Pachymetry in ophthalmology - the thickness of the cornea is normal in adults. Deciphering keratometry: the shape and structure of the cornea The size of the cornea of \u200b\u200bthe eye is normal

It is a transparent lens of the eye, concave on the inside and convex on the outside. It consists of several lamellas (layers), through the limbus (thin fibrous fibers) attached to the sclera. Corneal layer healthy person has an average thickness of 515 microns. The parameters of the thin cornea are 481-520 microns. Ultra-thin has a thickness of 430 to 480 microns. Thanks to the cornea, light rays are refracted and transmitted to the retina. In some cases, it can become thinner due to a weakening of the connection between the collagen fibers of its inner layers. This process is dangerous, it can lead to loss of the organ of vision.

The main role in the thinning of the stratum corneum is attributed to a hereditary factor. If one or both parents were diagnosed with such a pathology, then children with a 25-50% probability will have it.

In addition, the causes of pathology lie in the following:

• frequent exposure to ultraviolet radiation;
• negative impact of the environment;
• some genetic abnormalities (Down syndrome);
• high degree of myopia;
• (a disease in which the cornea, under the influence of intraocular pressure, begins to protrude strongly and becomes like a cone).

As a result of thinning of the stratum corneum, its shape changes, turbidity is observed.

Diagnostics

To establish the diagnosis and timely eliminate the thinned cornea, it is necessary to undergo a number of procedures. They are reflected in the following table.

1. Pachymetry (keratopachymetry). Measurement of corneal thickness using ultrasound.
2. Refractomy. With the help of the procedure, associated vision problems (astigmatism, myopia) are identified.
3. Skiascopy. Determination of the ability of the eye to refract light.
4. Ophthalmoscopy. Examination with a slit lamp to assess the vessels of the fundus, retina, the state of the optic nerve.
5. Biomicroscopy. Helps to identify the opacity of the stratum corneum, cracks in the membrane, proliferation of nerve endings.
6. Keratotopography. Graphical representation of the corneal relief.

Conservative therapy

Carrying out instillations of drops, which eliminate eye discomfort, activate the regenerative capacity of the cornea. These are Taufon, Floxal, Oftan Katakhrom. Apply hormonal drugs, for example, Maxidex, vitamin complexes, immunostimulants, anti-inflammatory drugs (Naklof), Emoxipin injections. Additionally, magnetotherapy, phonophoresis, Sidorenko glasses are prescribed.

Operations

Laser vision correction for thin corneas is not always indicated. This type of operation is based on thinning the stratum corneum so that the light rays are focused precisely on the retina. And the higher the degree of myopia, astigmatism, hyperopia, the thicker the lamella will need to be removed. Therefore, the thickness of the stratum corneum is the main indicator that is assessed before vision correction.

PRK (photorefractive keratectomy)

Pretty old operation for vision correction, which has been practiced for over 30 years. The essence lies in the removal of the corneal epithelium and further evaporation of the required number of lamellas with a laser beam.

LASIK

The operation differs in that the upper layers are not completely removed, but only cut off during the operation. At the end, the flap is returned to its place. But here, too, there are some nuances. The surface layer of the cornea is very similar in consistency to jelly and cannot maintain its shape on its own, so the flap is cut along with a denser and deeper layer (stroma).

Healing after vision correction is faster, but the thickness of the stroma decreases and a thick lens can no longer be cut out in it. This is the main reason why traditional LASIK is not performed with a thin stratum corneum.

Femtolasik

The procedure is based on cutting off a flap of the upper lamellas with a laser beam and partial evaporation of the lower ones. The effectiveness of femtolasik for a thin cornea depends on how much thickness remains after the correction. Femtolasik with a thin cornea is carried out contactlessly using a femtosecond laser beam. The upper flap is engrafted using a seamless method.

In LASIK operations, a flap with a minimum thickness of 130 µm is removed, when exposed to a femtosecond laser - this figure is 100 µm. Correction of one diopter requires an average of 10-15 microns of corneal tissue.

Ophthalmologists recommend Femtolasik with a thin cornea more often than just LASIK, since no mechanical effect is exerted on the lamellae, the procedure is carried out contactlessly using infrared radiation. The laser sends pulses to the lamellas, resulting in the formation of microscopic bubbles. They gradually merge with each other, forming a delamination plane. Then the doctor removes the formed valve and performs laser vision correction.

