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What does pzo mean in ophthalmology? Examination of the visual center of the eye using ultrasound

Ultrasound and optical biometry of the eye is a common procedure in ophthalmology, which allows one to calculate the anatomical characteristics of the eye without surgical intervention. The procedure is used to diagnose a number of diseases from ordinary myopia (nearsightedness) to cataracts and post-operative diagnosis and often helps to save vision.

Depending on the type of waves used for measurements, biometrics is divided into ultrasonic and optical.

Why is biometrics needed?

  • Selection of individual contact lenses.
  • Control of progressive myopia.
  • Diagnostics:
    • keratoconus (thinning and deformation of the cornea);
    • postoperative keratectasia;
    • corneas after transplantation.

Since myopia progresses especially quickly in children, regardless of correction methods, a biometric examination of the eye allows us to identify any deviations from the norm in a timely manner and change treatment. Indications for biometrics are:


The procedure is prescribed to patients who exhibit pathologies such as corneal clouding.
  • rapid deterioration of vision;
  • clouding and deformation of the cornea;
  • double vision, distortion of the image;
  • heaviness when closing the eyelids;
  • headaches and eye fatigue.

Types of biometrics and its implementation

Ultrasound diagnostics

To calculate anatomical parameters using ultrasound, direct contact of the probe with the skin of the eyelids is required. The patient must lie still so that the waves pass properly and the picture is clear. To improve conductivity, gel is applied to the eyelids. Ultrasound biometry is an older diagnostic method. The advantage of the technique is the mobility of the equipment, which is especially important for patients unable to move.

Optical technology

The technique is significantly different, since it uses the principle of interferometry, that is, the measurement is carried out using separated beams of electromagnetic radiation. It does not require contact with the patient’s eye, and is also considered a more accurate diagnostic method than ultrasound. Some devices use infrared laser beams with a wavelength of 780 nm. The stratification of radiation between the light reflected in the tear film and the pigment epithelium on the retina is detected by a sensitive scanner.

The optical biometric method does not require effort or additional caution on the part of the doctor. Once the equipment is aligned with the eye, further measurements are taken automatically.


Optical eye biometry is a non-contact diagnostic method that eliminates the human factor.

The optical method is considered more progressive and simpler than ultrasound biometrics, due to the exclusion of the human factor. The technique is more comfortable, since the patient does not suffer inconvenience due to eye contact with the device. Some devices combine ultrasound biometry with optical biometry to achieve more accurate measurements, regardless of diagnosis.

Decoding indicators

After the scan, the doctor receives the following data:

  • the length of the eye and the anterior-posterior axis;
  • radius of curvature of the anterior surface of the cornea (keratometry);
  • anterior chamber depth;
  • corneal diameter;
  • calculation of the optical power of the intraocular lens (IOL);
  • thickness of the cornea (pachymetry), lens and retina;
  • distance between limbs;
  • changes in the optical axis;
  • pupil size (pupilometry).

Measurements of corneal thickness and radius of curvature are especially important, as they allow the diagnosis of keratoconus and keratoglobus - changes in the cornea that cause it to become cone-shaped or spherical. Biometrics makes it possible to calculate how the thickness differs in these diseases from the center to the periphery and prescribe the correct correction.

The procedure provides accurate indicators of the condition of the visual organs and helps to identify pathologies, such as myopia.

In a healthy person, the thickness of the cornea should range from 410 to 625 microns, with it being thicker at the bottom than at the top. Changes in thickness may indicate diseases of the corneal endothelium or other genetic pathologies of the eye. Typically, the depth of the anterior chamber with keratoglobus increases by several millimeters, but decoding data from modern devices gives an accuracy of up to 2 micrometers. With myopia, biometry diagnoses elongation of the sagittal axis of varying degrees.

At the ninth week of intrauterine development, the sagittal size is 1 mm; by 12 weeks it increases to an average of 5.1 mm.

The total length of the eye of a premature infant (25-37 weeks after conception) increases linearly from 12.6 to 16.2 mm. The measurement results from a more recent study are shown in the table below.

