-to-8-week-old baby is able to fix and follow the object with both eyes. A 3-to-4-month-old baby has a fairly stable binocular fixation. And by the half-year the fusion reflex is formed - the main mechanism of binocular vision is the ability to merge images from both retinas in the cerebral cortex into a single stereoscopic image.
Binocular vision by the 3rd - 4th years is considered to be formed, and it is finally established to 6-7 years. Precisely the preschool age is the most dangerous for the violation of binocular vision and the formation of such pathology as strabismus.
In order for binocular vision to take place, the following conditions are necessary:
- visual acuity is not lower than 03-04 for each eye;
- when looking into the distance the parallel position of the eyeballs;
- correct combined eye movements in the direction of the object;
- the corresponding convergence (convergence) when viewed near;
- ability to bifovealnoy fusion (fusii);
- transparency of optical media (lens, cornea, vitreous), no changes in the optic nerve, retina, higher sections of the visual analyzer, up to the cortex of the cerebral hemispheres.
How to check binocular vision
- Experience of Sokolov is that a tube is attached to the eye through which the subject is looking into the distance. By the end of the tube from the side of the open eye, he puts his palm. With normal binocular vision, due to the imposition of images, the impression is created that there is an opening in the center of the palm through which the picture is seen, actually viewed through the tube.
- Method of Kalfa defines binocular function using two spokes. The researcher holds the spoke in its outstretched hand in a horizontal position and tries to reach the tip of the other, which is in the vertical position, the spokes. With binocular vision, this is easily accomplished. If it is missing, a miss occurs.
- Reading with a pencil - in a few centimeters from the nose of the researcher, place a pencil covering some of the letters. In the presence of binocular vision, despite the obstacle, the imposition of images from two eyes allows reading without changing the position of the head. Letters, for one eye closed with a pencil, are visible to the other eye and vice versa.
- Four-point color test based on the principle of separation of the fields of vision of the left and right eye with the help of color filters. There are four luminous circles - two green, one red and one white. The color of the circles and eyeglasses that the researcher puts on is selected in such a way that one circle is visible to one eye, two circles to another, and a white circle is visible with both eyes. With binocular vision, the subject sees four circles, while at the same time five circles. With monocular vision, this depends on which eye is involved in the vision - two red or three green. Studies are conducted near (0.5 m) and from a distance (5 m).