The eye is considered the most important sensory organ in humans. The eye enables optical perception, vision. This is done in cooperation with the brain – the eye receives light stimuli, which are processed brain for optical perception.
What is the eye?
A cross-section of the human eye showing its anatomical components. Click image to enlarge. To process light reflections into optical perception, humans have two eyes. These react to electromagnetic radiation, the light. Thus, the eyes together with the brain, enable the perception of colors. In addition to this task of allowing people to see colors, the nature of the eyes is also responsible for visual acuity. Since the eye is so important for humans, it is anatomically protected. The eye lies protected in the eye socket and for further protection from external influences in front of the eye is the eyelid with the eyelashes. This closes reflexively and if something, a speck of dust for example, does get into the eye, tear fluid is produced to flush out the foreign body. When looking into the sun, it is difficult not to blink, or rather, to keep the eyes open. This is also a protective mechanism of the eye.
Anatomy and structure
The anatomy of the eye is very complex, it consists of muscles, receptors, skin and nerves. The eye itself is the vitreous body, which is located behind the eyelashes. This is surrounded by the sclera and in front of the pupil it is detached from the cornea for a bit before continuing. Behind this is the pupil, surrounded by the colored iris, also called the iris. Behind the iris is the lens, it is embedded in the ciliary muscle. On the other side of the vitreous, sort of opposite the lens, is the retina, it runs roughly along the back half of the vitreous. In its center is the optic nerve, which carries stimuli from the eye to the brain.
Functions and tasks
The functioning of the eye proceeds with the help of receptors. Light enters the vitreous body through the pupil and cornea. The lens refracts the light rays from outside and transmits them to the retina. There sit the color receptors that process different hues and brightnesses. These are about a hundred million sensory cells that make their contribution to vision. They convert the incoming light rays and transmit the signals to the optic nerve. They are divided into rods and cones. While rods take care of brightness, cones are responsible for colors. They are divided into three types – red, blue, and green sensitive. Their information to the brain makes it possible to see color. So, when it is dark, a person does not see colors because these cones function only in good light conditions. The cones are more sensitive, they also work at night. The ciliary nerve is responsible for the focus of the lens. If it contracts, the lens focuses. If you look relaxed or sleep, then this muscle in the eye remains loose.
Diseases
In humans, there are a number of ailments and diseases that can occur in the eyes. Very common are various visual defects that can be corrected with glasses, contact lenses or even surgery. Nearsightedness, for example, causes things farther from the eye not to be seen sharply, but to become blurred. This can have various causes and is measured in diopters. The opposite of this is farsightedness. This is where you don’t see things that are close by as sharply as you should. Astigmatism is a curvature of the cornea that affects vision just as often. It can be combined with nearsightedness and farsightedness and causes distorted perception. Furthermore, there is color vision deficiency and color blindness, caused by a defect in the retina. This affects more men than women. There are two types. The lack of the ability to see colors at all and red-green vision deficiency. Called night blindness, it makes it difficult to see at night and at dusk.
Typical and common eye diseases
- Eye inflammation
- Eye pain
- Conjunctivitis
- Double vision (diplopia)
- Light sensitivity
