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2023 Author: Alfred Shackley | [email protected]. Last modified: 2023-05-21 13:14
The angle of view, or field, is the amount of space that the eye can encompass in a fixed position. Due to the presence of the field of view, we are well oriented in space.
It is characterized by size and is measured in degrees.
If there are no deviations, the indicators will be as follows:
- On the outer border - 90;
- Internal - 55-60;
- Top - 50-55;
- Lower - 70.
Since all people do not have the same vision, average indicators are taken as a basis. They define the norm.
In turn, its indicators directly depend on:
- How the orbit of the eye is arranged;
- The shape and size of the upper and lower eyelids;
- Features of the structure of the human eyeball.
Since a person's vision is limited by the structure of the skull, the mobility of the eyes and their section, the indicators will differ slightly, but the deviations are insignificant. Most people have a horizontal field of view of 190 degrees. Just measuring the angle shows the presence or absence of deviations. If they are, there are probably problems with the nervous system or visual acuity.
For field tests, white is used because it shows the largest angle. This is due to the peculiarities of the psychological perception of color. After all, it is for the eye - this is certain information, each person has an individual reaction to a particular color scheme. For example, blue has a wider angle of view than red, while green is the smallest.
At the present stage, computer research or perimetry is used to measure the field of view.
Static - a person looks at a stationary object, only the lighting changes. It may seem more intense or weaker. Do not be afraid of this - this is how the eye works. Thus, the degree of sensitivity of the eye is measured, which indicates the presence or absence of a certain disease, for example, glaucoma.
Kinetic - allowing you to determine the very angle of view. The essence of the procedure is that the object moves along a certain trajectory, for example, in a circle, where the eye loses sight of it, they put a mark.
The computer itself determines when to put a point, because the lighting is bad, and a concentrated person's reactions are aggravated, and the machine records a change in reaction to the appearance and disappearance of an object. This is how the border is determined, then its indicators are checked against those that correspond to the norm. By deviations, diseases of the visual apparatus or the brain are determined.
Amsler test - designed to determine pathological changes in the fundus and retina. For this, the person is asked to focus on a specific image. The specificity of vision is such that, with deviations, not all of the object is visible. Where the borders are not clear or completely absent, they are marked in a special way. This fact will help determine changes in the retina of the eye. The test requires a little concentration, since it is difficult to fix the gaze on the object depicted on the grid.
Indications for the study
Computer diagnostics is used for:
- Regular medical professional examinations;
- Poor circulation in the brain;
- Head trauma;
- Oncology of the brain;
- Various deviations in the retina of the eye;
- Diseases of the optic nerve;
The way a computerized study is carried out, and especially its results, affect subsequent treatment or professional activity. If the profession requires a lot of concentration and visual acuity, these conclusions are very important.
Preparation of a computer study of the visual field
There is no special preparation for testing.
However, it is recommended to adhere to the following rules:
- Do not consume alcohol and drugs;
- Set aside for a while the intake of antipsychotic, antipsychotic drugs, antidepressants and tranquilizers, they can affect the accuracy of the diagnosis;
- If there are infectious diseases of the organs of vision or an inflammatory process, it is better to postpone the study to another time, after recovery;
- Before checking, it is imperative to tell the doctor about various diseases and pathologies that took place in childhood or shortly before computer perimetry, and also indicate hereditary factors for various eye diseases.
How is research done with a computer?
It is based on the following algorithm:
- The person is asked to sit down near a special machine;
- The chin is placed on a support that fixes the head in one position;
- In this case, you need to look, without looking up, into a special window at a certain point or mark;
- Later objects begin to appear. As soon as a person pays attention to an object that has appeared, he immediately presses a button, which is located in a convenient place, right under the subject's hand;
- At this time, the doctor records the button signals on the screen.
This is an example of kinetic diagnostics. A special machine automatically generates the results of the study, which are printed out and the doctor makes an accurate diagnosis based on the decoding.
When the computer returns the result, it schematically depicts two eyes and a drawing of an object. The object in the picture cannot be completely solid due to the fact that, according to the norm, all people have a so-called blind zone. Accordingly, it is shaded in gray. By its size and location, disorders associated with the corpus luteum are determined, or a condition is stated within the normal range.
A blind spot is also called a scotoma - this is a place where there is no reaction to light stimulation, it is located in the same place as the optic nerve. There is the concept of an angioscotome, that is, on the contrary, the determination of the presence of a corresponding reaction, which indicates the location of the retinal vessels.
Scotomas, in turn, are negative - when a person is unable to fix image failures on his own and positive - the subject is fully aware of where the picture disappears. And the last characteristic is absolute and relative. They differ in size and location. Only knowing special information about them, it is possible to determine an accurate diagnosis.
In addition, the computer determines the degree of narrowing of the field of view. She makes it clear whether there is a retinal disease - hemianopsia. It also has varieties - full partial and other subspecies that ophthalmologists know about. If detected, treatment will be prescribed.
The very procedure of computer diagnostics is safe, there can be no complications after it. However, there are some contraindications to this study. We are talking about alcohol and drug intoxication. In this state, a person develops photophobia, which greatly interferes with adequate test results. Also, mental illness, in which a fear of bright light or an inadequate response to changes in the intensity of light radiation, is also observed, will interfere with the correct diagnosis.
After diagnosis, in some cases, there may be some discomfort in the eyes. But there is no reason to be afraid of him, in a few minutes vision will completely return to normal. The research lasts, in total, about half an hour.
The presence of computer diagnostics of the visual field is a powerful breakthrough in the study of the characteristics of the human eye and diseases associated with changes in its structure. The advantages are that the research is carried out quickly and without negative consequences, while it is highly accurate.