The operation forms a perfect delamination surface connective tissue without mechanical stress.

The cornea is located in the outermost layer and acts as a kind of frame. Normally, it is transparent and part of the conductive system. eyeball.

The structure of the cornea of \u200b\u200bthe eye

The shape of the cornea resembles, it is convex-concave. In the structure of the cornea, five layers are distinguished, which are located from outside to inside:

1. Stratified squamous epithelium that covers the cornea. It protects it from damaging effects and ensures the exchange of air and heat. It also maintains the spherical shape of the cornea.
2. Bowman's membrane is very durable and helps to maintain a certain shape.
3. The stromal layer consists of a huge amount of collagen, the fibers of which are closely intertwined. In addition, it contains leukocytes, which provide immune protection from pathogenic microbes. Fibrocytes, located in the stroma, produce collagen, maintaining its balance.
4. Descemet's membrane is resistant to impact high temperatures and infections.
5. The single-layer endothelium is semipermeable and permeable nutrientscoming from aqueous humor. If the function of this layer is impaired, edema occurs, which prevents the cornea from feeding normally. There are no other pathways for metabolism in this case, since there are no blood vessels in the cornea. This valuable property helps to transplant donor flaps without fear of possible rejection.

Physiological role of the cornea

The cornea has several functions:

• Support;
• Protective;
• Refractive;
• Conductive.

All this becomes possible thanks to such characteristics of the cornea as:

• Strength;
• High sensitivity to various stimuli;
• Fast regeneration;
• Transparency for light streams;
• Spherical shape;
• Lack of blood vessels;
• Specularity.

Video about the structure of the cornea

Corneal lesion symptoms

Corneal pathology can be suspected based on the following symptoms:

• Corneal reshaping;
• Decreased visual acuity;
• His ;
• Pain in the eyeball;
• Narrowing of visual fields;

Diagnostic methods for corneal lesions

In case of suspicion of corneal pathology, it is necessary to conduct an examination:

• Side ray visualization;
• eyes;
• Bacteriological research;
• Keratotopography.

With corneal pathology, it is usually possible to identify the following diagnostically significant signs:

• Change in the shape or size of the cornea;
• Lack of mirror shine;
• The presence of corneal opacities;
• Formation of abnormal vessels;
• Spasm.

In conclusion, I would like to remind you that the cornea is an important structure of the eyeball. If its structure is disturbed, dysfunction of both the cornea and the entire optical system occurs. In order to diagnose the pathological process in time, it is necessary to carry out additional examination methods. This will allow the appointment of timely and effective treatment.

The cornea, or cornea, is convex in front and concave in the back, transparent, avascular plate of the eyeball, which is a direct continuation of the sclera. The cornea in humans occupies about 1/6 of the outer shell of the eye. It has the form of a convex-concave lens, the place of its transition to the sclera (limb) looks like a translucent ring up to 1 mm wide. Its presence is explained by the fact that the deep layers of the cornea extend posteriorly a little further than the anterior ones.

Diameter the cornea is almost an absolute constant and is 10 ± 0.56 mm, but the vertical dimension is usually 0.5-1 mm less than the horizontal. In the center, its thickness is 450-600 microns, and at the periphery - 650-750 microns. This indicator also correlates with age: for example, at 20-30 years old, the thickness of the cornea is 0.534 and 0.707 mm, and at 71-80 years old - 0.518 and 0.618 mm.

Distinctive qualities of the cornea:

• Spherical (radius of curvature of the front surface ~ 7.7 mm, back 6.8 mm)
• Mirror-shiny
• Deprived of blood vessels
• Possesses high tactile and painful, but low temperature sensitivity
• Refracts light rays with a force of 40-43 diopters.

Function

The cornea is the optical structure of the eye, its refractive power averages 45D (diopters) in children in the first year of life, and about 40D by the age of 7, as in adults. The refractive power of the cornea in the vertical meridian is somewhat greater than in the horizontal one (physiological astigmatism).

Dimensions

• The horizontal diameter in adults is 11 mm (in newborns - 9 mm).
• The vertical diameter is 10 mm, in newborns it is 8 mm.
• Thickness in the center - 0.4-0.6 mm, in the peripheral part - 0.8-1.2 mm.
• The radius of curvature of the anterior surface of the cornea in adults is 7.5 mm, in newborns - 7 mm.

Corneal growth is accomplished by thinning and stretching the tissue.

