How optical coherence tomography of the eyes is performed. What is optical coherence tomography of the eye? Optical coherence tomography of the cornea

Optical coherence tomography a relatively new method for studying ocular structures.

It requires high-tech equipment and allows you to obtain comprehensive information about the condition of the retina and anterior structures of the eye without traumatic intervention. The infrared light beam does not cause damage or inconvenience during or after the diagnosis.

The very idea of ​​conducting diagnostics using infrared radiation was proposed only in 1995 by an ophthalmologist from the United States, Carmen Puliafito. The first device for optical coherence tomography appeared 2 years later. Today, this relatively new method of studying the eye is widely used.

Tomograph device for OCT

This is a high-tech device that consists of a device for producing low-coherence ultraviolet rays, reflective mirrors, a Michelson interferometer and computer equipment.

The rays generated by the device are divided into two beams, one passes through the eye tissue, and the other through special mirrors. The speed of passage of light rays is recorded and analyzed (radio waves are analyzed during ultrasound), but not direct ones (their speed is too high), but reflected ones.


Structures of the eye (skin, mucous membranes, lens, vitreous, veins, etc.) reflect light rays differently, this difference is recorded by the interferometer. The equipment converts numerical measurements into an image that is displayed on the monitor. Rays with high level reflections are drawn in a “warm” spectrum (red shades); the lower the reflection level, the cooler the color (up to dark blue and black). Thus, the vitreous body in the image will be black (it almost does not reflect light), and the nerve fibers (like the epithelium) have high degree reflections will appear red.

It follows that the study will be difficult in case of clouding of the optical media, corneal edema, and hemorrhages.

Scanning is carried out in two planes along and also across, many planar sections are made. This allows you to simulate an accurate three-dimensional picture of the eye. Resolution level from 1 to 15 microns. To study the bottom of the retina, a beam with a wavelength of 830 nm is used, to study the anterior part - 1310 nm.

The level of technical equipment today allows us to examine the anterior and posterior poles of the eye. To obtain high-quality diagnostic results, the optical media must be transparent and the tear film is normal (artificial tears are often used), the pupil must be dilated (special mydriatic drugs are used).

The obtained and deciphered result will be presented in the form of maps, drawings and protocols.

Many ophthalmologists refer to OCT as a non-invasive biopsy, which is essentially true.

When is coherence tomography prescribed?

I prescribe this examination for a number of diseases of the anterior part of the eye. Among them will be:

• various forms of glaucoma (examine and evaluate the performance of drainage systems),
• corneal ulcers,
• complex keratitis.

Coherence tomography is prescribed to study the anterior parts of the eye before and after:

• laser vision correction, keratoplasty,
• implantation of a phakic intraocular optical lens (IOL), or intrastromal corneal rings.

The posterior part of the eye is examined if:

• age, degenerative changes retina;
• macular holes or macular cystoid edema.

• if retinal detachment is suspected,
• in case of the presence of an epiretinal membrane (cellophane macula),
• for anomalies optic disc, ruptures, atrophies,
• with thrombosis of the central retinal vein,
• in case of suspicion of proliferative vitreoretinopathy or when it is detected.

Coherence tomography is often prescribed for patients with diabetic retinopathy (they are examined without mydriatics), as well as for a number of other ophthalmological diseases that require a biopsy.

Examination procedure using a coherence tomograph

The diagnosis itself is absolutely painless, it takes 2–3 minutes, and is carried out in a comfortable environment for the patient. The patient is placed in front of the fundus camera lens (the head is fixed) and looks at the flashing dot. If your vision is reduced and the point is not visible, then you just need to sit still and look at one point in front of you.

The operator will first enter patient data into the computer. Then the scan is carried out within 1-2 minutes. The patient is required not to move or blink.

After this, the received data is processed. The results obtained are compared with the data available in the database. healthy people, digital data is converted into maps and drawings that are easy to read. All results will be presented to the subject in the form of maps, tables and protocols.

Coherence tomography results

The interpretation of the results is carried out by a qualified specialist and will contain the following aspects:

• morphological features of tissues: external contours, relationship and ratio of various layers, structures and sections, connective tissues;
• light reflectance indicators: their changes, increase or decrease, pathologies;
• quantitative analysis: cellular, tissue thinning or thickening, volume of structures and tissues (here a map of the diagnosed surface is drawn up).

When examining the cornea, be sure to accurately indicate the location of the damage, its size and quality, and the thickness of the cornea itself. OCT allows you to very accurately determine the required parameters. Here great importance has a contact-free technique.

