Perimetry( study of visual fields) - Causes, symptoms and treatment. MF.

Perimetry is a method for investigating the boundaries of visual fields with their projection onto a spherical surface. The field of vision is part of the space that the eye sees with a fixed fixation of the glance and a fixed head. If you fix an object with your eyes, then apart from a clear distinction of this object, you can see other objects located at different distances from it and falling within the field of view of a person. Thus, the eye is characterized by peripheral vision, which is less distinct than the central sight.

Perimetry can be kinetic and static. At a kinetic perimetry the moving object is used, thus the moment of its occurrence and disappearance is noted, and at static varies illumination of object in the same position.

With the help of this method of research, it is possible to judge the nature of the change in the field of vision, from which one can judge the localization of the pathological process. Changes in the field of vision will be different with lesions of the retina, optic nerve, visual pathways and visual centers of the brain. In addition to narrowing the boundaries of the field of view, there may be some regions falling out. Such a limited defect is called scotoma.

The static perimetry is carried out on modern automated perimeters. It allows you to assess the sensitivity of the retina. With this type of perimeter, the object does not move, but arises in different parts of the field of view, while its size and brightness change.

Indications for perimetry are:

1. Glaucoma.
2. Diseases of the optic nerve( neuritis, trauma, ischemia).
3. Retinal pathology( dystrophy, hemorrhage, radiation burn, detachment, swelling).
4. Hypertensive disease.
5. Tumors of the brain.
6. Craniocerebral injury.
7. Disorders of cerebral circulation.
8. Assessment of vision during preventive examinations.

Contraindications to perimetry:

1. Mental illness of the patient.
2. Alcohol or narcotic intoxication.

For carrying out the kinetic perimetry , a special device called a perimeter is necessary. Perimeters are desktop( arc), projection and computer. The study is carried out separately for each eye, with the second eye covered with a bandage. During the examination of the field of view on the perimeter, the patient sits down in front of the device so that it is convenient to place the chin on a special stand, the eye being examined must be exactly opposite to the point fixed by the view, which is located in the center of the perimeter. The patient should not look away from this point. In this case, the doctor is located on the side of the device and moves one of the objects in the direction to the center along the meridians every 150. The patient should note the moment when looking motionless at the fixation mark, he will see the appearance of the moving object, the doctor at the same time fixes the degrees at which the object was seenand notes them on a special scheme. The movement of the object must be continued directly to the fixation mark to ensure the preservation of vision throughout the meridian. Depending on the visual acuity, objects of different diameters are used. So, with a high visual acuity, an object with a diameter of 3 mm is used, with a low visual acuity of 5-10 mm. The study is conducted mainly on 8 meridians, but more accurate results can be obtained from a study of 12 meridians.

There is no light sensation on the periphery of the retina, the extreme periphery of it is perceived only by white light, and as you move toward the center there is a feeling of blue, yellow, red and green. In the central part of the retina all colors are different. Thus, the field of view of each eye on a white object is characterized by the following boundaries: outside( to the temple) - 900, upward to the outside - 700, upwards - 50-550, up to the inside - 600, inside( to the nose) - 550, down - 500, down - 65-700, downward - 900. Small fluctuations in the range of 5-100 are possible. Investigation of the fields of vision for other colors is also done, as for white, but with colored objects, while the patient should note not the moment when he noticed a moving object, but the moment when he can call it a color. Very often it happens that there is no change in the visual fields to white, while other colors can reveal a narrowing.

The doctor puts all results into a special form, on which the visual fields are normal for each eye. All the "dropped out" areas are shaded.

The scheme of normal visual field boundaries obtained with perimetry of the left eye using white and color test objects( the black line denotes the boundaries of the field of vision examined by the white test object, the blind spot is painted gray).

When carrying out computer perimetry , the patient also fixes his eyes on a certain label. At different points of the device, objects of different brightness begin to appear in a chaotic order with a varying speed. As soon as the patient notices such an object, he presses the special button of the device. The device gives the results of the examination, on the basis of which the doctor makes an accurate diagnosis.

Computer perimetry

The duration of the procedure depends on the device: from 5 minutes on the computer perimeter and up to 20 minutes on the arc and projection perimeters.

It should be remembered that the heavily hung eyebrows, deep-set eyeballs, the lower eyelid lowering, the high bridge of nose, the stimulus on the large vessel near the optic nerve disc, the poor correction of vision, the too low vision, and the interference from the eyeglass frame can mimic the field changesview.

This method does not have any complications.

Doctor ophthalmologist One-piece E.A.