Investigation of the hemodynamics of the eye

The study of hemodynamics of the eye is important in the diagnosis of various local and general vascular pathological conditions. The following basic methods are used for the study: ophthalmodinamometry, ophthalmoplethysmography, ophthalmosfigmography, rheophthalmography, ultrasonic dopplerography.

Ophthalmodinamometry (tonoscopy)

This method allows you to determine the level of blood pressure in the central artery (CAC) and the central vein (CVC) of the retina with a special device - a spring ophthalmodinamometer. In practical terms, it is more important to measure systolic and diastolic pressure in the CAC and to calculate the relationship between these parameters and blood pressure in the brachial artery. The method is used to diagnose the cerebral form of hypertension, stenosis and thrombosis of the carotid arteries.

The study is based on the following principle: if the intraocular pressure is artificially raised and ophthalmoscopy is performed at the same time , a pulse in the CAC can initially be observed, which corresponds to the moment of intraocular and arterial pressure equalization (diastolic pressure phase). With further increase in intraocular pressure, the arterial pulse disappears (the phase of systolic pressure). Increases in intraocular pressure are achieved by pressing the device sensor on the anesthetized sclera of the patient. The instrument readings, expressed in grams, are then converted into millimeters of mercury by the Bajar-Majito nomograph. Normally systolic pressure in the orbit is 65-70 mm Hg. Diastolic 45-50 mm Hg. Art.

For the normal nutrition of the retina, a certain ratio between the value of blood pressure in its vessels and the level of intraocular pressure should be maintained.

Ophthalmoplethysmography

The method of recording and measuring the fluctuations in the volume of the eye arising in connection with cardiac contractions. The method is used to diagnose occlusion in the system of carotid arteries, assess the condition of the walls of intraocular vessels in glaucoma, atherosclerosis, hypertension.

Ophthalmosfigmography

The method of investigation, allowing to register and measure pulse fluctuations of intraocular pressure in the process of a four-minute tonography but Grant.

Rheophthalmography

Allows you to quantify changes in the volume velocity of blood flow in the eye tissues according to the index of their resistance (impedance) to the alternating electric current of high frequency: as the volume flow velocity increases, the impedance of tissues decreases. With the help of this method, it is possible to determine the dynamics of the pathological process in the vascular tract of the eye, the degree of effectiveness of therapeutic, laser and surgical treatment, and to study mechanisms of the development of diseases of the organ of vision.

Ultrasound dopplerography

It allows to determine the linear velocity and direction of the blood flow in the internal carotid and ophthalmic arteries. The method is used for diagnostic purposes in traumas and eye diseases caused by stenotic or occlusive processes in these arteries.

Transillumination and diaphanoscopy of the eyeball

Investigation of intraocular structures can be carried out, not only by sending a beam of light with an ophthalmoscope through the pupil, but also by directing light into the eye through the sclera -diax- scleral translucence (diaphanoscopy). The illumination of the eye through the cornea is called transillumination. These studies can be performed using diaphanoscopes operating from incandescent lamps or fiber optic fibers, which are preferred because they do not adversely affect the tissues of the eye.

The study is carried out after careful anesthesia of the eyeball in a well-darkened room. The attenuation or disappearance of the luminescence may be noted if there is a dense formation inside the eye (tumor) at the moment when the illuminator is above it, or with massive hemorrhage into the vitreous. On the site opposite the illuminated site of the sclera, in this study, one can see a shadow from a foreign body located near the wall, if it is not too small and keeps the light well.

With transillumination, it is possible to consider well the "girdle" of the ciliary body, as well as postconjunctive subconjunctival scleral ruptures.

Fluorescent retinal angiography

This method of investigating the retinal vessels is based on an objective recording of the passage of a 5-10% solution of the sodium salt of fluorescein through the blood stream by serial photography. The method is based on the ability of fluorescein to give a bright glow when irradiated with poly- or monochromatic light.