Newborn eye measurement results during ultrasound examination:
1. The average depth of the anterior chamber (including the cornea) is 2.6 mm (2.4-2.9 mm).
2. The average thickness of the lens is 3.6 mm (3.4-3.9 mm).
3. The average length of the vitreous body is 10.4 mm (8.9-11.2 mm).
4. The total length of the newborn's eye is 16.6 mm (15.3-17.6 mm).

Postnatal growth of the emmetropic eye can be divided into three stages:
1. The phase of rapid postnatal growth, when during the first 18 months of life the length of the eye increases by 3.7-3.8 mm.
2. Slower phase, between the ages of two and five years, the length of the eye increases by 1.1-1.2 mm.
3. The slow juvenile phase, which lasts until the age of 13 years, the length of the eye increases by another 1.3-1.4 mm, after which the growth of the eye in length is minimal.

Antero-posterior size and growth rate of the eye from 20 weeks of gestation to three years of age. Relationships between various structures of the eye during growth.
Ultrasound examination results.
Anterior-posterior eye size in boys (mm).

Dimensions of extraocular muscles and sclera

The fastest eye growth rate is observed in the first six months of life. All its sizes increase. At birth, the size of the cornea and iris is approximately 80% of the size of the cornea and iris of an adult.

The posterior segment, on the contrary, grows to a greater extent in the postnatal period. Consequently, this creates additional difficulties in predicting the results of surgical treatment of strabismus in very young children.

The thickness of the sclera at 6, 9 and 20 months of age is 0.45 mm, the same as in adult eyes.




Indications for ultrasound of the eyes

  • clouding of optical media;
  • intraocular and intraorbital tumors;
  • intraocular foreign body (its identification and localization);
  • orbital pathology;
  • measurement of parameters of the eyeball and orbit;
  • eye injuries;
  • intraocular hemorrhages;
  • retinal detachment;
  • pathology of the optic nerve;
  • vascular pathology;
  • condition after eye surgery;
  • myopic disease;
  • evaluation of ongoing treatment;
  • congenital anomalies of the eyeballs and orbits.

Contraindications for eye ultrasound

  • wounds of the eyelids and periorbital area;
  • open eye injuries;
  • retrobulbar bleeding.

Normal indicators on ultrasound of the eyes

  • The image shows the posterior capsule of the lens, but the lens itself is not visible;
  • the vitreous body is transparent;
  • eye axis 22.4 - 27.3 mm;
  • refractive power for emmetropia: 52.6 - 64.21 D;
  • the optic nerve is represented by a hypoechoic structure 2 - 2.5 mm;
  • thickness of internal shells 0.7-1 mm;
  • anterior-posterior axis of the vitreous body 16.5 mm;
  • the volume of the vitreous body is 4 ml.

Principles of ultrasound examination of the eye

Ultrasound of the eye is based on the principle of echolocation. When performing an ultrasound scan, the doctor sees an inverted image in black and white on the screen. Depending on the ability to reflect sound (echogenicity), the tissues are painted white. The denser the tissue, the higher its echogenicity and the whiter it appears on the screen.

  • hyperechoic (white): bones, sclera, vitreous fibrosis; air, silicone fillings and IOLs give a “comet tail”;
  • isoechoic (light gray color): fiber (or slightly increased), blood;
  • hypoechoic (dark gray color): muscles, optic nerve;
  • anechoic (black): lens, vitreous body, subretinal fluid.

Echostructure of tissues (character of distribution of echogenicity)

  • homogeneous;
  • heterogeneous.

Ultrasound tissue contours

  • normally smooth;
  • uneven: chronic inflammation, malignant formation.

Ultrasound of the vitreous

Vitreous hemorrhages

Occupy limited space.

Fresh - blood clot (formation of moderately increased echogenicity, heterogeneous structure).

Absorbable - a finely punctuated suspension, often delimited from the rest of the vitreous by a thin film.

