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

Structure of the cornea of ​​the eye

The shape of the cornea resembles, it is convex-concave. The structure of the cornea consists of five layers, which are located from the outside to the 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 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 that provide immune protection against pathogenic microbes. Fibrocytes located in the stroma produce collagen, maintaining its balance.
4. Descemet's membrane is resistant to high temperatures and infections.
5. The single-layer endothelium is semi-permeable and allows nutrients coming from the aqueous humor to pass through. When the function of this layer is impaired, swelling occurs, which prevents normal nutrition of the cornea. 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 performs several functions:

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

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

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

Video about the structure of the cornea

Symptoms of corneal damage

Corneal pathology can be suspected based on the following symptoms:

• Changes in the shape of the cornea;
• Decreased visual acuity;
• His ;
• Pain in the eyeball;
• Narrowing of visual fields;

Diagnostic methods for corneal lesions

If a corneal pathology is suspected, it is necessary to conduct an examination:

• Side beam imaging;
• eyes;
• Bacteriological research;
• Keratotopography.

In case of 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 opacities of the cornea;
• 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 disrupted, dysfunction of both the cornea and the entire optical system occurs. In order to diagnose the pathological process in a timely manner, it is necessary to conduct additional examination methods. This will allow you to prescribe timely and effective treatment.

Using this method and biomicroscopy, the doctor can obtain information about the condition of the cornea, which is necessary for making a correct diagnosis and further treatment planning.

Data on corneal size in healthy people

The thickness of the cornea in the central zone of the eye, in the absence of obvious pathology, should have values ​​from 0.49 mm and not exceed 0.56 mm. In the limbal zone, the sizes are slightly different: from 0.7 mm to 0.9 mm.

In women, the average thickness of the cornea corresponds to 0.551 mm, in representatives of the stronger sex - 0.542 mm.

The dimensions of the cornea may undergo slight changes during the day and have a shift of 0.6 mm, but in no way exceed this figure. Otherwise, this may indicate the presence of pathology in the cornea.

Indications for use

The need for pachymetry may arise when:
Corneal edema;
;
and keratoglobus;
Fuchs' dystrophy;
To check the condition of the cornea after surgery on it in connection with its transplantation;
Before laser vision correction.

Contraindications

When diagnostics cannot be performed:
If the patient is in an inadequate state (under the influence of alcohol or drugs);
If the patient has mental illness in the acute stage;
When there are signs of a violation of the integrity of the cornea;
If the patient has purulent eye diseases.

The last two contraindications do not require ultrasound pachymetry.

Types of examination

Ophthalmologists distinguish several varieties of this technique.

Optical– refers to non-contact research, involves the use of a slit lamp.

An attachment is installed on an ophthalmic microscope (slit lamp), which allows you to determine the size of the cornea in different areas.

It is represented by two glass plates, which are located parallel to each other:

• The lower one is fixed, not subject to movement;
• The upper one has the ability to move vertically.

The nozzle must be perpendicular to the optical axis of the lamp. The patient being examined takes a position on one side of the lamp, touching his forehead and chin to special stands. The doctor is opposite the patient on the other side of the lamp.

The ophthalmologist examines the patient's eyes one by one, setting the light to the required position. At the same time, he turns the handle of the device and, using a special scale, measures the size of the cornea. A rotation of the plate by one degree is comparable to one millimeter of the cornea being examined.

Ultrasonic– refers to contact methods that use an ultrasonic device.

It is a more reliable and more accurate examination of the cornea compared to the optical method. Its indicators are more accurate by ten microns.

Before the procedure, preliminary anesthesia is performed. For these purposes, local anesthesia is performed using Inocaine, which is instilled into the eye being examined.

The patient takes a supine position on a special couch, the doctor numbs the eye area, and then the ultrasound machine nozzle touches the surface of the eye. It should put as little pressure on the cornea as possible, since excessive pressure can negatively affect the results of the study.

The monitor will independently receive the received data, perform calculations and display the results. After such a study, it is recommended to use antibacterial drugs, such as Albucid, for eye drops.

Where is pachymetry performed and its cost?

This study is carried out both in public medical institutions and in private ophthalmological offices and clinics.
On average, the cost of this examination is about 1000 rubles.