Corneal composition

The cornea contains water, collagen of mesenchymal origin, mucopolysaccharides, proteins (albumin, globulin), lipids, vitamins. The transparency of the cornea depends on the correct location of structural elements and the same refractive indices, as well as the content of water in it (normally up to 75%; an increase in water over 86% leads to corneal opacity).

Corneal changes in old age

• the amount of moisture and vitamins decreases,
• globulin fractions of proteins prevail over albumin,
• calcium salts and lipids are deposited.

In this regard, first of all, the area of \u200b\u200btransition of the cornea to the sclera - the limbus - changes: the surface layers of the sclera seem to move towards the cornea, while the inner layers lag behind; the cornea becomes like a glass inserted into the bezel of a watch. In connection with metabolic disorders, the so-called senile arch is formed, the sensitivity of the cornea decreases.

Corneal structure

1. Surface layer the cornea is a squamous stratified epithelium, which is a continuation of the connective membrane of the eye (conjunctiva). The thickness of the epithelium is 0.04 mm. This layer regenerates well and quickly in case of damage, leaving no clouding. The epithelium has a protective function and is a regulator of the water content in the cornea. The corneal epithelium, in turn, is protected from the external environment by the so-called liquid, or hilar, layer.
2. Anterior boundary plate - Bowman's membrane is loosely connected with the epithelium, therefore, with pathology, the epithelium can be easily rejected. It is structureless, inelastic, homogeneous, has a low level of metabolism, is incapable of regeneration, therefore, if it is damaged, opacities remain. The thickness is 0.02 mm in the center and less at the periphery.
3. Corneal intrinsic substance (stroma) - a thick, transparent middle layer, consisting of thin connective tissue, regularly spaced plates containing collagen fibrils, in which are located single wandering cells - fibroblasts and lymphoid elements that perform a protective function. They are parallel and overlap like the pages of a book. For their better connection, a mucoprotein is located in the intervals between the layers. The stroma is up to 0.5 mm thick, has no vessels and consists of about 200 layers of mainly type I collagen fibrils.
4. Posterior border elastic plate (Descemet's membrane) is a thin acellular layer that serves as the basement membrane of the corneal endothelium, from which all cells develop. This layer consists mainly of type IV collagen fibers, which are more elastic than type I collagen. The thickness of this layer is about 5-20 microns, depending on the patient's age. In front of the descimet shell is a very thin but rather strong Duat layer, which is only 15 microns thick and has a load capacity of 1.5 to 2 bar of pressure, according to research.
5. Endothelium is the inner part of the cornea, facing the anterior chamber of the eye and washed with intraocular fluid. It consists of a single-layer squamous or cubic epithelium, the cells are rich in mitochondria, the layer thickness is about 0.05 mm. This layer protects the stroma from direct exposure to aqueous humor, while simultaneously providing metabolic processes between it and the cornea, it has a pronounced barrier function (unlike the epithelium of the surface layer of the cornea, the endothelium does not regenerate, instead, there is a continuous process of division, compensating for dead cells); participates in the formation of the trabecular apparatus of the iridocorneal angle.

Corneal physiology

The temperature of the cornea is about 10 ° C lower than the body temperature, which is due to the direct contact of the moist surface of the cornea with the external environment, as well as the absence of blood vessels in it. With closed eyelids, the temperature of the cornea at the limbus is 35.4 ° C, and in the center 35.1 ° C (with open eyelids ~ 30 ° C).

In this regard, the growth of molds with the development of specific keratitis is possible in it.

Since there are no lymphatic and blood vessels, nutrition and metabolism in the cornea occurs by osmosis and diffusion (due to the lacrimal fluid, moisture in the anterior chamber and pericorneal blood vessels).

The absence of blood vessels in the cornea is replenished with abundant innervation, which is represented by trophic, sensitive and vegetative nerve fibers... Metabolic processes in the cornea are regulated by trophic nerves extending from the trigeminal and facial nerves.

High sensitivity of the cornea is provided by the system of long ciliary nerves (from the orbital branch of the trigeminal nerve), which form the perilimbal nerve plexus around the cornea. When they enter the cornea, they lose the myelin sheath and become invisible. In the cornea, three tiers of nerve plexuses are formed - in the stroma, under the basal (Bowman's) membrane and subepithelially. The closer to the surface of the cornea, the thinner the nerve endings become and the denser their interlacing. Almost every cell of the anterior corneal epithelium is provided with a separate nerve ending. This explains the high tactile sensitivity of the cornea and the pronounced pain syndrome when sensitive endings are exposed (epithelial erosion).