Hemophthalmos

Occupy most of the vitreal cavity. A large mobile conglomerate of increased echogenicity, which can later be replaced by fibrous tissue; partial resorption is replaced by the formation of moorings.

Mooring lines

Rough cords fixed to the inner shells.

Retrovitreal hemorrhage

A finely punctuated suspension in the posterior pole of the eye limited by the vitreous body. It may have a V-shape, simulating retinal detachment (with hemorrhage, the outer boundaries of the “funnel” are less clear, the apex is not always connected with the optic disc).

Posterior vitreous detachment

It looks like a floating film in front of the retina.

Complete vitreous detachment

Hyperechoic ring of the vitreous boundary layer with destruction of the inner layers, anechoic zone between the ring and the retina.

Retinopathy of prematurity

On both sides behind the transparent lenses there are fixed layered coarse opacities. At grade 4, the eye is reduced in size, the membranes are thickened, compacted, and there is rough fibrosis in the vitreous body.

Hyperplasia of the primary vitreous

Unilateral buphthalmos, small anterior chamber, often cloudy lens, fixed layered coarse opacities behind.

Ultrasound of the retina

Retinal detachment

Flat (height 1 - 2 mm) - differentiate with preretinal membrane.

High and dome-shaped - differentiate with retinoschisis.

Fresh - the detached area in all projections is connected to the adjacent area of ​​the retina, is equal to it in thickness, ripples during a kinetic test, pronounced folding, pre- and subretinal tractions are often found at the top of the dome of the detachment, the site of the rupture can rarely be seen. Over time, it becomes more rigid and, if widespread, lumpy.

V-shaped - a filmy hyperechoic structure, fixed to the membranes of the eye in the area of ​​the optic disc and the dentate line. Inside the “funnel” there is fibrosis of the vitreous body (hyperechoic layered structures), outside there is anechoic subretinal fluid, but in the presence of exudate and blood, echogenicity increases due to small-point suspension. Differentiate with organized retrovitreal hemorrhage.

As the funnel closes, it acquires a Y-shape, and when the completely detached retina fusions, it acquires a T-shape

Epiretinal membrane

It can be fixed to the retina by one of the edges, but there is a section that extends into the vitreous body.

Retinoschisis

The exfoliated area is thinner than the adjacent one and is rigid during the kinetic test. A combination of retinal detachment with retinoschisis is possible - in the detached area there is a round, regular-shaped “encapsulated” formation.

Ultrasound of the choroid

Posterior uveitis

Thickening of the internal membranes (thickness more than 1 mm).

Detachment of the ciliary body

A small film behind the iris exfoliated with anechoic fluid.

Choroidal detachment

From one to several dome-shaped membranous structures of varying heights and lengths, between the detached areas there are jumpers where the choroid is fixed to the sclera; during the kinetic test, the bubbles are motionless. The hemorrhagic nature of the subchoroidal fluid is visualized as a finely punctuated suspension. Its organization creates the impression of a solid education.

Coloboma

Severe protrusion of the sclera occurs more often in the lower parts of the eyeball, often involving the lower parts of the optic disc, has a sharp transition from the normal part of the sclera, the vascular is absent, the retina is underdeveloped, covers the fossa or is detached.

Staphyloma

A protrusion in the area of ​​the optic nerve, the fossa is less pronounced, with a smooth transition to the normal part of the sclera, occurs when the POV of the eye is 26 mm.

Ultrasound of the optic nerve

Congestive optic disc

Hypoechoic prominence? > 1 mm? with a surface in the form of an isoechoic strip, possible expansion of the perineural space in the retrobulbar region (3 mm or more). Bilateral stagnant disc occurs with intracranial processes, unilateral - with orbital

Bulbar neuritis

Isoechoic prominence? > 1 mm? with the same surface, thickening of the internal membranes around the optic disc

Retrobulbar neuritis

Expansion of the perineural space in the retrobulbar region (3 mm or more) with uneven, slightly blurred boundaries.

Disc ischemia

A picture of a stagnant disc or neuritis, accompanied by hemodynamic disturbances.