Fluorescence angiography can be performed only in the presence of transparent optical media of the eyeball. For the purpose of contrasting the retinal vessels, a sterile, pyrogen-free 5-10% solution of the sodium salt of fluorescein is injected into the ulnar vein. For the dynamic observation of the passage of fluorescein through the vessels of the retina, special instruments are used: retinophytes and fundus cameras of various models.

When the dye passes through the vessels of the retina, the following stages are distinguished: choroidal, arterial, early and late venous. Normally, the length of time from the introduction of the dye to its appearance in the arteries of the retina is 8-13 seconds.

The results of this study are very important in differential diagnosis in various diseases and injuries of the retina and optic nerve.

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

Echoophthalmography

Echo-ophthalmography is an ultrasound method for studying the structures of the eyeball used in ophthalmology for diagnostic purposes. The method is based on the principle of ultrasonic location, consisting in the ability of ultrasound to reflect from the interface of two media having different densities. The source and simultaneously the receiver of ultrasonic oscillations is a piezoelectric plate placed in a special probe, which is attached to the eyeball. The reflected and perceived echoes are reproduced on the screen of the electron-beam tube in the form of vertical pulses.

The method is used to measure normal anatomo-topographic relationships of intraocular structures, to diagnose various pathological conditions inside the eye: retinal detachment and vascular closure, tumors and foreign bodies. The value of ultrasound location especially increases in the presence of opacification of the optical media of the eye, when the application of basic methods of research - ophthalmoscopy and biomicroscopy - is impossible.

For the study, special instruments are used - echo-ophthalmoscopes, one of them working in one-dimensional A-mode (ECHO-21, EOM-24, etc.), and others - in two-dimensional B-mode.

When working in the A-mode (obtaining a one-dimensional image), it is possible to measure the anteroposterior axis of the eye and receive echoes from the normal structures of the eyeball, as well as to detect some pathological formations inside the eye (blood clots, foreign bodies, tumor).

Research in B-mode has a significant advantage, because it recreates a visual two-dimensional picture, that is, an image of the "cross-section" of the eyeball, which significantly improves the accuracy and informative nature of the study.

Entoptometry

Since the most commonly used methods in the clinical practice of assessing the state of the organ of vision (visometry, perimetry ) do not always provide an unmistakable and complete picture of the functional state of the retina and the entire visual analyzer, there is a need to use no more complex but more informative functional ophthalmological tests. These include entoptic phenomena (Greek ento - inside, orto - see). This term denotes the subjective visual sensations of the patient that arise as a result of exposure to the receptor field of the retina of adequate and inadequate stimuli, and they can have different nature: mechanical, electrical, light, etc.

Mechanophosphene - a phenomenon in the form of a glow in the eye when pressing on the eyeball. The study is carried out in a dark room, isolated from external sound and light stimuli, and pressure on the eye can be rendered both with the use of a glass eyeglass stick and by pressing a finger through the skin of the eyelid.

The pressure on the eyeball is carried out in four quadrants at a distance of 12-14 mm from the limb when the patient looks to the side opposite to the location of the quadrant in which the stimulation is performed. The results of the study are considered positive if the patient sees a dark spot with a bright glowing rim on the opposite side of the quadrant where the stimulation is performed. This indicates the preservation of retinal function in this quadrant.

[6]

Autophthalmoscopy

The method, allowing to assess the safety of the functional state of the central parts of the retina, even with opaque optical media of the eyeball. The results of the study are considered positive if, during rhythmic movements of the tip of the diaphanoscope on the surface of the sclera (after drop anesthesia), the patient observes the appearance of a pattern of "cobweb", "tree branches without leaves" or "cracked earth", which corresponds to the pattern of branching of the retinal vessels.

Light banded sample is designed to assess the functional retinal integrity in opaque optical media (opacity of the cornea, cataracts ). The study is carried out by illuminating the Madox cylinder with an ophthalmoscope attached to the examined eye of the patient. With functional preservation of the central parts of the retina, the examinee sees a strip of light directed perpendicular to the prism length of the Madox cylinder prisms, regardless of its orientation in space.