The high sensitivity of the cornea underlies its protective function: when lightly touching the surface of the cornea and even when the wind blows, an unconditioned corneal reflex occurs - the eyelids close, the eyeball turns upward, removing the cornea from danger, and tear fluid appears, washing away dust particles.

The afferent part of the corneal reflex arc is carried trigeminal nerve, efferent - facial nerve... Loss of the corneal reflex occurs with severe brain damage (shock, coma). The disappearance of the corneal reflex is an indicator of the depth of anesthesia. The reflex disappears with some lesions of the cornea and upper cervical spinal cord.

The rapid direct reaction of the vessels of the marginal looped network to any irritation of the cornea occurs due to the fibers of the sympathetic and parasympathetic nerves present in the perilimbal nerve plexus. They are divided into 2 endings, one of which goes to the walls of the vessel, and the other penetrates into the cornea and contacts the branched network of the trigeminal nerve.

The eyeball is spherical. Most of its surface is covered with sclera - a dense connective membrane. It performs supporting and protective functions. In the front part of the eye, the sclera passes into the transparent cornea, which occupies 1/6 of the surface of the eyeball and takes over the main function of refracting light rays. It is she who is the optical medium, the properties of which determine visual acuity. The optical power of the cornea is 44 diopters.

Normally, the cornea is a transparent, avascular tissue. It contains a strictly defined amount of water and has an ordered structure. A healthy cornea is not only transparent, but also smooth and shiny. It is spherical and highly sensitive.

Corneal structure

The average corneal dimensions are: 11.5 mm vertically, 12 mm horizontally. The thickness of the stratum corneum varies from 500 microns in the center to 1 mm in the periphery. In the structure of the cornea, five layers are distinguished: anterior epithelium, Bowman's sheath, stroma, Descemet's sheath, and endothelium.

Front epithelial layer is a shell that is characterized by fast recovery. It is not subject to keratinization and does not form scars. The anterior epithelial layer performs the function of protection and is rapidly regenerated.

Bowman's shell (membrane) is a cell-free layer that forms scars when damaged.

Stroma the cornea is composed of collagen fibers oriented in a certain way. This layer occupies 90% of the entire thickness of the cornea. Its intercellular space is filled with chondroitin sulfate and keratan sulfate.

Descemet's shella consists of the finest collagen fibers and is the basement membrane of the endothelium. This layer prevents the infection from spreading into the eye.

Endothelium although it is a monolayer of hexagonal cells, it performs a number of important functions. In particular, this layer is involved in the nutrition of the cornea and maintains the stability of its state with changes in intraocular pressure. Unfortunately, the endothelium is completely devoid of the ability to regenerate, therefore, with age, the number of cells in this layer decreases and it becomes thinner.

The innervation of the cornea occurs at the endings of the first branch of the trigeminal nerve.

The cornea is surrounded by a network of blood vessels. Its nutrition is provided by capillaries, moisture in the anterior chamber, nerve endings, and a tear film.

Corneal reflex and corneal protective functions

The optical refraction function makes the cornea the first step in the work of the entire visual system. However, in addition to this, like the sclera, this part of the shell of the eyeball protects it from the external environment. In this case, it is the cornea that takes on all kinds of external influences (dust, wind, moisture, temperature changes).

Extreme sensitivity provides reliable protection not only for the deeper structures of the eye, but also for the cornea itself. The slightest irritation, fright, or a particle flashing in front of the eye, cause an unconditioned reflex - blinking, combined with lacrimation. This way the cornea protects itself from damage, bright light and other unwanted influences. When blinking, the eye rolls up under the eyelid and tears occur, washing away possible dust particles to the corner of the eye.

Corneal diseases and their symptoms

Changes in the shape and refractive power of the cornea

• The deviation of the curvature of the cornea towards greater steepness is characteristic of myopia.
• With farsightedness, the cornea has a more flattened shape than normal.
• Astigmatism is characterized by violations of the shape of the cornea in various planes.
• Megalocornea and microcornea - congenital anomalies corneal shape.