Druze

Prominent hyperechoic round formation

Coloboma

Combined with choroidal coloboma, a deep optic disc defect of varying width, deforming the posterior pole and continuing into the image of the optic nerve

Ultrasound for foreign bodies in the eye

Ultrasound signs of foreign bodies: high echogenicity, “comet tail”, reverberation, acoustic shadow.

Ultrasound for large intraocular formations

Patient examination

The diagnostic algorithm should be followed:

  • carry out VDS;
  • if a vascular network is detected, perform pulsed wave Doppler;
  • in triplex ultrasound mode, assess the degree and nature of vascularization, quantitative hemodynamic indicators (necessary for dynamic monitoring);
  • echodensitometry: carried out using the "Histogram" function under standard scanner settings, except for G (Gain) (you can select 40 - 80 dB).
    T is the total number of pixels of any shade of gray in the area of ​​interest.
    L - level of shade of gray color prevailing in the area of ​​interest.
    M is the number of pixels of the shade of gray that predominates in the area of ​​interest
    Calculation
    Homogeneity index: IH = M / T x 100 (melanoma detection accuracy 85%)
    Echogenicity index: IE = L/G (melanoma detection accuracy 88%);
  • triplex ultrasound in dynamics.

Melanoma

A wide base, a narrower part - a leg, a wide and rounded cap, a heterogeneous hypo-, isoechoic structure, with CDS the development of its own vascular network is detected (a feeding vessel growing along the periphery is almost always determined, vascularization varies from a dense network to single vessels, or " avascular” due to the small diameter of the vessels, stasis, low blood flow velocity, necrosis); rarely may have an isoechoic homogeneous structure.

Hemangioma

Small hyperechoic heterogeneous prominence, disorganization and proliferation of the pigment epithelium over the lesion with the formation of multilayer structures and fibrous tissue, possible deposition of calcium salts; arterial and venous type of blood flow in CDS, slow growth, may be accompanied by secondary retinal detachment.

Sources

Expand
  1. Zubarev A.V. - Diagnostic ultrasound. Ophthalmology (2002)

The anterior-posterior ocular axis is an imaginary line that runs parallel between the medial and lateral reticulum at a 45-degree angle.

The axis connects the poles of the eyes.

It can be used to determine the distance from the tear film to the pigmented part of the retina. In simple terms, the axis helps determine the length and size of the eyes. These indicators are very important in the diagnosis of many diseases.

The front-rear axle has the following dimensions:

  • norm – up to 24.5 mm;
  • newborn children – 18 mm;
  • for farsightedness – 22 mm;
  • for myopia – 33 mm.

Considering these indicators, it can be noted that newborn children have the lowest indicators. All babies are farsighted, but eye growth stops before age three. At about 10 years of age, a child develops normal vision. The axis size is approaching 20 mm.

Genetics plays an important role in the development of eye length. In an adult, the anterior-posterior axis is no more than 24 mm. But there are exceptions when this mark grows to 27 mm. This is affected by a person's height. Final growth ceases with the active development of the human body.

If the eyes constantly get used to the stress of insufficient lighting, then myopia begins to develop. Then the PZO indicators will be pathological. The risk of developing myopia is the same in children and adults, especially if they write in low light. Failure to protect your vision significantly increases the risk of developing myopia.

It is imperative to monitor PZO indicators if there are suspicions of refractive errors in children and adolescents. This method is currently the only one for diagnosing and monitoring the progression of myopia. As the child ages, the length of the eye reaches normal levels.


For each person, length indicators may differ from the norm. In this case, the development of pathological changes or diseases is not observed. Each person's body is individual. Interestingly, eyeball length may have a genetic inheritance. The final size measurement can be taken when a person's growth stops.

If the size of the PZO is not associated with genetics, then the development of myopia is associated with work activity or the educational process. In this case, the eyes begin to get used to uncomfortable conditions.

Children often encounter this phenomenon when they start going to school. In adults, myopia develops due to work activity, especially if you often have to work at a computer in low light. Therefore, it is important to give your eyes a rest during such work. Adequate sleep will be especially beneficial. Only in this case can the eyes completely relax.

