How Do Our Eyes See?
80% of the information flow from the sensory organs that allow us to perceive our environment to our brain is through our eyes.
80% of the information flow from the sensory organs that allow us to perceive our environment to our brain is through our eyes. It happens through. Let's try to understand how we see with interesting information about our eyes that we may not know. Among our sense organs, vision is the one that gives us the most perfect feeling. An eye is approximately 22-25 mm in diameter and weighs 7 grams.
Our eyes are created in a very protected structure within a pyramid-shaped bone cage called the orbital cavity. Considering all the muscles in the body, the eye muscles are the most active and fastest. A blink occurs in 100 – 150 milliseconds and it is possible to blink 5 times in a second. We blink an average of 17 times per minute, 14,280 times per day and 5.2 million times per year.
Our eyes are the fastest sharpening lens in the world. While looking somewhere far away; When you look up close, it focuses itself on close vision in less than 1/6 of a second. At the same time, the pupil, which has a magnificent diaphragm, adapts to the light instantly by rapidly expanding and contracting.
Although the image is formed upside down on our retina, we see straight. Even though we have two eyes, the image we see is only one. In fact, the organ that performs the visual function is our brain. The eyes are just receivers that serve to transmit the image to the brain. The optic nerve consists of nerve cell extensions in the retina, and each optic nerve contains approximately 1.2 million nerve fibers.
Of the twelve nerve pairs in total, which come from our brain and control the work of our organs called cranial nerves, six are related to the eye. The nerve controls other senses and organ functions. Additionally, in terms of resolution, the human eye has a resolution of 576 megapixels.
The eye basically consists of 3 layers. The outermost white colored hard layer is called SCLERA, the vascular layer in the middle is called UVEA, and the innermost neural network layer is called RETINA.
Sclera;It is the white part surrounding the outside of the eye and is the eyeball. It ensures the integrity of the It is also the place where the eye muscles attach. At the very center, it forms the cornea, which is called the glass layer, which is completely devoid of vessels and where the light coming into the eye is refracted the most. In order for objects to be seen clearly, the cornea must always be transparent. If the transparency of the cornea is impaired, not enough light can enter the eye and vision becomes blurred. For the cornea to be transparent, it must not have even a single blood vessel in its structure. It contains nerve cells. With this feature, the cornea and lens are places in the human body where blood does not flow. The cornea receives oxygen directly from the air through tears and receives its nutrition from both the tears and the fluid behind it.
The choroid layer;is located under the hard layer and is the vascular layer, which is the part with abundant blood vessels. It takes part in the nutrition of the eye. Iris: It is the colored part that we see when we look directly at the eye. The black circle in the middle is the pupil with a gap. The iris, whose color varies from person to person, contains muscle fibers that help enlarge and contract the pupil. The task of adjusting the amount of light that will pass into the lens is the pupil, which is a muscular diaphragm. There are two types of muscle groups in the iris. The vertically placed muscle fibers contract and cause the pupil to expand, while the circularly placed muscle fibers cause the pupil to contract when they contract. Thus, it ensures that the appropriate amount of light enters the eye according to the conditions. If the iris had such a function, you could only see well in certain light. A slightly dimmer environment would become pitch black, and in a slightly brighter environment, your eyes would be completely dazzled. For a better vision, our pupil expands in the dark and contracts in the light.
Eye lens:The transparent part with a diameter of 1 cm located just behind the pupil is the lens. It is composed of protein fibers, does not contain vessels like the cornea, and has the ability to change shape. The fibers that suspend the lens from both sides manage the movement. When looked at close up, the muscles contract and the middle of the lens becomes curved and increases its refraction. When looked at far away, the muscles relax and the middle of the lens flattens, its refraction decreases and the light is refracted at the appropriate rate, thus causing the retina to shine. It focuses on.
Retina;The third, innermost and network-shaped layer of the eye is a light-sensitive layer. It is the part where light stimuli are received. Colored and colorless images are received by the retina and a neural stimulus is created. With these nerves, the image is sent to the brain and evaluated. The image can occur anywhere in the retina, but the clearest image occurs in the macula, called the macular dot.
Now, let's look at how vision occurs. Light is necessary for a person to see. The wavelength of visible light is approximately between 397 nm and 723 nm. During vision, light beams coming from any object pass through the cornea and pupil, then refract through the eye lens and reach the retina at the back of the eye. The eyes convert light energy in the visible spectrum into stimulation in the optic nerve. Rays hitting the retina produce potentials in light-sensitive vision cells called rods and cones. Each human eye has 6 million cones and 120 million rods. There are no bacillus cells in the macular degeneration.
The retina has a structure consisting of approximately 10 layers, and photoreceptor cells, which are the cells that enable vision, are located in the outermost part close to the choroid layer. The pigment epithelial layer that supports these cells contains a high amount of melanin, a black pigment that allows light to be absorbed and prevents reflection from the retina. The photoreceptor cell layer is rich in vitamin A. Light reaching these cells causes an impulse to occur in the nerve cell after a series of chemical reactions.
Impulses that start in the retina are transmitted to the visual center at the back of the brain through more than a million visual nerve fibers. The area where the optic nerve leaves the eye is called the optic disc, and there are no cone and rod cells here and it is called the blind spot. In addition, after leaving the relevant vessels in the brain in the arteries and veins that feed our retina, it enters our eye from the central part of the optic nerve and distributes to the retina. The occipital lobes, located in both hemispheres of the brain and located at the back of your head, analyze the electrical signals and a flat image is created. In the article you are reading now, it occurs in an area of a few cubic centimeters in the vast landscape.
During vision, we actually convert the rays coming into our eyes into electrical signals and see the effect of these signals on our brain. Seeing is actually watching the electrical signals in our brain. As a result, our eyes are our windows to the world and they are magnificently created.
May the light of your eyes never go out! Stay happy, peaceful and healthy.
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