It is a diagnostic method of instrumental examination, which is used in ophthalmology. It can be used to measure the thickness of the cornea of ​​the eyeball.

Pachymetry is usually carried out together with, in order to obtain more information about the condition of the cornea, which is necessary for accurate diagnosis, and is also of great importance in terms of preoperative preparation.

Indications for measurement

The main indications for this study are:

• keratoglobus;
• Fuchs' dystrophy.

In addition, pachymetry is performed after surgical intervention, as well as as a preoperative examination before laser correction of the disorder.

Contraindications to pachymetry

Pachymetry can be dangerous in some situations, so it is not performed if:

• toxic effects of drugs or alcohol;
• mental illnesses accompanied by psychosis, agitation, inappropriate behavior, since the patient can harm the doctor or himself;
• violation of the integrity of the stratum corneum of the eyeball (contact examination is not performed);
• inflammatory and purulent eye diseases (ultrasound pachymetry is not performed).

Video about the procedure

Normal corneal thickness

The thickness of the cornea in its central part in a healthy person is 0.49 mm - 0.56 mm. In the limbic part, this figure is usually slightly higher (from 0.7 to 0.9 mm). There are also gender differences: in women, the average thickness of the corneal layer is usually slightly greater (0.551 mm) than in men (0.542 mm). Interestingly, during the day the thickness of the cornea can also change slightly (within 0.6 mm). If deviations of this indicator from the norm are detected, then additional examination is required to determine the cause of this condition.

Types of research

Corneal pachymetry is performed using two methods:

• optical (non-contact) is performed using a slit lamp or optical coherence tomograph (procedure) - coherence pachymetry;
• Ultrasonic (contact) measurement of corneal thickness is carried out using a special sensor and apparatus - ultrasound pachymetry.

Optical pachymetry

With optical pachymetry, you can measure the thickness of the stratum corneum of the eyeball without contact. In this case, a special attachment is placed on the slit lamp, with the help of which the value of this indicator is measured in various areas. During the examination, the patient is positioned on one side of the slit lamp. Special restraints are installed on his forehead and chin area. The doctor sits on the opposite side, where the optical output of the lamp, necessary for observation, is located. The special nozzle looks like two parallel glass plates, with one of them (the lower one) tightly fixed and motionless, while the upper plate can rotate vertically. The attachment for measuring corneal thickness should be positioned perpendicular to the intrinsic axis of the slit lamp.

When taking measurements, the doctor looks at the patient's eye under examination and directs the beam to the desired area by rotating the pachymeter handle. Using a special scale, the doctor measures the thickness of the cornea. In this case, 10 turns of the glass plate corresponds to 1 mm of the cornea.

Ultrasound pachymetry

With ultrasound pachymetry, direct contact of the surface of the cornea with the sensor of the device occurs. This technique is considered more accurate (up to 10 microns) when compared with the non-contact method. During the examination, the patient lies on a couch next to the device. Next, local anesthesia of the eye is performed using Inocaine drops. After this, a special sensor is placed on the surface of the cornea, trying not to squeeze the soft tissue of the eyeball and the corneal layer itself. If the contact is too tight, the results may be significantly distorted. The monitor displays an ultrasound picture, which makes it quite easy to take the necessary measurements and also record the results. After conducting a contact study, it is necessary to instill antibacterial drops (Tsipromed, etc.) into the conjunctival sac. This should be done to prevent possible infection.

Where is corneal thickness measured?

To perform a pachymetric examination of the cornea, you can contact any public or paid ophthalmology clinic that has the necessary equipment.

Ultrasound of the eye is a diagnostic research method that is used in ophthalmology to detect a wide range of eye diseases.

Ultrasound examination is absolutely safe and maximally informative compared to other diagnostic methods; in some cases, ultrasound of the eye is the main way to detect pathology and make a diagnosis.