Doctors distinguish such a thing as accommodation. This involves an automatic process that allows, by changing the shape of the lens, to see objects clearly and clearly at different distances. It is worth noting that accommodation has an acquired and congenital form. If your eyes are constantly strained when working close, they begin to get used to such conditions. It is important to constantly monitor PZO indicators.

Every person should visit an ophthalmologist periodically. This will help avoid the development of serious diseases and pathological processes. In children under 10 years of age, PZO indicators may change and differ from the norm. This is considered normal because the eyeball is still developing. Each person's indicators may be different.

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The tissues of the eyeball are a set of acoustically heterogeneous environments. When an ultrasonic wave hits the interface between two media, it undergoes refraction and reflection. The more the acoustic resistances (impedances) of the boundary media differ, the larger part of the incident wave is reflected. The phenomenon of reflection of ultrasonic waves is used to determine the topography of normal and pathologically altered biological media.

Ultrasound is used to diagnose intravital measurements of the eyeball and its anatomical and optical elements. This is a highly informative instrumental method, an addition to generally accepted clinical methods of ophthalmological diagnostics. As a rule, echography should be preceded by a traditional anamnestic and clinical-ophthalmological examination of the patient.

The study of echobiometric (linear and angular values) and anatomical-topographic (localization, density) characteristics is carried out according to the main indications. These include the following.

  • The need to measure the thickness of the cornea, the depth of the anterior and posterior chambers, the thickness of the lens and inner membranes of the eye, the length of CT, various other intraocular distances and the size of the eye as a whole (for example, with foreign bodies in the eye, subatrophy of the eyeball, glaucoma, myopia, when calculating optical strength of intraocular lenses (IOLs)).
  • Study of the topography and structure of the anterior chamber angle (ACA). Assessment of the condition of surgically formed outflow tracts and the UPC after antiglaucoma interventions.
  • Assessment of IOL position (fixation, dislocation, fusion).
  • Measuring the extent of retrobulbar tissues in various directions, the thickness of the optic nerve and the rectus muscles of the eye.
  • Determination of the magnitude and study of the topography of pathological changes, including neoplasms of the eye, retrobulbar space; quantitative assessment of these changes over time. Differentiation of various clinical forms of exophthalmos.
  • Assessment of the height and extent of detachment of the ciliary body, choroid and retina of the eye during difficult ophthalmoscopy.
  • Detection of destruction, exudate, opacities, blood clots, mooring in the CT, determination of the features of their localization, density and mobility
  • Identification and determination of the localization of intraocular foreign bodies, including clinically invisible and X-ray negative, as well as assessment of the degree of their encapsulation and mobility, and magnetic properties.

Operating principle

Ultrasound examination of the eye is carried out using contact or immersion methods.

Contact method

Contact one-dimensional echography is carried out as follows. The patient is seated in a chair to the left and slightly in front of the diagnostic ultrasound device, facing the doctor, who is sitting in front of the device screen half-turned towards the patient. In some cases, an ultrasound scan is possible with the patient lying face up on the couch (the doctor is located at the head of the patient).

Before the examination, an anesthetic is instilled into the conjunctival cavity of the eye being examined. With his right hand, the doctor brings the ultrasound probe, sterilized with 96% ethanol, into contact with the patient’s eye being examined, and with his left hand he regulates the operation of the device. The contact medium is tear fluid.

An acoustic examination of the eye begins with a review using a probe with a piezoelectric plate diameter of 5 mm, and the final conclusion is given after a detailed examination using a probe with a piezoelectric plate diameter of 3 mm.

Immersion method

The immersion method of acoustic examination of the eye assumes the presence of a layer of liquid or gel between the piezoelectric plate of the diagnostic probe and the eye being examined. Most often, this method is implemented using ultrasound equipment, based on the use of the B-method of echography. A diagnostic probe scanning along a different trajectory “floats” in an immersion medium (degassed water, isotonic sodium chloride solution), located in a special attachment that is installed on the eye of the subject. The diagnostic probe may also be housed in a housing with a sound-transparent membrane, which is brought into contact with the closed eyelids of the patient sitting in a chair. In this case, instillation anesthesia is not needed.

