The Human eye

Brown, blue and green, these are the most common colors of our eyes. Besides them, there is a variety of other colors that are a combination of colors mentioned above. Many people are born with nondescript gray eyes that change into blue or brown color during the development. What do we really know about eye color, in fact?

The iris is the most forwardly protuberant part of the middle layer of the eye wall. It has a shape of annulus with a centrally located hole called a pupil. The outer edge of the iris changes into an algoid corpuscle. The inner edge sets bounds to a circular hole of a pupil. Pupil is not exactly centrally located, but it is shifted slightly medially. It partially separates the front and the rear chamber of the eyeball.

The sight is our most important sense, which we receive up to 80% of information from the extermal environment through. The humam eye is the organ, which provides the vision itself. It is a very complex and perfect system consisting of many parts that have to cooperate perfectly. The particular parts of the eye are the cornea, conjuctiva, sclera, lens, vitreous body, irides, retina and many others that will be discussed briefly in the following lines.

One of the basic conditions of normal eye function is good wetting of the surface of the eye with tears. There is not even in the accumulation of the tears or tears running down their face. Tears can be simply defined as a fluid coming out of our eyes when we cry or when our eyes "cry" - such as irritation.

The eye cornea is the transparent front elastic and the mostly curved part of the exterior ligamentous layer of the human eye. It has the shape of horizontally placed convex and comprises 20% of the surface of the eyeball. It is colorless, completely transparent and avascular. Together with the conjunctiva, sclera and tear film it represents a mechanical and chemically impermeable barrier between interior and exterior environment. On the outside it borders with the air and on the inside it is in contact with the aqueous humour. Due to its refractive power the eye cornea is the most important part of the visual system and it is a critical factor as far as the quality of the vision is concerned.

Intraocular pressure (eye pressure) is a term which probably everyone of us heard before either when visiting a doctor, optometrist, human eye optics or somewhere else. However, many people do not know what this term includes, what its function is and why it is important. The importance of intraocular pressure could be compared to nowadays very much „promoted“ blood pressure which people are familiar with and they know that its increase or decrease can have unpleasant consequences. We could talk about intraocular pressure in a very similar way.

The human eye consists of a simple objective which has two parts. These are the cornea and the lens. The amount of light which enters the eye is controlled by the iris which is located between the cornea and the lens. The pupil is located in the middle of the iris and it dilates and contracts depending on the intensity of illumination and thereby regulates the amount of light which enters the human eye.

For a human being, sight is considered to be the most important sense of all. Through sense organ, which is represented by the eye, a human being perceives perfect visual images of surrounding world. This ability demands a close connection between the eye as a periphery sensor and cerebral cortex. A human being perceives approximately 80% of all information from his environment through sight.

The retina is the individual organ of sight and forms the internal layer of the human eye. It covers whole ventricular side of the eyeball right to the pupillary edge of the iris. It attaches to the middle layer of the eye wall through its external surface and the vitreous body attaches to its internal surface. The retina functions as the film in a camera. It catches the image and sends it to the visual centers of the brain through the optic nerve. We divide the retina into two structurally and functionally different sections. Posterior section, which is situated in the posterior part of the eyeball behind the level of the equator, is formed by the optic part of the retina, its part in front of the equator.

There is not too much discussion going on about the dark circles under the eyes and if there is a mention of it, it is mostly in connection with the tips how to perfectly hide them with the help of make-up. Generally, we are satisfied with the explanation that we did not sleep long enough and thus we erase the problem from the world. But we need to realize that the circles or swellings under the eyes can signalize also something more serious.

The sight is the most important sense out of all five because it enables us to receive the information from the environment. The ability of the human eye to receive inputs from the outside is enabled by light refracting areas and the retina. We can simply say that the rays reflected from the object, which we are looking at, have to pass through four light refracting areas, the cornea, the aqueous humour, the eye lens and the vitreous body which form the optical system of the eye and create a real diminished image at one point on the retina which we then perceive.

If your work includes sitting behind the computer for a long time, straining your eyes, you surely have experienced that after a certain time the pain in the eyes, head, neck and back begin. You are getting very tired and wish to be home as soon as possible. These eye strain symptoms are felt by many people who work long hours with the computer and strain their eyes.

Pain in the eyes (pain, which has not been caused by an injury) can be described as burning, pulsing, pressure or stinging feeling in the eye surrounding. You can also have a feeling of a foreign object in the eye. Pain in the eyes, even though it is not taken in very seriously, can be a significant symptom of something much more severe. This means, that if the eye pain keeps coming back or persists for a longer time, it would be useful to visit a physician.

One of the fundamental conditions for natural functioning of the human eye is an appropriate moistening of the eye surface by tears. It does not lead to the accumulation of tears or their flowing down the cheeks. We can simply define tears as the liquid which flows out of our eyes when we are crying or when our eyes “water” – for example when irritated. They are the liquid product of lacrimal and meibomian glands and conjunctival goblet cells. In the case of irritation of the anterior segment of the human eye or emotional excitement the production of tears increases by couple of times.