Indications

Indications for ultrasound diagnostics of the eye:

• diagnosis of intraocular neoplasms, as well as monitoring their dynamics;
• eye injuries, except open wounds and burns;
• detection of a foreign body, determination of its location, mobility and other criteria;
• hypermetropia, myopia, presbyopia, sharp decrease in vision;
• glaucoma;
• cataract;
• retinal detachment or threatened retinal detachment;
• disorders and pathological processes in the extraocular muscles;
• pathology of the optic nerve;
• congenital pathologies;
• destruction of the vitreous body;
• exophthalmos;
• determination of the size of the lens and cornea;
• identification of blood clots, determination of their location, volume mobility;
• monitoring the condition of the eyes in case of diabetes, kidney disease and other chronic pathologies that have a negative impact on the visual organs;
• control when planning surgical operations, as well as postoperative control.

Contraindications

The founder of the ultrasound method of eye examination F.E. Friedman argued that this method has absolutely no contraindications. Ultrasound of the eye can also be performed on pregnant women, as well as women who are breastfeeding. There are no contraindications for the use of the diagnostic method in patients with oncological and hematological pathologies.

However, the use of ultrasound is prohibited for open eye wounds and burns - these are the only contraindications to the use of ultrasound of the organs of vision.

Preparing for the study

Before performing an ultrasound examination of the eyes, no preparation is required, unlike other diagnostic methods. Ultrasound of the visual organs does not require following a special diet, taking medications or undergoing additional tests.

The only preparation for women before an ultrasound is to remove makeup, but it is best to initially come to the procedure without wearing decorative cosmetics on your eyes and face.

Methodology

Ultrasound of the eye includes several different techniques, each of which has its own purpose. Ultrasound methods of the organs of vision:

1. A-method or one-dimensional echography - this technique is used to determine the size of the eye (such information is necessary before surgery), its structure, and elements. An anesthetic is instilled into the patient's eye to numb and immobilize the eyeball. The doctor moves the sensor not over the eyelid, but directly over the eyeball. The result of the study is displayed in the form of a graph with the parameters of the eyeball.
2. B-method or two-dimensional echography - the technique is used to study the characteristics of the internal structure of the organ of vision and obtain its two-dimensional picture. On the monitor, the doctor sees a display of a large number of light dots of varying brightness. This method involves performing an ultrasound through the upper eyelid; the procedure takes no more than 15 minutes.
3. A combination of A and B methods - this study includes the advantages of both methods, this allows you to make the diagnosis as accurate as possible.
4. Ultrasound biomicroscopy - this study is based on digital processing of echo signals, due to which the image on the monitor screen is displayed in high quality. The software used for this ultrasound method allows for interactive and a posteriori analysis of the displayed information.
5. Three-dimensional echography - this ultrasound method of eye diagnostics allows you to display a three-dimensional image of the structure of the organs of vision and the vascular system of the eye.
6. Power Dopplerography is a method used to determine the condition of the blood vessels of the eye by analyzing the speed and amplitude values ​​of blood circulation.
7. Pulse-wave Dopplerography - this method of diagnostic research is designed to analyze noise, this allows you to determine the exact speed and direction of blood flow in the vessels located in the organ of vision.
8. Duplex ultrasound examination - the technique allows, in one application, to determine the size and structure of the eyeball, as well as assess the condition of the vessels located in the eye, in other words, this method includes the advantages of other methods of ultrasound of the visual organ.

How is an ultrasound of the eye performed?

Performing an ultrasound of the eye using the A-method begins with superficial anesthesia - the patient sits in a chair to the left of the doctor, then the doctor instills an anesthetic into the eye, the anesthetic drug not only plays the role of anesthesia, it also ensures the immobility of the eye that will be examined. Next, a sterile sensor is placed on the surface of the eyeball, and the patient’s eyelids remain open.

Ultrasound examination of B-methods is performed through a closed eyelid, therefore in this mode anesthesia is not performed; a special gel is applied to the skin of the eyelid. Ultrasound of the eye using the B-method takes about 20 minutes; after the examination, the gel is washed off with a regular napkin.

What does an ultrasound show?

Evaluation of the results of an ultrasound examination occurs by comparing the information obtained during the diagnostic process with the norms, while the doctor identifies measurement parameters that make it possible to exclude pathological processes in the visual organ.