Damage to the superficial corneal epithelium

• Point erosion. Violation of the integrity of the corneal epithelium often accompanies various eye diseases. The cornea can be eroded due to improper selection of contact lenses, dry eye syndrome, lagophthalmos, spring catarrh, keratitis, and also as a reaction to some eye drops.
• Edema of the epithelium may be the result of a sharp jump in intraocular pressure or indicate damage to the endothelial layer.
• Punctate epithelial keratitis can accompany viral ophthalmic diseases. On examination, swollen granular epithelial cells are found.
• Filaments are mucous formations in the form of a comma. They can form against the background of keratoconjunctivitis, accompany recurrent erosion or dry eye syndrome. The threads are usually attached at one end to the surface of the cornea and are not washed away by the tear.

Damage to the corneal stroma

• The formation of infiltrates. Infiltrates result from active inflammation and are the areas of the cornea that are involved in this process. They can form from mechanical damage (for example, when wearing lenses) or have an infectious origin.
• Edema of the stroma. With the development of edema of the stroma, its thickening and loss of transparency are observed. The stroma can swell with keratitis, keratoconus, damage to the endothelium, Fuchs dystrophy, and also after surgical intervention before our eyes.
• Vascularization (vascular ingrowth). Normally, the cornea is an avascular tissue. Vessels can grow into its layers due to previous inflammatory diseases.

Damage to Descemet's sheath

• Ruptures can be a consequence of corneal trauma or as a complication of keratoconus.
• Folds are most often formed as a result of surgical trauma.

Corneal diagnostic methods

The cornea is examined in order to identify possible damage to its layers, as well as to assess its curvature as possible cause decrease in visual acuity. The following ophthalmic examinations are carried out:

• Corneal biomicroscopy. Standard examination of the cornea under an illuminated microscope. Such diagnostics can reveal most diseases, as well as trauma and changes in the curvature of the cornea.
• Pachymetry measures the thickness of the cornea. This examination is done using ultrasound.
• Mirror microscopy - examination of the endothelial layer by photography. In this case, the shape of the cells is analyzed and their number is calculated per 1 sq. mm of area. The normal density is considered to be 3000 cells per 1 sq. mm.
• Keratometry measures the curvature of the anterior corneal surface.
• Corneal topography - a complete computer study of the entire corneal area. Allows you to pointwise analyze the cornea by thickness, curvature and refractive power.
• Microbiological studies are aimed at studying the microflora of the corneal surface. The material for this study is collected under local drip anesthesia.
• Corneal biopsy is advisable in case of non-indicative or uninformative results of scrapings and cultures.

Basic principles of treatment of corneal diseases

Diseases caused by altered corneal curvature require correction with lenses or glasses. In severe cases, it may be necessary to correct refractive errors surgical treatment by laser surgery (LASIK and its derivatives).

Belma and corneal opacities are treated by the method of penetrating or layer-by-layer keratoplasty.

Corneal infections require antibacterial and antiviral drugs in the form of drops, tablets, injections.

Topical glucocorticoids help suppress inflammatory processes and prevent scarring (Dexamethasone and its derivatives).

With superficial injuries of the cornea, agents are widely used that accelerate the regeneration of epithelial tissues (Korneregel, Taufon, Solcoseryl, Balarpan, etc.).

In a number of diseases accompanied by dryness of the cornea, it is shown to moisturize the eye with tear-replacing drops (Sistain, Hilo-Komod and others)

For keratoconus, severe contact lenses, collagen crosslinking and implantation of inststromal segments (rings). In more severe cases, they resort to tight keratoplasty (corneal transplant).

The eyeball is one of the most sensitive organs of the human body. External influences can cause irreparable damage to the eyes. But no one is immune to development various diseases and pathologies.

Many vision problems arise from defects in the cornea, the most prominent part of the eye. Therefore, medicine requires an accurate and painless method for diagnosing the stratum corneum. Eye pachymetry has become the expected result of the search for such a diagnostic method.

What is the procedure

Changes in one of the functional parameters (corneal thickness, transparency, etc.) can lead to a decrease in the focusing power of the eye. As a consequence of problems with focusing and refraction, visual impairment occurs. After 55 years, it is recommended to conduct a pachymetry session once a year in order to prevent vision problems.

Doctors prescribe pachymetry to measure the thickness of the cornea. In some cases, pachymetry is used to dynamically monitor the condition of the cornea. This method helps to assess the likely pathology of the cornea, and is also a mandatory preoperative examination.

Clarification of the diagnosis is the cornerstone of medicine, necessary for planning and prescribing effective treatment.

