Eyeball: Structure, Function & Diseases

To “guard something like the apple of one’s eye ” means that this something is very valuable for someone. Seeing belongs to the five senses of a human being. It is already present in the womb and unfortunately it diminishes with age.

What is an eyeball?

The larger part of the eyeball , called bulbus oculi in Latin, is located in the eye sockets and is protected by them. It owes its name to its apple-like shape. The anterior, flattened side is visible and widens towards the back. The optic nerve forms the stalk, which lies directly in the middle. By the coloring, specialists can recognize diseases from which the person suffers. Where the eyeball is normally white, yellowish discoloration is evidence of a disease of the liver or gall bladder. Bloody deposits, known as petechiae, also indicate damage to the liver. The examination of the eyeball is not only part of the normal examination procedure for orthodox physicians. Alternative medicine also uses it for diagnoses. Although the bulbus oculi is only 2.5 cm in diameter, it is one of the most important organs of the human body. Even irritations in the brain can be detected by looking at the eyeball.

Anatomy and structure

The eyeball is surrounded by a thick layer of fat and lies within the bony orbit. The eyelids provide a permanent supply of moisture. This not only moistens the eye, but also cleans it evenly. Closing the eyelids does not act exclusively in case of imminent danger. Drying of the eyes during sleep is also prevented. Eyelashes and eyebrows are additional mechanisms that catch foreign bodies and keep them away from the eye. Over the entire eyeball is a hard covering known as the sclera. In the anterior part, it encloses the transparent cornea, and in the posterior part, it provides optimal protection for the optic nerve. At the front edge lies the conjunctiva, which not only covers the sclera in the area of the palpebral fissure. It also extends a little way behind the eyelids. When the eyelids are closed, this creates a closed bag that protects the eyeball. The conjunctiva is continuously wetted with tear fluid. At the same time, the eyelids ensure the transport of this fluid to the posterior corner of the eye. Due to the high salt content of the tear fluid, all harmful bacteria are killed. The visible part of the eyeball encloses its most important component: the lens. It is avascular and consists of a solid nucleus and a corneal layer.

Function and tasks

The function of the eyeball includes different tasks. For example, the image-receiving part, or vision, takes place in the retina. It is a thin and very sensitive skin that lies directly on the wall of the eyeball. When looking at the back part, the fundus of the eye, a round and white colored spot is noticeable. Also noticeable are reddish strands that branch from here and disappear toward the inside of the head. This is the optic disc. It contains no light-sensitive sensory cells and is therefore known as the “blind spot“. At the back of the eyeball is the “yellow spot“. This is responsible for sharp vision. This is possible because the retina is very thin here and light rays can penetrate easily. These light receptors consist of two different cells. The rod-shaped ones are responsible for distinguishing between light and dark. Cones, on the other hand, ensure that color differences can be detected. Nerve cells, which are connected in series, ensure that the impulse is transmitted directly to the brain.

Diseases and ailments

The fact that with increasing age the eyesight decreases is probably known to everyone. For this, there are aids that make a visual impairment almost invisible. Contact lenses and glasses are offered in many variations and through them the deficit can be reduced to a minimum. But these aids are not the only ones that contribute to a normal life. A widespread disability is the “cataract“. In this case, the lens of the eye becomes cloudy and the affected person can only see blurred. The cause of the disease is related to age. Only very rarely does it occur in young people. An outpatient operation, performed under local anesthesia, can provide relief for patients suffering from “cataract“. This is also true if the diagnosis is “glaucoma“.Here the optic nerve is damaged and patients complain about the restriction in sharp vision. Glaucoma is often the cause. This presses on the inside of the eyeball. An improvement of vision is not possible despite surgery. However, the progression of the disease can be slowed down significantly. Macular degeneration primarily attacks the retina at the back of the eyeball. This is where the “yellow spot” is located and when this is damaged, vision loss occurs in the peripheral field of vision. The first symptoms are distorted or blurred images. As a result, both reading and recognizing people becomes increasingly difficult. Not only older people are affected. Young people can also be inherited with this disease. It is important to consult an ophthalmologist at the first sign of the disease. This is able to initiate a therapy. Even if this does not lead to a cure. The progression of the disability can at least be stopped.