Normal indicators:

• the lens is transparent, it is invisible, but the posterior capsule of the lens is visible;
• the vitreous body is transparent;
• the length of the eye axis varies from 22.4 millimeters to 27.3 millimeters;
• with emmetropia, the refractive power of the eye varies from 52.6 to 64.21 D;
• the width of the hypoechoic structure of the optic nerve varies from 2 to 2.5 millimeters;
• thickness of the inner shells – 0.7-1 millimeter;
• the volume of the vitreous body is approximately 4 milliliters;
• the anterior-posterior axis is normally about 16.5 millimeters.

Ultrasound examination of the eye allows the ophthalmologist to obtain extensive information not only about the size of the eye and the position of its structures, it also provides information about the presence of foreign bodies, retinal detachment, dislocation and subluxation of the lens, neoplasms in the eye and in the orbit.

Ultrasound determines the anterior-posterior size, which is necessary to assess the dynamics of myopia or when selecting an artificial lens when prescribing a patient for cataract surgery.

Selection of contact lenses is a matter for a specialist

If you have problems with clearly seeing objects located in the distance, or cannot distinguish letters when reading at close range, or quickly get tired when working with papers, then you need to check your visual acuity and choose a method of vision correction. This article will discuss methods for selecting contact lenses that help solve many vision problems.

Why do you need an eye test?

In order to make a competent selection of contact lenses, you need to check your visual acuity and get a prescription from your doctor. This can be done in the office of an ophthalmologist. Today you can also check your eyesight over the Internet. There are many sites offering this service. However, you should not rely only on such data. Using a computer, you will determine the approximate visual acuity. At home, it is impossible to comply with all the conditions for conducting tests: illumination level, contrast, distance, size of characters, etc. In addition, you will not be able to find out which optical power lenses will provide the most comfortable and clear vision.

Only with the help of eye charts can an ophthalmologist make a correct diagnosis and write a prescription for glasses or contact lenses.

After all, decreased vision can be associated not only with myopia or farsightedness, but also with other eye diseases that cannot be identified on the Internet. It is the specialist who, in the course of studying refraction using a set of trial contact lenses, can determine which models are needed. There is also another method for measuring the refraction of the eye - this is skiascopy, read more here.

Methods for selecting contact lenses

The selection of contact lenses is based on a theoretical model, the so-called “sagittal size theory,” or sagittal depth - the distance from the top of the contact lens to the line connecting the edges of the lens. The success of lens selection is determined by the ratio of the sagittal size of the lens and the cornea. It is very difficult to measure this value in practice, so correspondence between the sagittal dimensions of the cornea and the lens is achieved by varying the radius and diameter of the lens.

Contact lenses with a smaller base radius or larger diameter are “cool”, i.e. less mobile; lenses with a larger base radius or smaller diameter are more flexible. In this case, 1 mm change in the diameter of the contact lens corresponds to a decrease or increase in the base radius by 0.3 mm.

Thus, lenses with a flatter radius and larger diameter are equivalent to lenses with a steeper radius and smaller diameter.

When manufactured through molding, lenses with aspherical geometric characteristics of the back surface are obtained. This means that the radius of curvature at the edges of the lens becomes larger (i.e. flatter), while the front surface remains spherical. The radius of curvature of the front surface is constant throughout the central part, the rear surface is modified to obtain the required optical power within one series. The molded lenses have a 1mm wide edge chamfer.

Molded lenses of different sagittal sizes are available in different series and with different diameters. Turned lenses are made with different base curves. Their diameter is constant, and this provides a wide selection of contact lenses for different corneas.

In addition to sagittal size, lens thickness and flexibility play an important role. The effect of sagittal size on fit becomes less significant with more flexible lenses.

When using two very thin lenses of different sizes, the fitting results are approximately the same. As a result, very thin lenses are made in only one sagittal size.

When selecting contact lenses, it is important to measure such eye parameters as:

• width of the palpebral fissure;
• position and condition of the eyelids.