Among the known pathologies diagnosed with pachymetry:

• - problems with the formation and removal of intraocular fluid can lead to chronic disturbances in intraocular pressure. The consequence of impaired IOP is damage to the nerve tissues of the eye, which provokes complete or partial blindness. When diagnosing this disease, after the pachymetry procedure, intraocular pressure is measured and appropriate treatment is prescribed;
• corneal edema - eye tissues are deformed and distorted. In this case, tearing and pain in the eyes, redness of the eyeball occur. There are several reasons for the occurrence of edema: poor hygiene when wearing, getting into the eyeball foreign bodies, allergies, inflammation of the corneal tissue, various eye injuries, etc. In this case, pachymetry will show local or general corneal thickening, local and widespread deformities and lesions;
• fuchs dystrophy - hereditary disease, which affects the inner layer of the cornea - the endothelium. This layer consists of special cells that pump excess moisture out of the cornea. Endothelial cells do not divide, which provokes the gradual development of the disease. Over time, due to excess moisture, the cornea becomes cloudy, vision decreases. Patients have an intolerance to bright light, a feeling of "sand" in the eyes, and inconsistent visual acuity. Due to the hereditary nature of the disease, the only treatment is a donor corneal transplant. This pathology is statistically more common among women;
• keratoconus - the stratum corneum becomes thinner and the cornea takes a conical shape. In advanced cases of the disease, the deformation is noticeable even with the naked eye. Typical complaints are blurry vision and split gaze if only one eye is affected by keratoconus. Pachymetry helps to determine the thickness of the cornea and the required depth of incisions during surgery;
• keratoglobus - the mechanisms of the development of the disease are similar to keratoconus. Due to the thinning of the main tissues, the eyeball protrudes and takes a globe-shaped shape;
• in preparation for laser correction vision patients undergo a pachymetry session without fail. This is necessary to know the thickness of the cornea and structural features buildings. Pachymetry is prescribed for other operations on the eyeball;
• postoperative observation also includes a stratum corneum thickness measurement routine. The examination is often prescribed after corneal transplant operations. Here pachymetry helps to control the engraftment of donor tissues and to respond promptly to complications.

Pachymetry has become a popular diagnostic method because it is suitable for many categories of patients. Due to its relative simplicity and safety, the procedure is also suitable for children who are able to sit quietly during the diagnosis.

Contraindications

There are few contraindications to pachymetry. This diagnostic method is undesirable for the following categories of patients:

The optical pachymetry process has no particular contraindications, since the diagnosis is made by a non-contact method.

IMPORTANT! People in drug, alcohol and other intoxication, patients with certain mental illness pachymetry is strongly prohibited. Alcohol delirium and narcotic withdrawal are also unacceptable during a diagnostic session. The specificity of this method assumes a direct gaze and immobility for some time.

The pachymetry procedure requires special attention to contraindications, since in case of gross violations, even the death of the patient is not excluded.

Normal corneal thickness

The thickness of the cornea in a healthy adult is 0.52 - 0.6 mm in the central part and 1 - 1.2 mm at the edges. The stratum corneum is thicker below the center than above. According to statistics, the thickness of the cornea in women exceeds that of men by an average of 0.09 mm.

REFERENCE! The diameter of the cornea increases from the moment of birth to 4 - 5 years. From a certain time the growth stops and remains constant.

Observations show that corneal thickness can change during the day. The permissible rate of change is up to 0.06 mm.

Preparation

No special training is required to perform non-contact optical pachymetry. All necessary preparations are made during the procedure.

An ultrasound procedure involves touching a special device to the surface of the eye. As a preparation, the ophthalmologist applies a local anesthetic. The most common pain reliever is Inocaine.

If the patient is wearing contact lenses, remove them before the examination. Recovery or rest after the diagnostic procedure is not required.

Research methods

Pachymetry techniques differ depending on the type of procedure and the instrument used. An important difference between diagnostic devices is the repeatability of the data. The repeatability of data should be understood as the possibility of obtaining a similar result when the survey is repeated. Many scientific publications suggest that the ultrasound pachymeter provides the most accurate and repeatable data. The repeatability of the final diagnostic result is very important, since only reproducible experience can be considered correct.

REFERENCE! In addition to the differences in techniques depending on the equipment, there are several ways to carry out diagnostics within one technique.

Since all methods are painless and comfortable, when choosing a diagnostic method, one should be guided by the doctor's recommendations.

