The eye has a very complex structure. We have tried to summarize it for you as simply and concisely as possible.
The eyes work like a film camera: just like a camera lens, light passes through the individual components of the eye, through the cornea, anterior chamber, pupil, lens and vitreous body to the retina. This is where the light is focused and images are created. From the retina, the optic nerve transmits the impressions to the brain.
Cornea
The cornea, or cornea in Latin, can be seen as the window of the eye. Light enters through it. It is primarily responsible for the refraction of light in the eye. (refractive power +43 dpt) This is supported by the aqueous humor, which is located behind the cornea.
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 lacrimal fluid, aqueous humor and the marginal loop network.
Leather skin
The 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 surrounds our eyeball and leaves two gaps: at the back of the eye for the optic nerves and at the front for the cornea. The white part of the sclera, which is visible from the front, is covered with a transparent conjunctiva.
iris (iris)
The iris, also known as the iris, is the color in our eye that circles around the pupil. It is therefore responsible for the color of our eyes. The iris works like a diaphragm with its muscles and helps the pupil to control the incidence of light.
Pupil
The pupil is the opening of the iris. It works together with the iris to regulate the amount of light entering the eye. If it is very bright or you are dazzled, the pupil becomes small 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 better vision
It also depends on our state of mind: The pupil can dilate when we are excited, anxious or very happy. The same applies to drug use.
Lens
Our eye lens focuses the light entering through the pupil to create a sharp image on the retina. It is also responsible for accommodation, the adjustment of focus. 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. As we get older, it becomes increasingly rigid and inflexible, which is why presbyopia becomes apparent between 40 and 50 and we are less and less able to see close up.
The vitreous body
The vitreous body fills the inside of the eye between the lens and the retina and provides the eye with the necessary stability. It consists of 98% water and 2% hyaluronic acid and collagen fibers. It therefore forms a transparent, gel-like substance.
The retina
The retina is a very light-sensitive layer at the back of the eye. In the optical part of the retina there are approximately 127 million light receptors, also known as rods, which are responsible for converting the incoming light into nerve impulses, processing them and then transmitting them to the brain via the optic nerves. In simple terms, the retina is a kind of projection surface/ screen for imaging our surroundings. The cone receptors are responsible for color vision. If someone has poor color vision, this is usually due to a lack of cones on the retina.
The yellow spot / visual pit
The yellow spot, also known as the macula, is located in the center of the retina next to the junction of the optic nerve. It gets its name from the yellow pigment lutein, which is stored there in particularly large quantities. A small depression in the center of the macula is called the fovea centralis. It is the place of sharpest vision, as the light receptors are more densely packed here than anywhere else. In the best case, our vision is imaged 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 fibres. Its exit point from the retina is the so-called optic disc, 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 therefore wide, the zonular fibers pull on the edges of the lens and thus bring it into a flat shape. If the ciliary muscle tenses, the muscle ring becomes narrower and the fibers relax. Now the lens can follow its natural elasticity and form itself like a sphere, then it has its highest refractive power, just right for near vision. We also call this process accommodation.
The ciliary body is also responsible for the production of aqueous humor, the fluid that fills the space between the lens and the cornea.
The choroid
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 have been able to give you a little insight into our eye and how it works. We will continue to publish new articles on the anatomy and health of the eye. If you are interested, just drop by again ;)
Yours sincerely, Nicole Diem Team