Various methods for selecting SCLs have been proposed:

1. A method based on measuring the diameter of the cornea (proposed by Bausch & Lomb for molded contact lenses). Its essence is that for patients with a wide palpebral fissure, lenses with a large diameter (14.5 mm) are selected; for those with a “steep” cornea (45.0 D or more), lenses with a smaller diameter are selected.
2. Method based on measuring the radius of the cornea. It is mainly used for chiseled contact lenses. The essence of the method is that a flatter base lens radius (3.0-4.0 D) is selected taking into account the width of the palpebral fissure. For example, for lenses with a diameter of 13.5 mm with a corneal radius = 41.0 D, the base radius of the lens is 8.9 mm. Thus, this method allows you to choose the diameter of the lens so that its edge extends 1.0-1.5 mm beyond the limb.
3. The third method was first proposed by Cooper Vision for Permalens lenses (79%). Its essence is as follows: measure the radius and diameter of the cornea. So, for minus lenses, the selection should begin with a radius of 8.0 mm and a diameter of 13.5 mm (8.0/13.5). In this case, it is necessary to take into account the mobility of the lenses. If the lens is too steep, select sizes 8.3/13.5, if too flat - 7.7/13.5. For highly hydrophilic plus lenses, it is recommended to start with 8.3/14.0 lenses.
4. Method based on measuring the sagittal depth of the contact lens (Softcon 55%). Example: for corneal radius from 41.25 to 42.0 D, lenses with parameters 8.4/14.0 or 7.8/13.5 are recommended; for radius indicators from 44.5 to 45.5 D - lenses 8.1/14.0 or 8.4/14.5.
5. Selecting the refractive power of the lens. This parameter is determined based on the results of a study of the clinical refraction of the eye and taking into account the spherical equivalent.

1DAY ACUVUE TruEye contact lenses are the optimal choice for people leading an active lifestyle, all information is at this link.

Principles of selection of hard contact lenses

Lens thickness

It is known that there are lenses of different thicknesses. How to choose lenses according to this parameter?

In order not to make a mistake with the selection, you should take into account a number of individual characteristics of the patient, including the ability to handle a thin lens.

What nuances should you pay attention to?

• A thicker lens may be needed to improve vision for moderate astigmatism.
• When selecting a lens for a patient with low tear production, it should be remembered that a lens of standard thickness is less likely to dehydrate the eye than the thinnest lens and will be more effective when worn.
• When selecting contact lenses for corneas with flattening in the center (for example, after corneal injuries, refractive surgery), lenses with a greater thickness in the center (but not more than 0.2 mm) should be used.

When choosing a lens type, preference is given to a product that will provide better tolerance and more closely match the anatomical features of the eye.

The new soft lens must be rinsed with saline to remove the preservative, put on the eye and evaluate its compliance with the shape of the cornea, centering and mobility. If the lens is located centrally on the cornea, then its position is correct. Sometimes there is a slight downward or upward shift. Centrifugally molded lenses tend to decenter. However, if at the same time its mobility and good visual acuity are maintained, and the patient does not complain of discomfort, then the position of the lens on the eye can be considered correct.

Normally, the amplitude of movement of thin lenses should not exceed 0.5-1.0 mm; lenses of average thickness - 0.5-1.0 mm. The minimum mobility should be at least 0.5 mm in each direction.

The position of the soft lens on the eye can be determined using a fluorescein test. The test uses a special high molecular weight fluorescein, which, unlike an aqueous solution of fluorescein used for hard lenses, does not impregnate or stain the lenses. The examination is performed by a doctor using a slit lamp with a blue filter.

When the lens is optimally positioned on the eye, fluorescein is distributed evenly throughout the sublens space. If the dye is distributed predominantly at the periphery, then the lens fits “flat”; If the dye fills the central space, then the lens fit is “steep”.

If the fluorescein test is not possible, the thickness of the tear gap in various areas is determined by biomicroscopy using the method of direct focal illumination and slit cutting of the lens and cornea.

How is the eye's adaptation to a soft contact lens monitored?

1. The position of the lens and its mobility are roughly assessed immediately after putting the lens on the eye.
2. After 30 minutes, lacrimation decreases, the patient gets used to the lens, and the position of the lens on the eye, its mobility, and visual acuity are checked again.
3. The next step is to assess the mobility of the lens when looking up and down. When looking up, the bottom edge of the lens tends to move slightly down the sclera. When looking down, the lower eyelid moves the lens upward by approximately 2-3 mm. Less movement of the lens usually indicates a “steep fit”, and greater mobility usually indicates a “flat fit” of the lens.