Research methodology

  • One-dimensional echography (A-method)- a fairly accurate method that allows you to graphically identify various pathological changes and formations, as well as measure the size of the eyeball and its individual anatomical and optical elements and structures. The method has been modified into a separate special direction - ultrasound biometrics.
  • Two-dimensional echography (acoustic scanning, B-method)- is based on the transformation of the amplitude gradation of echo signals into light points of varying degrees of brightness, forming an image of a cross-section of the eyeball on the monitor.
  • UBM. Digital technologies have made it possible to develop a UBM method based on digital analysis of the signal of each piezoelectric element of the sensor. The resolution of the UBM at the axial scanning plane is 40 µm. For this resolution, 50-80 MHz sensors are used.
  • Three-dimensional echography. Three-dimensional echography reproduces a three-dimensional image by adding and analyzing multiple planar echograms or volumes while moving the scanning plane vertically-horizontally or concentrically around its central axis. Obtaining a volumetric image occurs either in real time (interactively) or delayed depending on the sensors and processor power.
  • Power Dopplerography(power Doppler mapping) - a method of analyzing blood flow, consists of displaying numerous amplitude and speed characteristics of red blood cells, the so-called energy profiles.
  • Pulsed wave dopplerography allows you to objectively judge the speed and direction of blood flow in a particular vessel and examine the nature of the noise.
  • Ultrasound duplex examination. Combining pulsed Dopplerography and gray scale scanning in one device allows you to simultaneously assess the condition of the vascular wall and record hemodynamic parameters. The main criterion for assessing hemodynamics is linear blood flow velocity (cm/s).

The algorithm for acoustic examination of the eye and orbit consists in the consistent application of the principle of complementarity of survey, localization, kinetic and quantitative echography.

  • Survey echography is performed to identify asymmetry and the focus of pathology.
  • Localization echography allows using echobiometry to measure various linear and angular parameters of intraocular structures and formations and determine their anatomical and topographic relationships.
  • Kinetic echography consists of a series of repeated ultrasounds after rapid movements of the subject's eye (changes in the direction of the patient's gaze). The kinetic test makes it possible to determine the degree of mobility of the detected formations.
  • Quantitative echography gives an indirect idea of ​​the acoustic density of the structures being studied, expressed in decibels. The principle is based on a gradual decrease in echo signals until they are completely suppressed.

The task of preliminary ultrasound is to visualize the main anatomical and topographic structures of the eye and orbit. For this purpose, scanning in gray scale mode is carried out in two planes:

  • horizontal (axial), passing through the cornea, eyeball, internal and external rectus muscles, optic nerve and apex of the orbit;
  • vertical (sagittal), passing through the eyeball, superior and inferior rectus muscles, optic nerve and apex of the orbit.

A prerequisite for ensuring the greatest information content of ultrasound is the orientation of the probe at a right (or close to a right) angle in relation to the structure (surface) being studied. In this case, the echo signal of maximum amplitude coming from the object under study is recorded. The probe itself should not put pressure on the eyeball.

When examining the eyeball, it is necessary to remember its conditional division into four quadrants (segments): upper and lower external, upper and lower internal. The central zone of the fundus with the optic disc and macular region located in it is especially distinguished.

Characteristics in normal and pathological conditions

As the scanning plane passes approximately along the anteroposterior axis of the eye, echo signals are received from the eyelids, cornea, anterior and posterior surfaces of the lens, and retina. The transparent lens is not detected acoustically. Its posterior capsule is visualized more clearly in the form of a hyperechoic arch. CT is normal, acoustically transparent.

When scanning, the retina, choroid and sclera actually merge into a single complex. At the same time, the internal membranes (reticular and vascular) have a slightly lower acoustic density than the hyperechoic sclera, and their thickness together is 0.7-1.0 mm.

