Mechanism of vision or as we see with the eyes

As we see with the eyes



When the rays of light reflected from an object enter the eye, they are refracted by the cornea, the outer lens of the eye and the lens, the inner lens, and also to some extent by an intraocular clear fluid. This refraction focuses the rays of light on the retina, a collection of photosensitive cells in the fundus, forming an inverted image.


Light, stimulating the retina, creates an impulse that passes through the optic nerve into the brain. Here impulses are collected and interpreted as moving colors, shadows and shapes.





The lens changes its shape, focusing on objects with different distances.


Keep this book at arm's length, close your left eye and stare at the cross with your right eye, slowly moving the book toward you. At some point the circle will disappear.


The retina contains two types of light-receptor cells that are classified according to shape.


The wands are sensitive to light of low intensity, providing sensitivity to black, white and gray colors and good night vision. They are insensitive to color. In the retina of each eye there are about 125 million rods, which allows us to judge their microscopic size. They contain a purple photosensitive pigment rhodopsin. The light striking the stick is absorbed by the photopigment, and a very fast chemical reaction occurs, during which the pigment is destroyed. It stimulates nerve impulses that are transmitted through the optic nerve to the brain. The occurring chemical reaction causes an increased transmission in the dark and lowered in the light.


As soon as an electrical impulse enters the brain, the enzymes cause the regeneration of rhodopsin. The eye thus functions as a film projector. He sends to the brain not a continuous moving picture, but an infinite series of "frames", 8 per second.


The cones (or cones) are shorter and almost as thick as the rods. There are about 7 million of them, and they are concentrated in the center of the retina and are activated by the light of higher levels, so that they give more accurate visual information than the sticks. Cones are sensitive to the color frequencies of light.


The mechanism for transmitting color information from cones to the brain is in many ways similar to the transfer mechanism from rods, with the difference that each cone absorbs light in different parts of the spectrum: some are more sensitive to longer waves of the red and yellow range, but also perceive light at other frequencies; cones of the second type absorb mainly shorter blue waves; the third type absorbs green light from the middle of the spectral range. The nature of the transmitted signal varies according to the wavelength and intensity of the light source, so our perception of color is based on the interpretation of signals that deliver different information from cones of all three types.


People with color vision defects have a reduced number of conic cells of one type. Such violations are usually congenital. The bad gene is transmitted by women, but the disease affects only men. Therefore, 99% of women and only 90% of men have normal color vision.


In general, men usually have less visual acuity than women, and for this reason women are traditionally accepted for jobs such as sorting colored lenses.