Diagnostics of the iris makes it possible to determine the size of the boundary layer, stroma and pigment epithelium. Although the signals from the lighter and more pigmented iris differ, in any case, they make it possible to identify diseases such as mesodermal dystrophy, Frank-Kamenetsky syndrome, and others at early (often preclinical) stages.

Coherence tomography of the retina will give a normal profile of the macula with a depression in the center. The layers must be uniform in thickness, without foci of destruction. Nerve fibers and pigment epithelium will have warm (red-yellow) shades, the plexiform and nuclear layers have average reflectivity, they will be blue and green, the photoreceptor layer will be black (it has low reflectivity), the outer layer will be bright red. The size measurements should be as follows: in the area of ​​the macula fossa a little more than 162 microns, at its edge - 235 microns.

Study optic nerve makes it possible to evaluate the thickness of the layer of nerve fibers (about 2 mm), their angle of inclination relative to the optic nerve head and retina.

Detection of pathologies using coherence tomography

During coherence tomography, many pathologies of both the anterior parts of the eye and the retina are detected. Studies of the retina and macula will be especially valuable, since the study allows us to determine the pathology as accurately as with a biopsy. But OCT is not invasive technique and does not violate the integrity of tissues. Thus, among the most frequently detected diseases are:

• Retinal defects, idiopathic breaks . They often occur in older people and occur for no apparent reason. The study establishes the focus, size at all stages of the disease, as well as degenerative processes around the focus, the presence of interaritinal cysts.
• Age-related macular degeneration. OCT allows you to identify these diseases (typical of the elderly), as well as evaluate the effectiveness of the therapy.
• Diabetic edema ranked among the most severe forms diabetic retinopathy is difficult to treat. Coherence tomography allows you to determine the affected area, the severity and degeneration of tissue, and the degree of damage to the vitreomacular space.
• Stagnant disk . The degree of light reflection determines hydration and tissue degeneration. The presence of a stagnant disc will indicate high intracranial pressure.
• Congenital defects of the optic fossa . Among them, delamination is the most common.
• Retinitis pigmentosa . Determining this progressive hereditary disease is often difficult. The method is very informative for babies, when other methods are powerless against the baby’s anxiety.

There are a limited number of ways to visualize the exact structure and minute details pathological processes in the structure of the organ of vision. The use of simple ophthalmoscopy is absolutely insufficient for a complete diagnosis. Relatively recently, since the end of the last century, optical coherence tomography (OCT) has been used to accurately study the state of eye structures.

OCT of the eye is a non-invasive safe method for studying all structures of the organ of vision in order to obtain accurate data on the smallest damage. No high-precision diagnostic equipment can compare with coherence tomography in terms of resolution. The procedure allows you to detect damage to ocular structures ranging in size from 4 microns.

The essence of the method is the ability of an infrared light beam to be reflected differently from different structural features eyes. The technique is close to two diagnostic procedures simultaneously: ultrasound and computed tomography. But in comparison with them it is significantly better, since the images are clear, the resolution is high, and there is no radiation exposure.

What you can explore

Optical coherence tomography of the eye allows you to evaluate all parts of the visual organ. However, the most informative manipulation is when analyzing the features of the following ocular structures:

• cornea;
• retina;
• optic nerve;
• front and rear cameras.

A particular type of study is optical coherence tomography of the retina. The procedure allows us to identify structural disorders in this ocular area with minimal damage. For examining the macular zone, the area of ​​greatest visual acuity, OCT of the retina has no full-fledged analogues.

Indications for manipulation

Most diseases of the organ of vision, as well as symptoms of eye damage, are indications for coherence tomography.

The conditions under which the procedure is performed are as follows:

• retinal tears;
• dystrophic changes in the macula of the eye;
• glaucoma;
• optic nerve atrophy;
• tumors of the organ of vision, for example, choroidal nevus;
• spicy vascular diseases retina – thrombosis, ruptured aneurysms;
• congenital or acquired abnormalities of the internal structures of the eye;
• myopia.

In addition to the diseases themselves, there are symptoms that are suspicious of retinal damage. They also serve as indications for research:

• sharp decrease in vision;
• fog or “floaters” before the eye;
• increased eye pressure;
• acute pain in the eye;
• sudden blindness;
• exophthalmos.