In the same scanning plane, a funnel-shaped retrobulbar part is visible, limited by the hyperechoic bone walls of the orbit and filled with fine-grained fatty tissue of average or slightly increased acoustic density. In the central zone of the retrobulbar space (closer to the nasal part), the optic nerve is visualized in the form of a hypoechoic tubular structure about 2.0-2.5 mm wide, emanating from the eyeball on the nasal side at a distance of 4 mm from its posterior pole.

With the appropriate orientation of the sensor, scanning plane and direction of view, an image of the rectus oculi muscles is obtained in the form of homogeneous tubular structures with a lower acoustic density than fatty tissue, with a thickness of 4.0-5.0 mm between the fascial layers.

When the lens is subluxated, varying degrees of displacement of one of its equatorial edges in the CT are observed. When dislocated, the lens is revealed in various layers of the CT or in the fundus. During the kinetic test, the lens either moves freely or remains fixed to the retina or fibrous strands of the CT. In aphakia, during ultrasound, trembling of the iris that has lost support is observed.

When replacing the lens with an artificial IOL, a formation of high acoustic density is visualized behind the iris.

In recent years, great importance has been attached to the echographic study of the structures of the UPC and the iridociliary zone as a whole. Using UBM, three main anatomical and topographical types of the structure of the iridociliary zone are identified, depending on the type of clinical refraction.

  • The hypermetropic type is characterized by a convex profile of the iris, a small iridocorneal angle (17±4.05°), a characteristic anteromedial attachment of the iris root to the ciliary body, providing a beak-shaped IPC with a narrow entrance (0.12 mm) to the angle bay and a very close location of the iris with trabecular zone. With this anatomical and topographical type, favorable conditions arise for mechanical blockade of the UPC with iris tissue.
  • Myopic eyes with a reverse iris profile, iridocorneal angle (36.2+5.25°), a large area of ​​contact of the iris pigment layer with the zonular ligaments and the anterior surface of the lens are predisposed to the development of pigment disperse syndrome.
  • Emmetropic eyes are the most common type, characterized by a straight iris profile with an average AUC value of 31.13±6.24°, a posterior chamber depth of 0.56±0.09 mm, a relatively wide entrance to the AUC bay - 0.39±0, 08 mm, anteroposterior axis - 23.92+1.62 mm. With this design of the iridociliary zone there is no obvious predisposition to hydrodynamic disturbances, i.e. There are no anatomical and topographic conditions for the development of pupillary block and pigment-dispersed syndrome.

Changes in the acoustic characteristics of CT occur as a result of degenerative-dystrophic, inflammatory processes, hemorrhages, etc. Opacities can be floating or fixed; dotted, filmy, in the form of lumps and conglomerates. The degree of opacification varies from barely noticeable to rough moorings and pronounced continuous fibrosis.

When interpreting ultrasound data hemophthalmos you should remember the stages of its course

  • Stage I - corresponds to the processes of hemostasis (2-3 days from the moment of hemorrhage) and is characterized by the presence of coagulated blood in the CT of moderate acoustic density.
  • Stage II is the stage of hemolysis and diffusion of hemorrhage, accompanied by a decrease in its acoustic density and blurred contours. During the process of resorption, against the background of hemolysis and fibrinolysis, a finely punctuated suspension appears, often delimited from the unchanged part of the CT by a thin film. In some cases, in the stage of hemolysis of erythrocytes, ultrasound turns out to be uninformative, since the blood elements are commensurate with the length of the ultrasound wave and the hemorrhage zone is not differentiated.
  • Stage III is the stage of initial connective tissue organization, occurs in cases of further development of the pathological process (repeated hemorrhages) and is characterized by the presence of local areas of increased density.
  • Stage IV is the stage of developed connective tissue organization or mooring, characterized by the formation of moorings and films of high acoustic density.

With CT detachment A membrane of increased acoustic density is visualized echographically, corresponding to its dense boundary layer, separated from the retina by an acoustically transparent space.

