Deterioration of vision overtakes a person at any age. Modern gadgets contribute to the development of eye diseases. Prevention helps keep people he althy. Determination of visual fields is an important study in the detection of eye diseases. Modern equipment allows for painless diagnosis.
What is the field of view
The space that is visible to the fixed eye is called the field of view. The depth of field of vision is determined by the work of the retina. With a normal indicator, a person can freely navigate in space. If the field is disturbed, the patient does not see what is happening near him, cannot quickly determine the distance, experiences dizziness and headaches.
Determination of visual fields is included in the list of frequent examinations by an ophthalmologist. When a decrease in the field is detected, the cause is sought. This may be a violation of the structure of the eye or the development of a functional disease. A decrease in indicators indicates a disruption in the functioning of the retina, central nervoussystem or visual analyzer.
How the field of view is determined
Determining the field of view in a person reveals narrowing or loss of individual boundaries. How narrowed the vision is calculated in degrees. If a scotoma (a blind area in the field of view) became the reason for the change in the boundaries, then its indicators are determined in degrees or linear values.
Field of view - all points in space that one eye sees, looking motionless forward. In this case, the eye sees only a focused point, the peripheral parts of the retina are responsible for everything else. In a place where there is no field of view, the retina that perceives light has a defect.
To determine the periphery in ophthalmology, devices called the perimeter are used. With their help, the doctor conducts an examination according to certain methods. Basic methods for determining visual fields:
- control;
- kinetic;
- static;
- with double frequency.
The ophthalmologist examines each eye separately. One eye should be closed with a shield, and the other should look at a certain point, informing the doctor about the appearance of a certain object in the field of view.
Control diagnostics
The control method for determining the field of view produces an error in the measurement, but can be used in any conditions. It is used under the condition that high accuracy of the data obtained is not needed or as a preliminary examination to prescribe more accurate diagnostic studies.
The patient and the doctor are located on eachagainst a friend at a distance of 50–70 cm. One eye of the subject is closed with a shield or palm, the second eye is fixed on the control point. The doctor moves an object in space, usually a pencil or pen. The object moves perpendicular to the visual line at a distance of approximately 30 cm. The analysis is carried out horizontally from the ear, behind the nose, and vertically.
This method is used in the diagnosis of children, because it does not require long-term attention. In children, the indicators are 10 ° less than in adults. It is recommended to determine the field of view in children not earlier than 4 months, until this time children do not have stable fixation. The child's gaze is kept on a bright object and oscillatory movements are made on the periphery. As soon as the child has shifted his gaze to a moving object, mark the field of view.
Kinetic perimetry
With the kinetic method, the perimeter for determining the field of view is examined in 8 meridians. The test object moves across the surface from the periphery to the center.
To obtain reliable results, you should not look away from the given point. The speed of movement of the test object is 2° per 1 second. If a person has reduced vision, then the study is carried out without glasses.
Manual or computerized perimetry is used in medical centers. In manual diagnostics, the Foerster perimeter is used, where white test objects move on a fixed arc.
Hemispherical perimeters are more convenient to use due to the brightness of the background, which increases the accuracy of diagnosis. Thus, the definition of visual fields occurs at different levels from its base. Kinetic perimetry is used to determine significant changes due to a detected disease. With the development of glaucoma, more accurate information is provided by the method of static perimetry.
Static method
Determination of the peripheral field of view by a static method, involves the detection of light sensitivity using flashing objects. The examination uses devices that allow you to work in semi-automatic mode.
Modern devices have 25-30 programs in their arsenal. You can set the size, brightness and sequence of dots. Using the method, a threshold and screening strategy is determined. In the first case, a long concentration of attention is required and more time is spent, but the accuracy of the result will be high. The screening test is less sensitive and reduces diagnostic time.
Perimeters are a hemisphere with programs for examining the central visual field, detecting glaucoma, determining peripheral vision, etc.
If necessary, use combined options. First, an approximate determination of the fields of view takes place, and then, in the areas of decline, parameters are detected with high accuracy. This approach allows you to reduce time and increase the reliability of the result.
Double Rate Diagnosis
In the double frequency method, the white and black bands viewed by the patient change at a high frequency. ATDepending on whether the patient sees or not, black stripes are diagnosed in some areas. The technique is effective for early detection of diseases of the optic nerve, retina and glaucoma.
To detect glaucoma by this method, 5 signs were selected, according to which the diagnosis is made. Determining the average sensitivity deficit is the main indicator of the survey. Thanks to this, it is possible to diagnose up to 96% of the development of the disease at an early stage.
Indications for the procedure
Perimetry is performed as prescribed by an ophthalmologist. The simplest control method is carried out by the doctor directly in the office based on the patient's complaints. If there are doubts about the decrease in visual fields or the diagnosis, then the patient is sent for further diagnostics.
Changes in visual fields occur for the following reasons:
- eye diseases, disruption of the optic nerves;
- retinal detachment;
- burn or eye injury;
- oncological neoplasms of the visual organ;
- retinal hemorrhage.
When passing the commission, some types of work may require perimetry. Thus, the attention of the employee and the ability to respond are tested. With the help of perimetry, hidden craniocerebral injuries, chronic hypertension, strokes and neuritis are revealed.
Contraindications for perimetry
There are practically no contraindications for determining visual fields. It is not carried out with the aggressive behavior of the patient or the presence of a mental disorder in the patient.
The doctor will refuse to diagnose a person under the influence of alcohol or drugs. Even with a small amount of alcohol-containing drinks, the results may be distorted, in which case the examination is contraindicated.
It is impossible to determine visual fields if a person is mentally retarded and cannot follow the doctor's instructions. In this case, alternative methods of examination should be carried out.
Transcript of results
The data obtained during the survey should be correctly interpreted. Perimetry data is recorded on a special form and compared with standard indicators. Situations indicating the presence of pathologies:
- In some segments of the visual field, a person does not see the object.
- Identification of cattle that interfere with full vision. Possible cause is disease of the optic nerve or retina.
- General narrowing of vision. Depending on the zone (central, spectral, bilateral), a diagnosis is made. As a rule, the functioning of the eyes is reduced due to mechanical damage.
During the diagnosis, factors that may affect the change in visual field should be considered:
- deep-set eyes;
- low eyebrows;
- high nose bridge;
- severe reduction in vision;
- eye inflammation;
- infectious diseases.
Ophthalmologist reveals the reason for which narrowedvision. If the cause lies in eye diseases, then he prescribes treatment or further diagnostics. In case of diseases of the nervous system, a neurologist should be observed.