Another way to check the correct position of the lens is with the displacement test. First, the doctor spreads the eyelids and with his finger moves the lens along the cornea by 1/3-1/2 of its diameter.

When seated well, the lens should slowly return to its center position. With a “flat” fit, a low or high position of the lens is observed when the limb is not covered by the lens along its entire circumference. In the case of a “steep” fit, the lens does not move well and quickly returns to the central position, while air bubbles, redness of the eyes, and decreased visual acuity may be observed in the space under the lens.

What disease is redness of the eyes a symptom of, see here.

Partial pressure of oxygen in the cornea when using a soft contact lens with a thickness of 0.2 mm and the diffusion ability of the lens with respect to oxygen. The eyelid is raised.

Trial set of soft lenses

Selection, as a rule, begins with standard lenses. For this purpose, sets of trial standard lenses are used. Such a set should contain lenses with a range of typical parameters and with different diopter powers. If the structure of the eye does not fit into the standard framework, then the manufacture of an individual contact lens will be required. In this case, it is recommended to use sets of trial lenses with slightly modified parameters.

After carefully assessing the position of the trial lens on the eye, adjustments are made to the design parameters of the lenses (base radius, optical power, diameter, thickness).

There are cases of poor tolerance to lenses with 40% moisture content. In such a situation, the doctor selects lenses with a higher moisture content (60-80%) or superthin lenses that have greater oxygen permeability. However, you need to know that these lenses are less durable and therefore less durable.

Video

Conclusions

As you can see, choosing contact lenses is not an easy task. And only an experienced specialist can do it correctly. Do not try to select lenses yourself, as you risk aggravating your vision problems and, moreover, adding new diseases.

This material will tell you how to properly care for contact lenses. If you feel dry eyes, be sure to use moisturizing drops, which are available, read in this section.

Pachymetry is an instrumental method of ophthalmological diagnostics that allows one to measure the thickness of the cornea of ​​the eye.

There are two types of pachymetry: optical (non-contact), which is performed using a slit lamp, and ultrasonic (contact), performed using an ultrasound machine.

When is pachymetry prescribed?

Indications for pachymetry are:

• Corneal edema.
• Inspection of the condition of the cornea after keratoplasty surgery.
• Preparation for surgical interventions (keratotomy, excimer laser vision correction).

Contraindications to pachymetry

This following method is not used if:

• The patient is under the influence of drugs or alcohol;
• The patient has a psychiatric illness accompanied by violent behavior (capable of harming both himself and the attending physician);
• The integrity of the cornea is compromised (for ultrasound pachymetry);
• A purulent process in the eye was detected (for ultrasound pachymetry).

Video from a clinic doctor about the research method

Carrying out pachymetry

The thickness of the cornea in the center of the eye is normally 0.49 - 0.56 mm. The thickness in the limbus area is slightly greater and is 0.7-0.9 mm. The average thickness of the cornea in women (0.551 mm) is greater than in men (0.542 mm). The average daily change in corneal thickness is possible within 0.6 mm; if this figure is higher, this indicates disturbances in its structure and requires careful examination.

Optical pachymetry

Non-contact method for measuring corneal thickness. When it is performed, a special attachment is put on a slit lamp (ophthalmological microscope), with the help of which the thickness of various parts of the cornea is measured. To do this, the patient's forehead and chin are placed in a special device in a sitting position, on the other side of which there is a doctor examining the eye. A special nozzle consists of two glass plates installed in parallel. In this case, the lower one is fixed motionless, and the upper one is capable of rotating along a vertical axis. The optical axis of the slit lamp is given a certain direction, perpendicular to which a special attachment is installed. The doctor, examining the patient's eye, moves the illumination to a given segment and, rotating the pachymeter handle, takes measurements of the thickness of the cornea, noting the indicators on a special scale. One degree of rotation of the nozzle plate corresponds to 1 mm of cornea.

Ultrasound pachymetry

This is a contact research method. Its results are more accurate compared to optical pachymetry (up to 10 microns). It is performed as follows: the patient is placed on a couch near the ultrasound machine, and a drip of anesthesia is given to the eye being examined. After this, they touch the surface of the eyeball with a hardware attachment, trying to have as little impact on the cornea as possible (this can slightly distort the results). The final results of the study are displayed on the monitor.