Clinical symptoms indicating the possibility retinal detachment- one of the main indications for ultrasound. With the A-method of echography, the diagnosis of retinal detachment is based on the persistent registration of an isolated echo signal from the detached retina, separated by an isoline section from the echo signals of the sclera plus retrobulbar tissue complex. This indicator is used to judge the height of retinal detachment. With the B-method of echography, retinal detachment is visualized in the form of a film-like formation in the retina, usually having contact with the membranes of the eye in the projection of the dentate line and optic disc. In contrast to total retinal detachment, with local retinal detachment, the pathological process occupies a certain segment of the eyeball or part of it. The detachment can be flat, 1-2 mm high. Local detachment can be higher, sometimes dome-shaped, which makes it necessary to differentiate it from a retinal cyst.

One of the important indications for echographic examination is the development of detachment of the choroid and ciliary body, in some cases occurring after anti-glaucoma operations, cataract extraction, contusion and penetrating wounds of the eyeball, and uveitis. The researcher’s task is to determine the quadrant of its location and flow dynamics. To detect ciliary body detachment, the extreme periphery of the eyeball is scanned in various projections at the maximum angle of inclination of the sensor without a water nozzle. If there is a sensor with a water attachment, the anterior parts of the eyeball are examined in transverse and longitudinal sections.

The detached ciliary body is visualized as a filmy structure located 0.5-2.0 mm deeper than the scleral membrane of the eye as a result of the spread of acoustically homogeneous transudate or aqueous humor underneath it.

Ultrasonic signs of choroidal detachment are quite specific: from one to several clearly contoured membranous tubercles of varying heights and lengths are visualized, while between the detached areas there are always bridges where the choroid is still fixed to the sclera: during the kinetic test, the bubbles are motionless. Unlike retinal detachment, the contours of the tubercles are usually not adjacent to the optic disc area.

Choroidal detachment can occupy all segments of the eyeball from the central zone to the extreme periphery. With a pronounced high detachment, the choroidal bubbles come closer to each other and give the picture of a “kissing” detachment of the choroid.

Prerequisite for visualization foreign body- difference in the acoustic density of the foreign body material and the tissues surrounding it. With the A-method, a signal from a foreign body appears on the echogram, by which one can judge its location in the eye. An important criterion for differential diagnosis is the immediate disappearance of the echo signal from the foreign body with a minimal change in the probing angle. Due to their composition, shape and size, foreign bodies can cause various ultrasonic effects, such as “comet tail”. To visualize fragments in the anterior part of the eyeball, it is better to use a sensor with a water attachment.

Generally in good condition ONH with ultrasound not differentiated. The ability to assess the state of the optic disc both normally and in pathologies has expanded with the introduction of color Doppler mapping and energy mapping methods.

In case of stagnation due to non-inflammatory edema on B-scanograms, the optic disc increases in size and protrudes into the CT cavity. The acoustic density of the edematous disc is low, only the surface stands out in the form of a hyperechoic strip.

Among intraocular neoplasms, creating the “plus-tissue” effect in the eye, the most common are melanoma of the choroid and ciliary body (in adults) and retinoblastoma (RB) (in children). With the A-method of research, a neoplasm is detected in the form of a complex of echo signals that merge with each other, but never decrease to an isoline, which reflects a certain acoustic resistance of the homogeneous morphological substrate of the neoplasm. The development of areas of necrosis, vessels, and lacunae in melanoma is echographically verified by an increase in the difference in the amplitudes of echo signals. With the B-method, the main sign of melanoma is the presence on the scanogram of a clear contour corresponding to the boundaries of the tumor, while the acoustic density of the formation itself can be of varying degrees of homogeneity.

During acoustic scanning, the location, shape, clarity of contours, size of the tumor are determined, its acoustic density is quantitatively assessed (high, low), and the nature of the density distribution is qualitatively assessed (homogeneous or heterogeneous).

Thus, the possibilities of using diagnostic ultrasound in ophthalmology are constantly expanding, which ensures dynamism and continuity in the development of this area.