Glaucoma Diagnostic Methods

It is very important early detection of glaucoma, as successful treatment is possible at the very beginning of the disease. Changes in the early stages of the disease can sometimes be difficult to distinguish from non-threatened options. When diagnosing glaucoma, a symptom complex of five leading symptoms is taken into account, such as:

1. difficulty and deterioration of the outflow of moisture;
2. instability of intraocular pressure (diurnal fluctuations in norm are no more than 5 mm Hg, they are detected during loading and unloading tests with the help of elastotonometry);
3. increased intraocular pressure;
4. glaucomatous excavation;
5. lowering of visual functions.

For a long time, a patient with glaucoma can not notice any changes from the side of vision, and at a primary examination by an ophthalmologist, already great changes are detected. And in rare cases, an acute attack of glaucoma causes the patient to go straight to the clinic when, with a sudden increase in intraocular pressure, headaches, nausea, vomiting, visual impairment, redness of the eyes,

It is recommended that every person undergo an examination with an ophthalmologist when there are visual problems or there are any symptoms from the eyes (pain inside or redness of the eyes, doubling). The first examination of an ophthalmologist is necessary at the age of 40, when, as a rule, most people have visual problems when reading and there is a need for glasses. If there are certain symptoms, or there are glaucoma patients in the family, and there are other risk factors outlined above, eye examinations should be performed earlier.

[1], [2], [3], [4], [5], [6]

Ophthalmological examination

Currently, there are all modern technologies that allow painless, safe methods to conduct an eye examination of the patient.

First, visual acuity, the level of necessary optical correction and the potential sensitivity of the eye with the help of tables and various objects are checked. V healthy people it is designated 1.0 (100%). If vision is impaired, you need to find the cause. With glaucoma, visual acuity can not suffer for a long time. But if the patient has glaucoma, there are other eye diseases (for example, cataracts), then vision is reduced.

After determining the visual acuity, a slit lamp is examined.

Slit lamp is a special ophthalmic microscope that is equipped with a light source. The slit lamp rotates in such a way that the eye and its internal areas can be viewed at different angles. Usually the light ray has a slit shape, so the eye can be viewed layer by layer, that is, in "optical sections". The ocular fundus and the posterior parts of the eye are examined on a slit lamp equipped with a strong convex lens. For examination of the posterior part of the eye, the pupil is dilated (a few drops of mydriatic are instilled in the eye). After 15-20 minutes, when the pupil is sufficiently expanded, an examination is performed.

Measurement of intraocular pressure - tonometry - is described in detail above. The normal level of true intraocular pressure varies from 9 to 21 mm Hg. Article, the standards for a 10-g Maklakov tonometer - from 17 to 26 mm Hg. With a mass of 5 g - from 11 to 21 mm Hg. Art.

After a steady increase in intraocular pressure, the disintegration of visual functions begins, but there may be glaucoma with normal or reduced pressure. Day of measurement of intraocular pressure, contactless devices are used, which use a jet of air, which makes the cornea flat. The optical sensor detects when and how quickly the cornea has changed the curvature to a predetermined degree. The machine then recalculates the amount of time required for flattening, in millimeters of mercury. This method does not require local anesthesia. However, this study is not so precise. If the data obtained by contactless means are questionable, then they must be cross-checked by a contact method of investigation.

Study of the angle of the front chamber

The angle of the anterior chamber is the narrowest part of the anterior chamber. The front wall of the anterior chamber angle is formed by the Schwalbet ring, the TA and the scleral spur, the posterior by the root of the iris, and the apex by the base of the ciliary crown. Wide angle (40-45 °) - all structures of the angle of the anterior chamber (IV) are visible, medium wide (25-35 °) - only part of the apex of the angle (III) is defined, narrow (15-20 °) - ciliary body and scleral spur not visible (II), slit-shaped (5-10 °) - only part of TA (I) is defined, closed - the structures of the angle of the anterior chamber are not visible (0).

The pigment is deposited in the corner of the anterior chamber during the decay of the cells of the pigment epithelium of the iris and the ciliary body.

The examination of the anterior chamber angle is called gonioscopy. Inspection of it is carried out at the elucidation of the causes of increased intraocular pressure or when there is a fear that the angle can close and cause an acute attack of glaucoma. Since the periphery of the cornea is opaque, the angle of the anterior chamber is seen during gonioscopy using a special gonioscopic lens in contact with the eye. After instillation of a local anesthetic, the gon and ocular lens is placed on the eye, a whole system of mirrors inside the gonioscopic lens is used for examination. With this technique, the angle of the camera is seen for the presence of a substance that should not be there (pigment, blood or cellular material), which is a sign of inflammation. Also it is necessary to check whether there are any adhesions on any part of the iris. When assessing the width of the angle, one can predict the threat of closing the angle and determine the presence of congenital anomalies within the anterior chamber angle.

