The eye is very complex. We have tried to summarize it as simply and concisely as possible for you.
The eyes work like a film camera: Just like a camera lens, the light falls through the individual components of the eye, through the cornea, anterior chamber, pupil, lens and vitreous body to the retina. The light is concentrated there and the images are created. The optic nerve transmits the impressions from the retina to the brain.
The cornea, called cornea in Latin, can be seen as the window of the eye. The light falls through them. It is primarily responsible for the refraction of light in the eye. (Refractive power +43 dpt) The aqueous humor, which is located behind the cornea, supports this.
The cornea consists of five layers, the epithelial layer, Bowman's membrane, the stroma, Descemet's membrane and the endothelial cell layer. These layers are supplied with nutrients and oxygen by the tear fluid, aqueous humor and the marginal loop network.
The dermis, in Latin sclera, is very strong and elastic at the same time. It ensures that the eye is protected from harmful influences and stabilizes the shape of the eye. It almost completely encloses our eyeball, leaving two gaps: at the back of the eye for the optic nerves and at the front for the cornea. The white part of the dermis visible from the front is covered with transparent conjunctiva.
The iris, also called the iris, is the color in our eye that circles around the pupil. Thus responsible for our eye color. Like an aperture, the iris works with your muscles and assists the pupil in controlling the incidence of light.
The opening of the iris is considered to be the pupil. It works with the iris to control the amount of light entering the eye. If it is very bright or you are being dazzled, the pupil becomes small in order to let in as little light as possible. Conversely, in the dark, the pupil becomes as large as possible to catch as much light as possible and give us a better view
It also depends on our state of mind: the pupil can dilate when we are excited, scared or very happy. Likewise with drug use.
Our eye lens bundles the light entering through the pupil so that a sharp image is created on the retina. It is also responsible for accommodation, the focus adjustment. With the help of the ciliary muscle, it focuses for us on objects that are close or far away. At a young age, our lens is still very elastic and focusing works without any problems. In the course of life, it becomes more and more rigid and immobile, which can be used to recognize presbyopia between the ages of 40 and 50 and we can see less and less well up close.
The vitreous body fills the inside of the eye between the lens and the retina and gives the eye the necessary stability. It consists of 98% water and 2% hyaluronic acid and collagen fibers. Thus forms a transparent, gel-like substance.
The retina, also called the retina in Latin, is a very light-sensitive layer at the back of the eye. In the optical part of the retina there are approx. 127 million light receptors, also called rods, which are responsible for converting the incident light into nerve impulses, process them and are then forwarded to the brain by the optic nerves. Put simply, the retina is a kind of projection surface/screen for depicting our surroundings. The cone receptors are responsible for color vision. When someone has color blindness, it is usually related to a lack of cones on the retina.
The yellow spot / pit of vision
The yellow spot, also called the macula, is located in the center of the retina next to the opening of the optic nerve. It gets its name from the yellow pigment lutein, which is particularly strongly stored there. A small depression in the center of the macula is called the fovea centralis. It is the place of sharpest vision because the light receptors are packed closer together here than anywhere else. In the best case, what we see is shown there.
the optic nerve
The optic nerve transmits the light impulses as information from the retina to the brain. It is a half centimeter thick bundle of nerve fibers. Its point of exit from the retina is the so-called papilla, also known as the blind spot. As the name suggests, we are blind at this point because we have no receptors at this location.
ciliary body and zonular fibers
The zonular fibers fix and connect the lens in the circular ciliary body. When we focus on distant objects, the ciliary muscle is relaxed and wide, the zonules pull on the edges of the lens, flattening it. When the ciliary muscle tightens, the ring of muscle tightens and the fibers relax. Now that the lens can follow its natural elasticity and form like a sphere, it is at its highest refractive power, just right for close-up vision. We also call this process accommodation.
The ciliary body is also responsible for producing aqueous humor, the fluid that fills the space between the lens and the cornea.
The choroid is the connection between the sclera and the retina. It is rich in blood vessels and supplies the outer layers of the retina with oxygen.
We hope we were able to give you a little insight into our eye and how it works. We will continue to publish new articles regarding the anatomy & health of the eye here. If you are interested, just drop by again ;)
Sincerely, your Nicole Diem team