Except clinical indications, there are also social ones. Since the procedure is completely safe, it is recommended for the following categories of citizens:

• women over 50 years old;
• men over 60 years of age;
• everyone suffering from diabetes;
• in the presence of hypertension;
• after any ophthalmological interventions;
• in the presence of severe vascular accidents in the anamnesis.

How the research works

The procedure is carried out in a special room, which is equipped with an OCT tomograph. This is a device that has an optical scanner, from the lens of which infrared light beams are directed into the organ of vision. The scanning result is recorded on the connected monitor in the form of a layer-by-layer tomographic image. The device converts the signals into special tables, which are used to evaluate the structure of the retina.

No preparation for the examination is required. Can be done at any time. The patient, while in a sitting position, focuses his gaze at a special point indicated by the doctor. He then remains still and focused for 2 minutes. This is enough for a full scan. The device processes the results, the doctor evaluates the condition of the eye structures, and within half an hour a conclusion is issued on the pathological processes in the organ of vision.

Tomography of the eye using an OCT scanner is carried out only in specialized ophthalmology clinics. Even in large cities there is no large quantity medical centers offering the service. The cost varies depending on the scope of the study. A complete OCT of the eye is estimated at about 2 thousand rubles, only the retina – 800 rubles. If you need to diagnose both organs of vision, the cost doubles.

Since the examination is safe, there are few contraindications. They can be represented like this:

• any conditions when the patient is unable to fix his gaze;
• mental illnesses accompanied by a lack of productive contact with the patient;
• lack of consciousness;
• the presence of a contact medium in the organ of vision.

The last contraindication is relative, since after washing away the diagnostic medium, which may be present after various ophthalmological examinations, for example, gonioscopy, the manipulation is performed. But in practice, two procedures are not combined on the same day.

Relative contraindications are also associated with the opacity of the ocular media. Diagnostics can be carried out, but the images are not as high quality. Since no radiation occurs and there is no exposure to a magnet, the presence of pacemakers and other implanted devices is not a reason for refusal of examination.

Diseases for which the procedure is prescribed

The list of diseases that can be detected using OCT of the eye looks like this:

• glaucoma;
• retinal vascular thrombosis;
• diabetic retinopathy;
• benign or malignant tumors;
• retinal tear;
• hypertensive retinopathy;
• helminthic invasion of the organ of vision.

Thus, optical coherence tomography of the eye is an absolutely safe diagnostic method. It can be used in a wide range of patients, including those for whom other high-precision research methods are contraindicated. The procedure has some contraindications and is performed only in ophthalmology clinics.

Considering the harmlessness of the examination, it is advisable to perform OCT in all people over 50 years of age to identify minor structural defects of the retina. This will make it possible to diagnose diseases in the early stages and preserve quality vision longer.

Optical coherence tomography is a non-invasive (non-contact) method for studying tissue. It allows you to obtain higher resolution images compared to the results of ultrasound procedures. In essence, optical coherence tomography of the eye is a type of biopsy, only the first does not require taking a tissue sample.

A brief excursion into history

The concept on which modern optical coherence tomography is based was developed by researchers back in the 1980s. In turn, the idea of ​​​​introducing a new principle into ophthalmology was proposed in 1995 by the American scientist Carmen Puliafito. A few years later, Carl Zeiss Meditec developed a corresponding device, which was called Stratus OCT.

Currently, using the latest model, it is possible not only to study retinal tissue, but also optical coherence tomography coronary arteries, optic nerve at the microscopic level.

Research principles

Optical coherence tomography consists of generating graphic images based on measuring the delay period when a light beam is reflected from the tissues being studied. The main element of devices in this category is a superluminescent diode, the use of which makes it possible to form light rays of low coherence. In other words, when the device is activated, the beam of charged electrons is divided into several parts. One stream is directed to the area of ​​the tissue structure being studied, the other to a special mirror.

The rays reflected from objects are summed up. Subsequently, the data is recorded by a special photodetector. The information generated on the graph allows the diagnostician to draw conclusions about the reflectivity at individual points of the object under study. When assessing the next section of tissue, the support is moved to a different position.

Optical coherence tomography of the retina makes it possible to generate graphs on a computer monitor that are in many ways similar to the results of an ultrasound examination.

Indications for the procedure

Today, optical coherence tomography is recommended for diagnosing pathologies such as:

• Glaucoma.
• Macular tissue tears.
• Thrombosis of the blood vessels of the retina.
• Degenerative processes in the structure of the eye tissue.
• Cystoid edema.
• Anomalies in the functioning of the optic nerve.