Optical technique

When performing optical pachymetry, the sequence of actions is as follows. The slit lamp is fixed to the mount. A special attachment is installed on the surface of the lamp to observe the structures of the eyeball. The patient's head is fixed with fixing devices. The doctor asks the patient to stay still and not blink.

During the examination, the doctor directs a beam of light to the desired area and controls the pachymeter handle. The cornea is examined using two parallel lenses. The first lens is fixed, and the second is capable of changing the angle of inclination. Based on the characteristics of light refraction, the doctor measures the thickness of the cornea on a special scale. One turn of the glass plate of the pachymeter is respectively 0.1 mm.

Ultrasound examination

During the ultrasound pachymetry procedure, a contact probe is applied to the surface of the eyeball. Therefore, an anesthetic must be used before the procedure.

After the anesthesia is administered, the patient should lie on the couch and keep his eyes open. The doctor picks up a diagnostic device, leans it against the surface of the eye and carries out diagnostics.

About varieties

There are three approaches to eye diagnostics. Each of them has a certain technique and final informational content.

Optical

Despite more than half a century of history, this technique is often used to this day. The simplicity and efficiency of the optical method allows it to compete with the latest medical developments.

The key difference with this diagnostic method is the use of a slit lamp and several special lenses. The doctor uses a lamp as a microscope. A narrow strip of light is directed to the patient's eyes, which makes it possible to assess the structure of the eyeball under significant magnification.

Ultrasonic

The most common feature of ultrasound pachymetry is the use of a contact probe. The device generates ultrasonic waves that are able to propagate and reflect in tissues human body.

Behind the cornea is the anterior chamber of the eye, filled with intraocular fluid. Ultrasonic waves from the transducer pass through the stratum corneum and are reflected from the moisture layer. A detector located inside the device records the incoming data. Evaluation of the nature of propagation and frequency of reflected waves allows drawing conclusions about the current state of the stratum corneum.

After the end of the ultrasound pachymetry session, the patient may feel discomfort in the eyes. In this case, rinse your eyes with warm water. It should be noted that the diagnostic procedure is harmless. In most cases, the examined person does not feel any discomfort. Full eye sensitivity is restored 10 to 15 minutes after the end of pachymetry. The time it takes to recover varies with the type of anesthesia and the dose of the drug.

IMPORTANT! After the procedure, you need to drip antibacterial drugs into the conjunctival sac. Since the sensor is in contact with the surface of the eye, there is a risk of infection.

Ultrasound pachymetry has almost completely replaced optical pachymetry. Speed \u200b\u200band precision are the characteristic advantages of the contact method.

Computer

The essence of this technique is similar to ultrasound pachymetry. The difference lies in the hardware used. The method of computer diagnostics involves the use of a tomograph, which scans the studied areas of the human eye. Infrared radiation is used for scanning.

The study of the posterior wall of the cornea is widely used to reveal latent keratoconus.

The collected information goes to the computer, where it is processed within a few minutes. The ophthalmologist receives a ready-made image and data layout, after which he can consult the patient and make a diagnosis.

How much is?

The price range for diagnostic services is not too wide. The pachymetry method used is a key factor in price formation. average price by city Russian Federation - 700 rubles.

The lower threshold is 300 rubles. This is the cost of optical pachymetry services in inexpensive provincial clinics. The low price is due to the technical simplicity of the procedure and the use of outdated or inexpensive equipment.

The upper value of the cost is 3000 rubles and above. For this price, sessions of ultrasound or infrared pachymetry are performed in private and other clinics.

REFERENCE! For Moscow and St. Petersburg, it is necessary to increase the lower values \u200b\u200bof prices by one and a half to two times.

It should be noted that anesthetic and antibacterial drugs are not always included in the cost of diagnostics. Always clarify this nuance in order to avoid financial difficulties and misunderstandings.

Useful video

How is corneal pachymetry performed, what is normal thickness - the ophthalmologist talks about the research method:

Conclusion

Pachymetry is a reliable and comfortable ophthalmic diagnostic tool for patients. Due to the simplicity of the procedure and the small number of contraindications, similar method diagnostics are widely used in clinics and hospitals in every country.

The particular value of this technique lies in the instantaneous results obtained and the low cost of the examination. When there is persistent discomfort in the eyes or in case of a drop in visual acuity, it is recommended to immediately sign up for an ophthalmic diagnosis session.

remember, that best treatment - this is the early prevention of the disease.