Inspection of the optic nerve

The intraocular part of the optic nerve is called the head or disc, the nerve segment of 1-3 mm in length applies to it. The blood supply to the disc depends to a certain extent on the level of intraocular pressure. The disc of the optic nerve consists of axons of ganglionic cells of the retina, astroglia, vessels and connective tissue. The number of nerve fibers in the optic nerve varies from 700 000 to 1 200 000, with age it gradually decreases. The disc of the optic nerve is divided into four sections: superficial (retinal), prelaminar, laminar and retro laminar. In the laminar section, connective tissue is added to the nerve fibers and astroglia, from which the scleral plate of the sclera is formed, consisting of several perforated sheets of connective tissue. Separated by astroglial interlayers. Perforations form 200-400 tubules, through each of which a bundle of nerve fibers passes. With increasing intraocular pressure, the upper and lower segments of the trellis plate are more easily deformed, which are thinner, and the openings in them are wider.

The diameter of the optic disc is 1.2-2 mm, and its area is 1.1-3.4 mm ². The size of the optic disc depends on the size of the scleral canal. With myopia, the canal is wider, with a farsightedness, a narrower one. In the optic nerve disc, the neural (neuroretinal) ring and the central depression - physiological excavation, in which a fibro-glial cord is located containing central retinal vessels are distinguished.

The blood supply to the optic nerve disk is of a segmental nature, due to the existence of zones of separation of the vascular set. The blood supply of the prelaminar and laminar sections of the optic nerve disk is carried out from the branches of the posterior ciliary arteries short, and the regional section from the central retinal artery system. Dependence of blood flow from intraocular pressure in the retro-laminar section of the optic nerve disk is due to the existence of recurrent arterial branches extending from the intraocular portion of the optic nerve disk.

Inspection of the optic disc is the most important part in the diagnosis of glaucoma. First, the size of the optic disc is estimated - a large disc has a more physiological excavation than a small one, but this is not a sign of the disease. The form of excavation is estimated. According to its form, it is determined whether the excavation is congenital or whether it has developed as a result of a pathological process.

The atrophy around the optic nerve disc points to glaucoma, although it can be observed in other diseases and even in the norm.

Glaucomatous excavation, atrophy, develops as a result of increased long time intraocular pressure. The difficulty of the blood flow leads to the depression of the grating plate, the displacement and compression of the optic nerve fibers occur, the plasma current through the perineural spaces is disrupted, the chronic ischemia of the optic nerve develops, which leads to glial atrophy.

Glaucomatous excavation is vertical-oval, there is an inflection of vessels at the edge of the optic nerve disc, excavation expands in all directions, but still more in the lower or upper-temporal directions. The edges of the excavation can be steep, dug or flat (saucer-shaped excavation).

With glaucoma, these changes can be observed in dynamics.

In the initial stage, the vascular bundle shifts to the nasal side, then the optic nerve disc begins to atrophy, its color changes, and the number of vessels falling on the optic nerve disk decreases. A small hemorrhage in the neuroretinal ring of the optic nerve disc is almost always a sign of glaucoma. Hemorrhages on the disc are peculiar signs of developing glaucomatous lesions. Local narrowing of the vessels of the retina is another sign of glaucoma, but they can also be observed in other lesions of the disc. If the vessel sharply curves when crossing the edge of the excavation, it gives even more reason to suspect its glaucomatous nature.

Simultaneously with optic atrophy, visual functions are impaired. These disorders are initially transient, inconspicuous for the patient and slowly progressing, they are detected only after a loss of 30% or more of the nerve fibers in the optic nerve disk. Disturbance of visual functions is expressed in the change in the field of vision, in the tempo adaptation, in the increase in the threshold for the critical frequency of confluence of flickering, in diminishing vision, and in color perception.

The examination of the fields of vision is called perimetry, and the state of the entire field of vision or its central part is estimated within 25-30 of the fixation point of the eye. When examining the field of vision of a glaucomatous patient, the following changes are found:

1. an increase in the blind spot, the appearance of paracentral cattle in the zone located at 10-20 from the fixation point of the gaze. They can be transient. Measuring the boundaries of a blind spot is important for stress tests. On an empty stomach, measure the blind spot with a water-drinking sample: in the morning on an empty stomach, you should quickly drink 200 g of water, the examination should be performed in 30 minutes. If the blind spot increases by 5 arcs, the sample is considered positive;
2. the peripheral field of vision begins to suffer from the upper-quadrant quadrant;
3. The field of view is concentrically narrowed;
4. light perception with an incorrect projection of light;
5. the initial changes in the visual field are reversible.

The average duration of glaucoma is about 7 years (without treatment there are serious complications and blindness).