Dorothy FarrarEyeball
The spherical eyeball , also called bulbus oculi, sits in the eye sockets and has a diameter of about 2.5 centimeters. Of all the senses, seeing is the most complex process. This is also reflected in the structure of the eyeball.
Definition
The largest part of the eyeball is not visible and is well protected in the eye socket. Macroscopically, the eyeball appears as a white sphere. The iris and pupil are clearly visible. Roughly speaking, the eyeball consists of three layers. In its core, three media are connected in series: the aqueous humour, the lens and the vitreous body.
Anatomy
The outer layer of the eyeball is called the tunica externa. It consists of the rear dermis (sclera) and the front cornea (cornea). The dermis is an opaque, stretch-resistant and tough connective tissue capsule. It ensures that the bulb retains its spherical shape.
In its front section, the dermis is covered by conjunctiva (conjunctiva). The cornea, on the other hand, is not covered by conjunctiva. In contrast to the dermis, the cornea is transparent. Their consistency is also coarse. In healthy people, the cornea is avascular, which means that it is nourished solely by aqueous humor, tear fluid and the arterial vessels that run along the edge of the cornea.
Schlemm’s canal, also known as Schlemm’s canal, runs at the transition from the sclera to the cornea. This is a ring-shaped blood vessel. Schlemm’s canal allows the drainage of the aqueous humor, which is formed on the so-called ciliary processes and fills the anterior and posterior chambers of the eye. If the aqueous humor cannot drain properly, for example because Schlemm’s canal is narrowed, the intraocular pressure increases.
The middle part of the middle eye skin (tunica media), the choroid (chorioidea) is attached to the sclera. The ciliary muscle (corpus ciliare) follows, which regulates the size of the eye lens. As just mentioned, the aqueous humor is formed on the connective tissue processes of the ciliary body.
At the base of the corpus ciliare is the iris, which is known as the iris. The iris contains pigment cells that can contain melanin. These cells are responsible for eye color. The pupil is in the middle of the iris. Depending on the incidence of light, their size is changed by the muscles of the iris.
The inner skin of the eye is the retina. It consists of a front light-insensitive and a rear light-sensitive section. The retina contains photoreceptors, the actual sensory cells of the eye. The photoreceptors can be divided into rods and cones. The rods are more responsible for distinguishing between light and dark, while the cones are color-sensitive.
Most sensory cells are found in the so-called yellow spot (macula lutea), the place of sharpest vision. On the other hand, there are hardly any sensory cells at the exit point of the optic nerve (optic nerve). This spot is therefore also known as the blind spot. The eyeball is moved by six muscles, which are controlled by three cranial nerves.
Function
During the visual process, the eye perceives different reflections of light in the environment.
The reflected light shines through the cornea, the lens of the eye and the vitreous body and finally falls on the retina. The light is bundled by the cornea and the lens. The amount of incident light is regulated by the pupil size.
The image is focused by the lens, which is adjusted using the ciliary muscles. The image projected onto the retina is processed in many receptors and converted into electrical impulses that are picked up by the nervous system.
The optic nerve transmits the image information to the brain. The processing of the impulses takes place in the visual cortex in the brain. This is located in the back of the head. However, other areas of the brain are also involved in the evaluation of the electrical impulses.
Content-related interpretations of what has been seen are then also made in the brain. Another task of the brain is to rotate the image of the retinal image. The image created on the retina is initially upside down.
Diseases
The most well-known aberrations of the eye are short-sightedness (myopia) and long-sightedness (hyperopia). In short-sightedness, the eyeball is too long; in long-sightedness, it is too short. The result is a blurred image in the distance or near.
If the lens of the eye is clouded, one speaks of a cataract or a cataract. The disease manifests itself in increasing visual impairment. Older people are mostly affected.
Glaucoma, on the other hand, can also occur in younger people. Glaucoma is an abnormal increase in intraocular pressure. The increase in pressure is caused by an obstruction in the outflow of aqueous humor. The consequences are diminishing visual impairment and one-sided headaches. In an acute glaucoma attack, the pressure increases very quickly and there is a risk of blindness.
There is also a risk of going blind with retinal detachment. Flashes of light and blurred or distorted vision are alarm symptoms and should be clarified immediately by the ophthalmologist.
Hello and welcome to my Health Guide & Encyclopedia! My name is Dorothy Farrar, and I'm the founder and main author of this platform.
My passion for health and wellness started at a young age when I became interested in the connection between the food we eat and the way we feel. This fascination led me to study nutrition and dietetics in college, where I learned about the importance of a balanced diet and the impact of various nutrients on the body.