In addition, optical coherence tomography is prescribed to evaluate the effectiveness of the therapeutic procedures used. In particular, the research method is indispensable in determining the quality of installation of a drainage device that is integrated into the eye tissue for glaucoma.

Features of diagnostics

Optical coherence tomography involves focusing the subject's vision on special marks. In this case, the operator of the device performs a series of sequential scans of tissues.

Significantly impede research and impede effective diagnostics pathological processes such as edema, profuse hemorrhages, and all kinds of opacities are capable of.

The results of coherence tomography are formed in the form of protocols that inform the researcher about the state of certain tissue areas, both visually and quantitatively. Since the obtained data is recorded in the device’s memory, they can subsequently be used to compare the condition of tissues before treatment and after the application of therapy methods.

3D visualization

Modern optical coherence tomography makes it possible to obtain not only two-dimensional graphs, but also to produce three-dimensional visualization of the objects under study. Scanning areas of tissue with high speed allows you to generate more than 50,000 images of the diagnosed material within a few seconds. Based on the information received, special software reproduces the three-dimensional structure of an object on the monitor.

The generated 3D image serves as the basis for studying the internal topography of the eye tissue. This opens up the possibility of determining clear boundaries of pathological neoplasms, as well as recording the dynamics of their changes over time.

Benefits of Coherence Tomography

Coherence tomography devices demonstrate the greatest effectiveness in diagnosing glaucoma. When using devices of this category, specialists are able to accurately determine the development factors of pathology in the early stages and identify the degree of progression of the disease.

The research method is indispensable when diagnosing such a common disease as macular degeneration, in which, as a result, age characteristics body the patient begins to see black spot in the central part of the eye.

Coherence tomography is effective in combination with other diagnostic procedures, for example, with fluorescent retinal angiography. When combining procedures, the researcher receives especially valuable data that helps make the correct diagnosis, determine the complexity of the pathology and select effective treatment.

Where can optical coherence tomography be performed?

The procedure is possible only with a specialized OCT device. Diagnostics of this kind can be resorted to in modern research centers. Most often, vision correction rooms and private ophthalmology clinics have such equipment.

Price issue

Carrying out coherence tomography does not require a referral from the attending physician, but even if it is available, the diagnosis will always be paid for. The cost of the study determines the nature of the pathology that the diagnosis is aimed at identifying. For example, determining macular tissue holes is estimated at 600-700 rubles. While tomography of the tissue of the anterior part of the eye can cost a patient at a diagnostic center 800 rubles or more.

As for complex studies aimed at assessing the functioning of the optic nerve, the condition of the retinal fibers, and the formation of a three-dimensional model of the visual organ, the price for such services today starts from 1,800 rubles.

One of the main tasks of any branch of medicine is to make a correct, accurate and, most importantly, timely diagnosis. In order to effectively cope with this task, specialists are constantly improving their technologies. If we talk about ophthalmology, it is worth noting that the eye has a very complex structure and the finest tissues. Until the 90s of the last century, X-rays or ultrasonography. Now one of the most modern and safe technologies is. The first optical coherence tomograph was created in 2001.

Operating principle of optical coherence tomography

According to the principle of its operation, tomography is similar to ultrasound, but instead of sound waves, OCT uses optical radiation in the near-infrared wavelength range. In other words, the OCT method uses a low-intensity laser beam.

The Konovalov Center now uses an optical coherence tomograph (OCT) using RTVue processing technology, in which the diagnostic beam reflected from the retina is processed using Fourier Domain OCT analysis. The RTVue system allows you to obtain images of retinal tissue at high speed in a non-invasive way and high resolution scans.

Advantages of using optical coherence tomography

The use of OCT has a number of clear advantages. The study is completely non-invasive, i.e. The tissues of the eye are not injured at all. With the OCT method, the ophthalmologist obtains two- and three-dimensional images of the fundus of the eye. It is important to note that all scanograms obtained not only reflect the structure of the fundus tissues, but also show functional state fabrics. The resolution of optical coherence tomography is about 10-15 microns (this is a 10 times clearer picture than when using other methods of studying the retina), which makes it possible to see individual cellular layers of the retina in the images and determine the disease at its core. early stage its development.

Optical coherence tomography is well suited for diagnosing retinal detachment, retinal dystrophy, etc. Many doctors recognized the high diagnostic value this method for diseases of the retina. IN ophthalmological center Professor Konovalov uses only the most modern equipment and techniques that will not only restore your vision, but also prevent the occurrence of such problems.